chapter 12 the circulatory system - tdchristian...

The Circulatory SystemCHAPTER

12

Your heart is only about the size of an adult’s closed fi st, but it beats about 100 000 times a day, delivering oxygen and nutrients via blood to every organ, tissue, and cell in your body. Th e heart functions along with a complex network of blood vessels—arteries, veins, and capillaries—that laid end-to-end would circle Earth twice! Th ese structures make up the circulatory system.

An imaging technology known as Magnetic Resonance Angiography (MRA) enables us to examine the circulatory system in great detail. In this image, you can see the chest and neck arteries (in red), the heart (lower centre), and the lungs (in orange, on either side of the heart). Th is is one example of how technology has increased our understanding of how body systems work, and how it is helping doctors diagnose and treat disorders of the heart and blood vessels.

Specifi c Expectations In this chapter, you will learn how to…

• E1.1 evaluate the importance of various technologies to our understanding of internal body systems

• E1.2 assess how societal needs lead to scientifi c and technological developments related to internal systems

• E2.1 use appropriate terminology related to animal anatomy

• E2.2 perform a laboratory or computer-simulated dissection of a representative animal, or use a mounted anatomical model, to analyze the relationships between the respiratory, circulatory, and digestive systems

• E2.3 use medical equipment to monitor the functional responses of the circulatory system to external stimuli

• E3.3 explain the anatomy of the circulatory system and its function in transporting substances that are vital to health

• E3.4 describe some disorders related to the circulatory system

476 MHR • Unit 4 Animals: Structure and Function

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Launch Activity

Listen to Your HeartWhat is the function of your heart? Why do you need blood to circulate to all the parts of your body? Does your heart always beat at the same rate? In this activity, you will listen to your own heartbeat using a stethoscope and explain what you are hearing, and why.

Safety Precautions• Students with heart problems should not be subjects in this activity.• Clean the earpieces of the stethoscope with alcohol and an absorbent

swab before and aft er each use.

Materials• alcohol • stethoscope• absorbent swabs • stopwatch

Procedure 1. Work in small groups, so everyone has a chance to listen to their

own heartbeat. 2. Have each person in your group sit quietly for a few minutes, and

then listen to their own heartbeat with the stethoscope. Try listening to the heartbeat at several diff erent places on the chest.

3. Taking turns, have each person do a few jumping jacks or walk around the classroom a few times. Th en, have the person sit down and listen to their own heartbeat again. Again, try listening to the heartbeat at several diff erent places on the chest.

Questions 1. Describe in your own words the heart sounds that you heard aft er

exercise. How did they diff er from the sounds you heard before exercise? 2. Why do you think the heartbeat sounds diff erent aft er exercise? 3. List some activities that you think might increase a person’s

heartbeat. Are there any activities that you think might decrease a person’s heartbeat?

4. Draw a diagram of a chest and indicate where you heard the clearest sound.

Chapter 12 The Circulatory System • MHR 477

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SECTION

12.1

Key Terms

circulatory system

heart

blood vessel

blood

open circulatory system

closed circulatory system

pulmonary artery

pulmonary vein

aorta

atrioventricular valve

semilunar valve

pulmonary circulation

systemic circulation

cardiac circulation

vasodilation

vasoconstriction

The Function of Circulation

In single-celled organisms such as an amoeba, nutrients and respiratory gases enter the cell and waste materials leave the cell by diff usion and other cellular processes. Th us, single-celled organisms exchange matter directly with the outside environment. In multicellular organisms, such as humans, the process of matter exchange is more complex.

Th e trillions of specialized cells in a multicellular organism are organized into functional, structural units, such as tissues and organs. Th e individual cells that make up these structural units require nutrients and oxygen, and they must rid themselves of wastes, just as single-celled organisms do. Th us, an effi cient system for transporting materials within the body is necessary. Th e circulatory system is this transportation system.

Main Functions of the Circulatory SystemTh e circulatory system has the following three main functions: 1. It transports gases (from the respiratory system), nutrient molecules, and waste

materials (from the digestive system). 2. It regulates internal temperature and transports chemical substances that are

vital to health from one part of the body to the other. 3. It protects against blood loss from injury and against disease-causing microbes

or toxic substances introduced into the body.

Major Components of the Circulatory SystemTh e circulatory system has three major components: the heart, the blood vessels, and the blood. Th e heart is a muscular organ that continuously pumps the blood through the body and generates blood fl ow. Th e blood vessels are a system of hollow tubes through which the blood moves. Together, the heart and blood vessels comprise the cardiovascular system (cardio comes from a Greek word meaning “heart,” and vascular comes from a Latin word meaning “vessel”). Blood is the fl uid that transports nutrients, oxygen, carbon dioxide, and many other materials throughout the body.

The Two Types of Circulatory SystemsMany invertebrates have an open circulatory system. Th e system is called “open” because blood fl ows freely within the body cavity and makes direct contact with organs and tissues. In other words, there is no distinction between the blood and the interstitial fl uid. In invertebrates, such as insects and crustaceans, the mixture of blood and fl uids that surrounds the cells is called hemolymph.

In an insect such as the grasshopper in Figure 12.1 (A), hemolymph is pumped through a single vessel that runs from the head to the abdomen. In the abdomen, the vessel divides into chambers that function as the insect’s heart. Tiny holes in the heart wall, known as ostia, allow hemolymph to enter the heart chambers from the body cavity. Th e hemolymph is pushed from one chamber to the next by muscle contractions. Nutrients and wastes are exchanged between the hemolymph and cells in the heart chambers before the hemolymph passes back into the transporting vessel to be eliminated from the insect’s body.

circulatory system the system that transports blood, nutrients, and waste around the body

heart the muscular organ that pumps blood via the circulatory system to the lungs and body

blood vessel a hollow tube that carries blood to and from body tissues

blood the bodily fluid in which blood cells are suspended

open circulatory system a circulatory system in which vessels open into the animal’s body cavity


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Open Circulatory Systems

The Two Types of Circulatory Systems

Closed Circulatory Systems

Grasshopper

Earthworm

Hemolymph

Bodycavity

Lateral hearts

Heart

Heart

A

B

Figure 12.1 (A) A grasshopper has an open circulatory system. The heart pumps hemolymph through a single tubular vessel into the body cavity. The fluid re-enters the vessel through small pores, called ostia. The arrows show the movement of hemolymph. (B) The earthworm has a simple closed circulatory system. Five aortic arches near the head act as hearts to pump the blood around the body.

Other animals, such as all vertebrates, earthworms, squid, and octopus, need a system to circulate the blood, keep it under pressure, and pump it at a speed suffi cient to supply the metabolic needs of all parts of the body. Th is type of system, called a closed circulatory system, keeps the blood physically contained within vessels and separate from other body tissues, as shown in Figure 12.1 (B). Th e blood follows a continuous fi xed path of circulation and is confi ned to a network of vessels that keeps the blood separate from the interstitial fl uid.

closed circulatory system a circulatory system in which the circulating blood is contained within vessels and kept separate from the interstitial fluid


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superiorvena cava

right pulmonary arteries

right lung

right pulmonary veins

right atrium

tricuspid valve

inferior vena cava

aorta

pulmonary valve

left pulmonaryarteries

pulmonarytrunk

left pulmonaryveins

left lung

left ventricle

left atrium

to bodyfrom body

to body

mitral valveaortic valve

from body

right ventricle

Figure 12.2 The human heart has four chambers. The arrows show the directions in which blood moves into, through, and out of the heart.

The Human Circulatory System: The HeartYour heart is located slightly to the left of the middle of the chest and is about the size of your fi st. Th e walls of the heart are made of a unique type of muscle called cardiac muscle. Cardiac muscle cells are arranged in a network that allows the heart to contract and relax rhythmically and involuntarily without becoming fatigued. In addition to pumping blood, a healthy heart also ensures that blood keeps fl owing in one direction only, and that oxygen-rich blood is kept separate from oxygen-poor blood.

The Structure of the HeartTh e human heart, like the hearts of all mammals and birds, has four chambers—a top chamber and a bottom chamber on both the right and left sides. Th e two top chambers, the atria (singular atrium), fi ll with blood returning from the body or the lungs. Th e two bottom chambers, the ventricles, receive blood from the atria and pump it out to the body or the lungs. Th e atria and the ventricles are separated from each other by a thick muscular wall called the septum.

Figure 12.2 shows some of the external and internal structures of the human heart.(Note that the right side of the heart is shown on the left in the diagram, and the left side appears on the right. Th is is the customary way to display the cardiovascular system, as if the heart is in someone who is facing you.)


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opening for coronary artery

fibrous skeleton

aortic semilunar valve

cross-sectionpulmonary semilunar valve

tricuspid atrioventricular valve

bicuspid (or mitral)atrioventricular valve

The Four Chambers of the HeartTh e right side of the heart receives blood that is coming back from the body, and then pumps this blood out to the lungs. Two large vessels, called the vena cavae (singular vena cava), open into the right atrium. Th e superior vena cava collects oxygen-poor blood coming from the tissues in the head, chest, and arms. Th e inferior vena cava collects oxygen-poor blood coming from the tissues elsewhere in the body. Th e oxygen-poor blood fl ows from the right atrium into the right ventricle, and then out into the pulmonary trunk. From there, it enters the left and right pulmonary arteries. It then continues to the left and right lungs for gas exchange. (Th e pulmonary arteries are the only arteries in the circulatory system that contain oxygen-poor blood.)

Th e left side of the heart does the reverse. It receives oxygen-rich blood from the left and right lungs and pumps this blood out to the body. Th e oxygen-rich blood fl ows from the lungs through the pulmonary veins to the left atrium. (Th ese are the only veins in the circulatory system that contain oxygenated blood.) Th e left atrium pumps blood into the left ventricle, where all the blood going to the body tissues leaves through the largest vessel in the body, the aorta. You will examine the route of blood fl ow in more detail later in this section.

As you can see in Figure 12.3, the heart has four valves inside it. Th ese valves ensure that blood fl ows in the correct direction. Th e atria and ventricles are separated from each other by two valves called atrioventricular valves. Th e atrioventricular valve on the right side is called the tricuspid valve because it is made up of three fl aps. Th e atrioventricular valve on the left side is called the bicuspid valve (or mitral valve) because it has only two fl aps. Th e other two valves are called semilunar valves because of their half-moon shape.

pulmonary artery large blood vessel that carries blood from the heart to the lungs

pulmonary vein blood vessel that carries blood from the lungs to the heart

aorta an artery that carries blood directly from the heart to other arteries

atrioventricular valve a valve in the heart between the ventricle and atrium

semilunar valve a valve between the ventricle and the large arteries; it carries blood away from the heart

Figure 12.3 This cross section of the human heart shows the four main valves that help maintain blood pressure and keep the blood flowing in one direction.

1. What are the three main functions of the circulatory system?

2. What is the main diff erence between open and closed circulatory systems?

3. Explain how hemolymph in the open circulatory system of an insect moves through its body.

4. If the left ventricle was not able to pump blood properly, what eff ect would this have on the lungs?

5. Describe the oxygen content (O2-rich or O2-poor) of the blood in each of the four chambers of the heart.

6. Describe the destination of the blood leaving each of the four chambers of the heart.

Learning Check


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A B

C

middle layer

outer layer

Artery

valve

inner layer

Vein

Capillary

smaller arteriessmaller veins

venules arteriolescapillaries

direction ofblood flow

large veins large arteriesHeart

Blood VesselsTh ere are three main types of blood vessels in the human body, as shown in Figure 12.4. Arteries carry blood away from the heart, and veins carry blood toward the heart. Smaller-diameter arteries are called arterioles, and smaller-diameter veins are called venules. A network of capillaries joins the arteries and arterioles with venules and veins. Th e one-cell-thick capillaries are the sites where gases, nutrients, and other materials are transferred from blood to tissue cells and from tissue cells to blood. Figure 12.4 Arteries (A) and

veins (B) have three layers. The outer layer is a covering of connective tissue mixed with elastic tissue. The middle layer consists of alternating circular bands of elastic tissue and smooth muscle tissue. The inner layer is only one cell thick and consists of flat, smooth cells. The shape and texture of these cells reduce friction as blood moves through the blood vessels. Capillaries (C) consist of a single layer of cells.

Explain what the black arrows in this figure indicate.

Figure 12.5 The diameter of a capillary is so small that red blood cells can only pass through these vessels one at a time.

Figure 12.6 This diagram shows the pattern of blood flow through vessels in a closed circulatory system.

An artery has highly elastic walls. Th is elasticity allows the artery to expand as a wave of blood surges through it during the contraction of the ventricles, and then to snap back during the relaxation of the ventricles. Th e expansion and contraction of the artery walls keeps the blood fl owing in the right direction and provides an additional pumping motion to help propel the blood through the blood vessels. When you measure your pulse, what you feel is the rhythmic expansion and contraction of an artery as blood moves through it.

Veins have thinner walls than arteries and a larger inner circumference. Veins are not as elastic as arteries, and they cannot contract to help move the blood back to the heart. Instead, the contraction of muscles keeps the blood in the veins fl owing toward the heart. Veins also have one-way valves that prevent the blood from fl owing backward. Th ese one-way valves are especially important in your legs because they ensure that the blood fl ows upward to your heart, against the downward pull of gravity.

Capillaries are the smallest blood vessels. Capillaries are spread throughout the body in a fi ne network. Th e capillary wall is a single layer of cells, and the average diameter of a capillary is about 8 µm, which is just large enough for the largest blood cells to pass through in single fi le (see Figure 12.5). Figure 12.6 shows an overview of the fl ow of blood through all vessels in a closed circulatory system.

Magnification: 500×


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blood vessels in lungs

pulmonary arteryleading to lungs

vein leading awayfrom body

pulmonary vein leadingaway from lungs

artery leading to body

rightventricle

left atrium

aorta

leftventricle

right atrium

blood vessels in body

The Mammalian Circulatory System: A Closer LookMammals have complex body systems with a high demand for energy. Th eir circulatory systems must be able to deliver oxygen rapidly and in large amounts. A mammal’s circulatory system must also carry waste products away from the cells quickly. To meet these needs, mammals keep oxygen-rich and oxygen-poor blood fl owing separately through what is known as a double circulatory system. It is called “double” because blood is pumped through one circuit between the heart and the lungs, and it is pumped through a second circuit between the heart and the rest of the body, as illustrated in Figure 12.7.

Th e movement of blood from the heart to the lungs, and then from the lungs back to the heart again, is called pulmonary circulation. Th e blood that fl ows from the heart to the lungs carries waste carbon dioxide gas (shown as blue in Figure 12.7). As this blood passes through the respiratory surfaces of the lungs, gas exchange takes place—carbon dioxide leaves the blood and oxygen moves into the blood. Th e freshly oxygen-rich blood (red) goes back to the heart and is pumped from the heart into a second circuit that transports it throughout the rest of the body. Systemic circulation takes oxygenated blood from the heart to other tissues and organs throughout the body. Aft er circulating throughout the body, the blood returns to the heart carrying waste carbon dioxide from the body’s tissues. Th e blood then re-enters the pulmonary circulation.

At any given time, between 80 and 90 percent of your blood is in systemic circulation. Most of the remainder is in pulmonary circulation. Th e heart itself is supplied by blood vessels that are in the heart muscle. Th e movement of blood through the heart tissues is called cardiac circulation.

pulmonary circulation the path that blood follows from the heart to the lungs and back to the heart

systemic circulation the path that blood follows from the heart to the body and back to the heart

cardiac circulation the movement of blood through the heart tissues

Figure 12.7 In a double circulatory system, blood flows from the heart through two different circuits—one passes through the lungs, and the other passes throughout the rest of the body.


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plasma 55%

white blood cellsand platelets 1%

red bloodcells 44%

Blood and Its ComponentsAn average adult human has about 5 litres of blood moving continuously through the circulatory system. Blood is sometimes called a connective tissue because it links all the cells and organs in the body. It is considered to be a tissue even though (unlike most of the body tissues) it appears to be a fl uid. In fact, blood consists of two distinct elements: a fl uid portion and a solid portion. Th e fl uid portion, called plasma, consists of water plus dissolved gases, proteins, sugars, vitamins, minerals, and waste products. Plasma makes up about 55 percent of the blood volume. Th e solid portion of the blood, the formed portion, consists of red blood cells, white blood cells, and platelets. Th ese cells and platelets are produced in the bone marrow, which is inside the bones. Th e formed portion makes up the other 45 percent of the blood volume, as shown in Figure 12.8.

Plasma and Its FunctionsPlasma is a clear, yellowish fl uid composed of about 92 percent water and 7 percent dissolved blood proteins. Th e remaining 1 percent of plasma consists of other organic substances and inorganic ions such as sodium, potassium, chloride, and bicarbonate. Th e main proteins in blood are albumin, globulins, and fi brinogen. Table 12.1summarizes the components of blood and their major functions in the body. Other substances transported by the blood include nutrients (glucose, fatty acids, and vitamins), respiratory gases (O2 and CO2), and the waste products of metabolism.

Table 12.1 Components of Blood Plasma and Their Functions

Component Major Functions

Water • Dissolves and transports other substances

Plasma proteins • Maintain fl uid balance in plasma, in cells, and in spaces between cells

• Help maintain slightly alkaline pH• Fibrinogen helps with blood clotting• Globulins (antibodies) strengthen immunity

Salts (ions)bicarbonatecalciumchloridemagnesiumpotassiumsodium

• Maintain fl uid balance in plasma, in cells, and in spaces between cells

• Help maintain slightly alkaline pH• Assist in nerve and muscle function

Red Blood Cells and Their FunctionsRed blood cells, also called erythrocytes, make up approximately 44 percent of the total volume of blood. (“Erythrocyte” comes from two Greek words, erythros for red, and kytos for hollow.) Red blood cells are specialized for oxygen transport. Th e oxygen-carrying capacity of the blood is dependent on the number of erythrocytes that are present and the amount of hemoglobin that each red blood cell contains.

A mature mammalian erythrocyte is a disk-shaped cell with no nucleus, as shown in Figure 12.9. Each cell is packed with about 280 million iron-containing molecules of the respiratory protein hemoglobin. Large quantities of oxygen can be transported in the blood because hemoglobin has special properties that allow it to pick up, or chemically bind with, oxygen. Hemoglobin releases oxygen in the presence of cells that need it. As mentioned in Section 11.2, hemoglobin also transports some of the carbon dioxide waste from cells. Aft er carbon dioxide diff uses into the blood, it enters the red blood cells, where a small amount binds to hemoglobin.

Figure 12.8 The three main components of blood can be separated using a device called a blood centrifuge. When the blood is separated, it briefly settles into layers, as shown here.

Figure 12.9 Mammalian red blood cells are shaped like bi-concave disks. This provides more surface area for gas exchange. A healthy body produces up to two million new red blood cells every second.



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Five Main Types of Leukocytes


Neutrophil


Eosinophil


Lymphocyte


Monocyte


Basophil

Gra

nulo

cyte

sA

gran

uloc

ytes

White Blood Cells and Their FunctionsWhite blood cells, also called leukocytes, are part of the body’s response to infection. Leukocytes make up about 1 percent of your total blood volume, but this may increase to more than double normal levels when your body is fi ghting an infection. All white blood cells have nuclei and appear to be colourless.

Th ere are fi ve main types of white blood cells, as shown in Figure 12.10. Together, they fi ght infections and cancer. Some of these leukocytes attack pathogens by a process known as phagocytosis, which means that they engulf and destroy pathogens. Cells that carry out phagocytosis are called phagocytes. Neutrophils are the most abundant leukocytes and are found in the body tissues of an animal as well as in the blood. Eosinophils are found in the mucous lining of the digestive and respiratory tracts. Basophils aid in immunity by secreting substances that attract phagocytes to destroy pathogens. Some lymphocytes produce proteins called antibodies that incapacitate pathogens and allow them to be easily detected and destroyed. Monocytes circulate in the bloodstream for only a few days before they become specialized as macrophages, which destroy bacteria.

Figure 12.11 Strands of fibrin form a mesh over a damaged blood vessel, thus trapping red blood cells and producing a clot.

Infer two reasons why clot formation is important.

Figure 12.10 Leukocytes move through the interstitial fluid, suspended in the blood plasma. For every white blood cell in normal human blood, there are about 500 to 1000 red blood cells. Neutrophils, eosinophils, and basophils are known as granulocytes due to the grainy appearance of their cytoplasm. Lymphocytes and monocytes are known as agranulocytes because of their smooth cytoplasm.

Platelets and Their FunctionsPlatelets (also called thrombocytes) are the third major substance in the formed portion of the blood. Platelets are membrane-bound fragments of cells that form when larger cells in the bone marrow break apart. Platelets do not contain nuclei and they break down in the blood within 7 to 10 days aft er they have formed. Platelets play a key role in clotting blood, which prevents excessive blood loss aft er an injury. Blood clotting is a complex process that involves several steps. Th ese steps, the result of which is shown in Figure 12.11, can be summarized as follows:• When a blood vessel is broken due to injury, it releases chemicals that attract platelets

to the site of injury.• Th e platelets rupture, releasing chemicals that combine with other chemicals in the

plasma to produce the enzyme thromboplastin.• As long as calcium ions are present, thromboplastin reacts with prothrombin

(a protein made by the liver) to produce another enzyme called thrombin.• Th rombin reacts with fi brinogen (another plasma protein) to produce fi brin.

Fibrin is an insoluble protein that forms a fi brous mesh over the site of injury. Th is mesh prevents the loss of blood cells and eventually solidifi es to form a clot.



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7. Use Figure 12.4 to explain why veins have valves. 8. Do all arteries carry oxygen-rich blood and all veins

carry oxygen-poor blood? Explain your answer. 9. Describe one function of each of the three main

types of blood vessels.

10. When a person exercises, one of the physiological responses is an increase in blood fl ow. In terms of the circulatory system, describe what is happening.

11. Compare an artery with a vein structurally. 12. Provide details about the three main components

of blood.

Learning Check

The Functions of BloodTh e functions of blood include acting as a medium for transporting materials in the body and regulating the concentration of substances and heat in the body.

TransportBlood is closely connected to the function of the digestive system. For example, blood in capillaries in the walls of the small intestine absorb many of the nutrients that are end products of digestion. Blood also absorbs nutrients that are synthesized by cells in parts of the body other than the digestive tract. Th ese nutrients, which include glucose and amino acids, are carried to the liver, where they are converted into storage products for transport to other parts of the body. As well, blood picks up chemicals and gases through the respiratory system and carries them throughout the body to where they are needed.

Blood also transports and removes the waste products of cellular processes. Blood carries excess amounts of various mineral ions (which are the end products of protein metabolism) and other waste products to the kidneys for processing and excretion. It also carries carbon dioxide, another waste product of cells, to the lungs, where it is then released.

The Cellular Components of BloodTable 12.2 compares the features of the main components in the formed portion of human blood. Note the diff erences in the form and function of these cells, even though they all belong to the same tissue.

Table 12.2 Comparing the Cellular Components of Blood

Point of Comparison Red blood cells

White blood cells

PlateletsGranulocytes Agranulocytes

Origin red bone marrow red bone marrow thymus, red bone marrow red bone marrow, lungs

Cells present per mm3 of blood (approximate)

5 500 000 (male) 4 500 000 (female)

6000 2000 250 000

Relative size small (8 μm diameter) largest (up to 25 μm) large (10 μm) smallest (2 μm)

Function to carry oxygen and carbon dioxide

to and from cells

to engulf foreign particles to play a role in the formation of antibodies

(defence function)

to play a role in the clotting of blood

(defence function)

Life span 120 days a few hours to a few days unknown 2–8 days

Appearance

basophil neutrophileosinophil monocytelymphocyte


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skin

air orwater

heat dissipatesacross skin

deep artery

deep vein

surface vein

heat flow

capillaries37

2820

20

20

20

20

34

20

A

B

Temperature RegulationTemperature regulation involves balancing the loss of heat from the body with the production of heat by metabolic processes. A mammal’s circulatory system is able to control heat loss by changing the volume of blood fl owing near the body surface. Under the control of the nervous system, blood vessels in the skin can either expand to carry more blood or constrict to carry less blood, as shown in Figure 12.12. An increase in blood fl ow by widening or dilating the vessels is called vasodilation. Th is occurs when the core of the body becomes hot as a result of vigorous activity or a high external temperature. Th e body has several mechanisms for releasing heat, including the evaporation of water in sweat. If the body needs to rid itself of excessive heat through perspiring, such as during a fever, dehydration can be a serious problem. Vasodilation helps the body to lose heat more rapidly.

A decrease in the fl ow of blood by narrowing or constricting the blood vessels near the surface of the skin is called vasoconstriction. Th is reduces the amount of heat that is dissipated from the skin, and helps the body to conserve heat. At the same time, waves of muscle contraction, called shivering, increase the production of heat by cellular metabolism. Th e heat this produces is spread through the body by the blood.

Vasoconstriction and vasodilation are controlled by a number of factors. In some cases, they may be triggered by the brain in response to changes in blood pressure. If the blood pressure is too high, vasodilation will reduce it. If the blood pressure is too low, vasoconstriction will increase it. Vasodilation and vasoconstriction may also be triggered by increased metabolic activity. Exercise, for example, results in vasodilation to increase the blood fl ow to the tissues. Some substances can interfere with the body’s internal temperature regulation mechanisms by promoting either vasodilation or vasoconstriction. Alcohol and nicotine, for example, promote vasodilation and cause blood to rush to the surface of the skin.

Under normal conditions, a counter-current heat exchange system helps to maintain a steady temperature in the core of the body. Th is system works because the deep arteries and veins entering and leaving the body’s extremities lie adjacent to one another, so the warmer blood that fl ows from the body core to the extremities exchanges heat with the cooler blood returning from the extremities to the body core. Blood returning from the extremities can fl ow either through a surface vein or through a deep vein. Figure 12.13 illustrates how the counter-current exchange mechanism regulates the temperature in your arm. Keep in mind that the extremities and the skin are not kept at 37°C. Th e temperature of these parts of the body may be signifi cantly below the internal core temperature.

vasodilation the widening of the blood vessels

vasoconstriction the narrowing of the blood vessels

Figure 12.12 (A) During vasodilation, the blood vessels expand, increasing blood flow near the skin. (B) During vasoconstriction, the blood vessels contract, reducing blood flow near the skin.

Describe two factors that can stimulate vasodilation or vasoconstriction.

Figure 12.13 In counter-current heat exchange, heat from blood in an artery is conserved by being transferred to a vein that returns blood to the body’s core. Arterial blood is cooled as it moves from the elbow to the hand, and venous blood is warmed as it moves from the hand up the arm. In warmer conditions, more blood flows back to the core through surface veins. The numbers in the figure indicate the temperature of the blood in degrees Celsius.


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Section 12.1 R E V I E W

Review Questions 1. K/U Explain why an open circulatory system is well

suited to the metabolic needs of an insect. 2. K/U Th e human circulatory system includes the

heart, blood, and blood vessels. Some of the structures involved in the circulation of blood are listed below. In what order does blood entering the heart pass through these structures?

a. pulmonary arteries b. right atrium c. right ventricle d. vena cava

3. C Redesign Figure 12.7 in the form of a cycle chart or other graphic organizer.

4. K/U Identify three key functions of the proteins and the salts in plasma.

5. K/U Explain how the function of the erythrocyte is related to its biconcave shape.

6. A Th e range of the number of red blood cells in men is 4.7 to 6.1 million cells per microlitre (μL) and in women the range is 4.2 to 5.4 million cells/μL. What might be some reasons for this diff erence?

7. A Why is it important for a patient who has a leaky heart valve to have the valve replaced?

8. K/U Identify the fi ve diff erent leukocytes shown in the diagram. State their location in the body, and explain the function of each one.

9. T/I Analyze how the structure of an artery is related to its function.

10. C Draw a diagram to show how your blood returns from your toes to your heart.

11. K/U Summarize some of the basic functions of a mammal’s circulatory system.

12. K/U Explain why plasma is so vital to your existence. 13. K/U Copy the following illustration into your

notebook. Use arrows to show the fl ow of oxygenated and deoxygenated blood. Indicate the source and destination for each of these blood supplies.

14. T/I A pharmaceutical company develops an artifi cial red blood cell that is very eff ective at transporting oxygen but is unable to transport carbon dioxide. Explain what would happen in the blood vessels if this substance were used in a blood transfusion. How would this aff ect the patient? Assume the transfusion has no eff ect on the level of plasma in the blood.

15. T/I In a typical individual, 100 mL of venous blood holds 14 mL of oxygen, and the ventricles each have a volume of 70 mL. Given these data and additional information that you may have to research, how much oxygen does the blood absorb from the lungs in one minute?

16. C Imagine that your teacher has asked you, for extra credit, to make a presentation about the function of diff erent body systems to a class of grade 4 students in your neighbourhood. Use a diagram or a graphic organizer to help you explain the role of the blood and the circulatory system in the following body systems:

a. the digestive system b. the respiratory system

Section Summary• Th e circulatory system transports gases, nutrients, and

wastes throughout the entire body.• Th e three major components of the circulatory system are

the heart, blood vessels, and blood.• Mammals have a closed circulatory system, meaning that

the circulating blood is contained within vessels and kept separate from interstitial fl uid.

• Th e mammalian heart is made up of four chambers—two upper chambers called the atria, and two bottom chambers called the ventricles.

• Th e two main functions of blood are to transport materials throughout the body, and to help maintain a steady body temperature.


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SA noderight atrium

AV node

Purkinje fib es

apex of heart

bundlebranches

right ventricle left ventricle

bundle of His

chordae tendinae

left atrium

SECTION

12.2Monitoring the Human Circulatory System

Key Terms

sinoatrial (SA) node

atrioventricular (AV) node

electrocardiogram (ECG)

blood pressure

systolic pressure

diastolic pressure

sphygmomanometer

cardiac output

stroke volume

Within the heart, a bundle of specialized muscle tissue, called the sinoatrial (SA) node, stimulates the muscle cells to contract and relax rhythmically. Th e SA node is also referred to as the pacemaker, because it sets the pace for cardiac activity. Th e SA node is in the wall of the right atrium. It generates an electrical signal that spreads over the two atria and makes them contract simultaneously. As the atria contract, the signal reaches another node, called the atrioventricular (AV) node, Th e AV node transmits the electrical signal through a bundle of specialized fi bres called the bundle of His. Th ese fi bres relay the signal through two branches of bundles that divide into fast-conducting Purkinje fi bres. Th e Purkinje fi bres initiate the almost simultaneous contraction of all cells of the right and left ventricles, as shown in Figure 12.14.

sinoatrial (SA) node the modified heart cells in the right atrium that spontaneously generate the rhythmic signals that cause the atria to contract

atrioventricular (AV) node the specialized heart cells near the junction of the atria and ventricles that cause the ventricles to contract

The HeartbeatA stethoscope is a medical device used to listen to sounds inside the body (usually from the heart, lungs, or intestines). On one end of the stethoscope is a vibrating membrane, or diaphragm, that is designed to pick up sound. Th e diaphragm is connected to a hollow, air-fi lled tube. Th e doctor holds the stethoscope against the patient’s body, and when the heart beats, small vibrations are picked up and amplifi ed by the diaphragm. Th e sound passes through the tube to the earpieces in the doctor’s ears.

Th e normal heart sound is a repeated double beat, oft en described as “lub-DUB.” Th ese two sounds are made as diff erent heart valves close. Th e fi rst heart sound is the closing of the atrioventricular (AV) valves, as blood is pumped from the atria to the ventricles. Th e second sound is the closing of the semilunar valves, as blood is pumped from the ventricles into the arteries.

Variations in the normal heart sound indicate possible problems. For example, heart murmurs are produced when blood does not fl ow smoothly in the heart. Th is non-smooth fl ow of blood can be caused by stenosis. Stenosis refers to a narrowing in the opening of the heart valves or arteries. A murmur can also occur when a valve closes incompletely, allowing a backfl ow of blood. A murmur that occurs just before the ventricles contract is usually caused by a narrowing in the opening of the AV valves. However, most problems with the heart and valves do not produce an audible murmur. To obtain a better analysis of heart function, doctors measure electrical pulses generated by nerve signals that stimulate contractions of the heart muscles.

Figure 12.14 The SA node sends out an electrical stimulus that causes the atria to contract.


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valve closed

vein

valve open

to heart

vein

valve closed

valve closed

A B

Atrial excitationbegins, atria

contract.

Impulse delayedat AV node,

ventricles fill.

Ventricular excitation inheart apex. Bicuspid

and tricuspid valves close.

Ventricularexcitationcomplete.

Ventricularrelaxation. Semilunar

valves close.

“DUB”“Lub”

ECG:

P TR SQ

SA nodeAV node

Bundlebranches

Purkinje fibres

The Electrocardiogram (ECG)Th e electrical pulses that cause the heart to beat create small voltage changes (only a few milliVolts) that can be measured by electrodes placed on the skin of the chest. Th ese voltage measurements produce an electrocardiogram (ECG) that physicians use to diagnose the health of the heart. Figure 12.15 shows how the waves on an electrocardiogram relate to the beating of the heart.

electrocardiogram (ECG) a record of the electrical impulses generated by a beating heart

Figure 12.16 (A) Small muscles surrounding the veins contract and relax to squeeze blood along the veins. (B) One-way valves inside the veins prevent blood from flowing backward due to the pull of gravity.

Th e fi rst voltage increase, or P wave, labelled on the ECG above as P, begins when the SA node fi res and the atria contract. Th e next spike on the ECG is a cluster of three waves called the QRS complex. It begins when the AV node stimulates the ventricles to contract and the atrioventricular valves close, producing the fi rst heart sound (“lub”). Th e fi nal wave in the cycle is the T wave. It occurs when the ventricles relax and the semilunar valves close to produce the second heart sound (“DUB”). Th e relaxation of the ventricles is followed by the next fi ring of the SA node for the next heartbeat.

Blood PressureAs blood passes through the vessels in the body, it exerts pressure against the vessel walls. Th is is called blood pressure. Changes in blood pressure correspond to the phases of the heartbeat. When the ventricles contract and force blood into the pulmonary arteries and the aorta, the pressure increases in these vessels. Th e maximum pressure during the ventricular contraction is called systolic pressure. Th e phase during which this occurs is called systole. Th e ventricles then relax and the pressure in the pulmonary arteries and the aorta drops. Th e lowest pressure before the ventricles contract is called the diastolic pressure. Th e phase during which this occurs is called diastole.

Two mechanisms in the veins maintain blood fl ow in the proper direction (toward the heart) as blood pressure drops, as shown in Figure 12.16.

blood pressure the force that blood exerts against the walls of blood vessels

systolic pressure the pressure generated in the circulatory system when the ventricles contract and push blood from the heart

diastolic pressure the pressure generated in the circulatory system when the ventricles fill with blood

Figure 12.15 An ECG is produced by placing electrodes on the skin of the chest. The electrodes record voltage changes produced by nerve signals that control the heartbeat. From the information on an ECG, doctors can determine whether a person’s heart is generating signals with a normal frequency, strength, and duration.


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Measuring Blood PressureDoctors commonly measure blood pressure to diagnose the health of the circulatory system. A blood pressure reading shows how much pressure the blood exerts against the vessel walls and indicates the condition of the heart and arteries. Blood pressure is usually measured at an artery in the arm, using a device called a sphygmomanometer [sfi g-mo-meh-NOM-uh-ter], as shown in Figure 12.17. A sphygmomanometer is commonly known as a blood pressure cuff , because it has a cuff that is wrapped around the upper arm and infl ated to exert pressure on a large artery in the arm. Th is temporarily stops the fl ow of blood. As air is slowly let out of the cuff , the blood begins to fl ow again, and the pressure of the blood against the walls of the artery is measured.

sphygmomanometer a medical device used to measure blood pressure

SuggestedInvestigationPlan Your Own Investigation 12-A, Factors Affecting Heart Rate and Blood Pressure

13. How does exercise help reduce high blood pressure? 14. What is stenosis? 15. What is the sinoatrial node and why is it oft en called

the pacemaker of the heart? 16. Predict what a blood pressure reading of 80/120

might indicate.

17. Study the normal ECG pattern shown in Figure 12.15. What eff ect does the increase in voltage at R have on the ventricles of the heart?

18. Identify two causes of high blood pressure. Describe a treatment you could use to lower your blood pressure if it was too high.

Learning Check

Figure 12.17 Using a stethoscope, the doctor or nurse can hear the flow of blood as the pressure in the sphygmomanometer is released and the blood starts to flow again.

When a blood pressure reading is taken, it is recorded in millimetres of mercury, or mmHg (1 mmHg = 0.133 kPa). Th e systolic pressure is presented over the diastolic pressure in the form of a fraction. Th e blood pressure of an average healthy young person is below 120 mmHg over 80 mmHg, or 120/80 (systolic/diastolic). As the heart rate increases, such as during exercise, the ventricles must push a greater volume of blood per unit of time, so the pressure within the arterial system also increases. Although the diastolic blood pressure in a relaxed ventricle drops to almost 0 mmHg during each heartbeat, the blood pressure in the arteries never drops this low, so blood keeps fl owing to the tissues.

Blood pressure is aff ected by genetics, activity, stress, body temperature, diet, and medications. It is normal for your blood pressure to increase when you are exercising and to decrease when you are sleeping. However, continuous high blood pressure, also called hypertension, causes the heart to work harder for extended periods of time. Th is can cause damage to arteries and increases the risk of heart attack, stroke, and kidney failure.


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Cardiac Output and Stroke VolumeTh e amount of blood pumped by the heart is oft en referred to as cardiac output and is measured in mL/min. Cardiac output is an indicator of the level of oxygen delivered to the body. Th erefore, cardiac output is also an indicator of the total level of work the body’s muscles can perform. Two factors contribute to cardiac output: heart rate and stroke volume. Heart rate is the number of heartbeats per minute. Stroke volume is the amount of blood forced out of the heart with each heartbeat. Cardiac output = heart rate × stroke volume.

Stroke volume is determined by two factors. Th e fi rst factor is how easily the heart fi lls with blood. Th is is related to the volume of blood returning to the heart from the veins and the distensibility, or stretchiness, of the ventricles. Th e second factor is how readily the blood is emptied from the heart. Th is is related to the strength of the ventricular contraction and the pressure exerted by the artery walls.

Th e average person has a stroke volume of about 70 mL and a resting heart rate of about 70 beats per minute. Th is means that the cardiac output for a typical adult at rest is 70 × 70, or 4900 mL/minute. Recall that the average adult human has about 5 L of blood in their circulatory system. With a cardiac output of 4900 mL/min, the entire volume of blood in the body passes through the heart about once every minute. With increased physical activity, the cardiac output and rate of circulation increase.

Cardiovascular FitnessA person’s ability to run, swim, play sports, dance, and do any other activity that involves using the muscles depends on their level of cardiovascular fi tness. Cardiovascular fi tness is the capacity of the heart, lungs, and blood vessels to deliver oxygen to working muscle tissues so that they can maintain prolonged physical work. Recall that oxygen is used by the cells to release energy from food molecules.

Table 12.3 compares three hypothetical individuals who have the same cardiac output but diff erent resting heart rates and stroke volumes. Individual A has an average heart rate and stroke volume. Individual B has a higher than average resting heart rate and a lower than average stroke volume. Individual B’s heart beats faster and delivers less blood with each beat than Individual A’s. Individual C is the opposite, with a slow heart rate and a high stroke volume. Th ese factors allow Individual C to maintain the same level of oxygen delivery to the muscles (cardiac output) as both Individual A and Individual B but with less work done by the heart muscles. A low resting heart rate is typical of highly trained athletes and is considered a good indicator of cardiovascular fi tness.

Table 12.3 Comparison of Cardiovascular Fitness and Heart Efficiency in Three Individuals

IndividualResting Heart Rate

(beats/min)Stroke Volume

(mL/beat)Cardiac Output

(mL/min)

A 70 70 4900B 98 50 4900C 35 140 4900

Cardiovascular exercises such as running provide health benefi ts by enlarging the ventricles, increasing their elasticity, and strengthening the ventricle walls. Th ese changes produce an increase in the stroke volume. A good indicator of cardiovascular fi tness is the length of time it takes the heart to recover its resting heart rate aft er strenuous exercise (see Figure 12.18). Th e more fi t the heart is, the shorter the time it takes to return to the resting heart rate.

cardiac output the volume of blood pumped out by the heart in mL/min

stroke volume the volume of blood pumped out of the heart with each heartbeat

Figure 12.18 Doctors sometimes order a cardiac stress test if a person is at risk for heart disease due to high blood pressure, diabetes, or high cholesterol, or if there are other risk factors such as being a smoker or having a family history of heart disease.


S122_BIO11.indd 492 20/05/10 1:44 PM


Review Questions 1. K/U Copy the diagram into your notebook and then

label the SA node, the AV node, branches of the atrioventricular bundle, and the Purkinje fi bres.

2. T/I Predict what might happen if the AV node does not receive a signal from the SA node.

3. A If the gaps between adjacent P waves on an ECG are measured, what can be deduced about the action of the heart?

4. T/I In Table 12.3, how is the fi ttest individual determined? What determines cardiovascular fi tness?

5. K/U What three characteristics of a heartbeat can be determined by examining an ECG?

6. T/I Arrange the following statements in the correct sequence for a heartbeat, beginning with contraction of the atria:

a. atria start to contract b. atria start to fi ll with blood c. AV valves close d. AV valves open e. blood is pumped from atria to ventricles f. blood is pumped from ventricles to artery g. semilunar valves close h. semilunar valves open i. ventricles start to contract j. ventricles start to fi ll with blood

7. K/U Distinguish between systolic and diastolic blood pressure.

8. T/I Th e table below shows the blood pressure readings of a person who did not exercise regularly and ate foods that were high in fat. Construct a graph that shows the blood pressure when the heart is beating and when the heart is relaxed versus age. Interpret the results.

Blood Pressure Readings by Age

Age of Individual

Blood Pressure

when Heart Is Beating

Blood Pressure

when Heart Is Relaxed

Blood Pressure Reading (mmHg)

Type of Pressure

10 120 80 120/80 Normal15 105 70 105/70 Normal20 80 40 80/40 Low25 160 110 160/110 High30 120 78 120/78 Normal35 130 80 130/80 Normal45 140 82 140/82 High60 160 90 160/90 High

9. K/U Th e sounds of the heartbeat include the familiar “lub” and “DUB” sounds. Explain what it is that causes these sounds.

10. K/U Suggest two parts of the body where blood usually loses heat and one part of the body where blood gains heat.

11. A Why does frostbite aff ect the extremities—the nose, ears, fi ngers, and toes?

12. K/U Can an ECG reading provide information about a person’s cardiac output? Explain and give examples.

13. T/I Some people feel dizzy when they stand up aft er a period of lying down. Why do you think this happens?

14. K/U How do you think blood pressure medication lowers high blood pressure?

Section Summary• Th e heartbeat is triggered by an electrical signal

generated by the sinoatrial (SA) node, and transmitted by the atrioventricular (AV) node.

• Doctors use a stethoscope to listen to sounds made by the heart. Variations in the normal heart sound indicate possible problems.

• Blood pressure is measured using a sphygmomanometer, and consists of two diff erent readings—the maximum pressure exerted on the vessel walls is the systolic pressure, and the lowest pressure exerted is the diastolic pressure.

• Cardiac output and stroke volume are used as indicators of cardiovascular fi tness.

• Cardiovascular fi tness is the capacity of the heart, lungs, and blood vessels to deliver oxygen to working muscles during prolonged physical activity.


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A B C

arterial wall

balloon

Closed artery Balloon isreleased

Balloon isinflated

tube containingballoon

balloon

SECTION

12.3Circulatory System Disorders

Key Terms

arteriosclerosis

angioplasty

coronary bypass

aneurysm

arrhythmia

pacemaker

congenital heart defect

ischemic stroke

hemorrhagic stroke

hemophilia

leukemia

nanotechnology

xenotransplant

Smoking, obesity, and insuffi cient exercise are among the risk factors that contribute to cardiovascular disease, which is the leading cause of death among Canadians. In many cases, individuals can reduce or eliminate the eff ects of these risk factors on their lives by making changes to their lifestyle.

ArteriosclerosisArteriosclerosis is a general term that is used to describe several conditions in which the walls of the arteries thicken and lose some of their elastic properties, thus becoming harder. Th e most common type of arteriosclerosis is called atherosclerosis. Th is is a condition in which plaque (fatty deposits, calcium, and fi brous tissues) builds up on the inside of artery walls, as shown in Figure 12.19. As the artery narrows due to this build-up, blood fl ow is decreased and blood pressure is increased. Plaque is especially dangerous if it occurs in arteries that supply the heart, brain, legs, and kidneys. Depending on where the build-up of the plaque occurs, atherosclerosis may lead to angina (chest pain), blood clots, shortness of breath, heart attack, or heart failure. More than 90 percent of heart attacks are caused by atherosclerosis. Healthy lifestyle choices (such as exercise, not smoking, and eating a diet low in saturated fat and high in fruits and vegetables) help to reduce the risk of developing this condition.

Figure 12.19 This ultrasound image shows where blood flow in an artery is normal (red) and slow (green). A build-up of plaque restricts blood flow through the artery.

Figure 12.20 To widen a blood vessel blocked by plaque, surgeons insert a tube with a narrow balloon inside it. The balloon is inflated at the site of blockage to widen the vessel. After the balloon is removed, a permanent tube may be left in place the keep the vessel open.

Treating Arteriosclerosis: AngioplastyOnce arteriosclerosis sets in, several treatment options are available. Medicines such as Aspirin™ prevent platelets from sticking together, thus reducing the formation of clots. Special “clot-busting” medicines such as urokinase and t-PA can be used to break down existing clots and improve blood fl ow. Surgical treatment is also possible. Angioplasty is a procedure in which a surgeon inserts a tube into a clogged artery, as shown in Figure 12.20. When the tube reaches the site where the artery is clogged, a tiny balloon is infl ated to force the artery open. Sometimes, a small permanent wire-mesh tube, called a vascular stent, is inserted into the blocked area during the procedure. Th is stent holds the vessel open and reduces the chance of the blockage redeveloping.

arteriosclerosis general term for several conditions in which the walls of arteries thicken and lose their elasticity

angioplasty a surgical procedure used to open up a clogged artery


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blocked vessels

grafted veins carry arterial blood

Treating Arteriosclerosis: Coronary Bypass Surgeons may choose to re-route the fl ow of blood rather than try to unblock blood vessels. To do this, they take a section of healthy artery or vein from another part of the body, such as the leg, and use it to create a new pathway for blood around the blockage, as shown in Figure 12.21. Th is type of surgery is called a coronary bypass. It may be a double, triple, or quadruple bypass, depending on the number of blockages being bypassed. For example, Figure 12.21 shows a triple bypass.

coronary bypass a surgical procedure in which blood flow is re-routed around blocked arteries

Figure 12.21 A heart after a triple coronary bypass has been performed. Three healthy blood vessels have been attached to create new pathways for the blood to flow between the aorta and three arteries that are blocked.

AneurysmArteries have thick walls that allow them to withstand pressure. However, some medical problems, genetic conditions, and injuries can damage the artery walls. An aneurysm is a bulge in an artery due to a weakened area of the arterial wall (see Figure 12.22). Blood pressure causes the aneurysm to grow larger over time, which gradually increases the risk of it bursting. If the aneurysm bursts, there is internal bleeding that can quickly lead to death. Most aneurysms occur in the aorta, the main artery that goes through the chest and abdomen. Aneurysms are treated by surgery that removes the damaged portion of the blood vessel and replaces it with a patch or graft made of synthetic material such as Dacron® or Tefl on®.

Heart Valve DiseasesAs the heart muscle contracts and relaxes, the valves open and close to allow blood to fl ow into the ventricles and out to the rest of the body. However, there are several conditions that can aff ect the proper functioning of the valves. In some cases, the valve does not close completely and blood fl ows backward instead of forward through the valve. Th is condition is known as regurgitation. In other cases, the valve opening becomes narrowed from thickening or scarring, inhibiting blood fl ow out of the ventricles or atria and causing stenosis.

Heart valve diseases have a variety of causes, including the natural process of ageing, damage from an infection or previous heart attack, and connective tissue disorders. Sometimes, regurgitation and stenosis occur at the same time, and can aff ect more than one valve. Th is reduces the heart’s ability to pump blood through the body, and is a common cause of heart failure.

In cases of regurgitation or stenosis, surgeons may repair valves or replace them. Replacement valves may be taken from animal or human sources, or made from metal, plastic, or other synthetic materials. One of the most common forms of heart valve disease is mitral valve prolapse, in which one or both of the mitral valve (or bicuspid valve) fl aps bulges back into the atrium, preventing the valve from forming a tight seal.

aneurysm a bulge in an artery or heart chamber caused by a weakened area of the heart muscle or arterial wall

Figure 12.22 A coloured MRI scan shows an aneurysm (bulging) in one of the arteries of the neck. The scan was done to determine the cause of the patient’s dizziness.


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ArrhythmiaA problem with the speed or rhythm of the heartbeat is called arrhythmia. An irregular heartbeat may be harmless, but in some cases an abnormal heart rate can lead to insuffi cient blood fl ow to the brain or other organs. Th is condition may be treated with medicines, or may require surgery to implant an artifi cial pacemaker. An artifi cial pacemaker, shown in Figure 12.23, is a small device that emits electrical impulses to control the rate of the heartbeat. It is attached just under the skin of the chest and usually includes a sensor that monitors the heart. Th e pacemaker only transmits an electrical impulse to the heart when the heartbeat is abnormal. Depending on the nature of the problem, the pacemaker may send electrical signals to the atria, or the ventricles, or both.

arrhythmia an irregularity in the speed or rhythm of the heartbeat

pacemaker a device that sends electrical impulses that control the rate of the heartbeat

congenital heart defect a heart defect that is present from birth

Figure 12.23 In a pacemaker, two lead wires with electrodes at their tips send the electrical signals from the pulse generator to the heart muscle. The electrical signals cause the heart muscle to contract, or pump. Most pacemaker implantations are performed under local anesthesia.

Congenital Heart DefectsSome cardiovascular problems are caused by a congenital heart defect, meaning a defect in the heart that has been present since birth. Congenital heart defects include problems in the walls dividing the chambers of the heart, in valves, and in the structure of blood vessels near the heart.

A heart murmur is a relatively common heart defect that involves abnormalities in blood fl ow through the heart, such as one or more of the valves not opening or closing properly. Valve defects can be heard with a stethoscope as a whooshing or rasping sound, which occurs when the blood leaks through the valve. Note that these defects may also arise later in life, in which case they are called acquired heart defects rather than congenital heart defects.

Surgeons can successfully repair or reduce the damage caused by congenital heart defects. Digitizing technology can take data from a CT (computed tomography) scan or MRI scan and create an exact plastic or wax model of a body part, such as a heart. Th is model allows surgeons to plan and even practise the surgery before performing the surgery on the patient. Th e Internet allows surgeons from all over the world to input data and create models for their patients.


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Figure 12.24 A Holter monitor is a portable recording device that continuously monitors heart activity.

StrokeWhen arteries supplying blood to the brain are damaged, cutting off the fl ow of oxygen and nutrients to brain tissue, the result is a stroke. An ischemic stroke [is-KEE-mik strohk] can occur when a clot in a blood vessel blocks the fl ow of blood to the brain. A hemorrhagic stroke [hem-uh-RA-jik strohk] occurs when a blood vessel in the brain bursts and blood fl ows into the surrounding brain tissue. Both types of stroke kill the brain cells in the aff ected area. Th e longer the brain goes without oxygen, the greater the risk of permanent brain damage. Damage from a stroke varies from partial paralysis to death. Death occurs when nerve control to vital organs is aff ected.

Treatment for a stroke must be started within a few hours of symptoms for it to be eff ective. Th ere are three main emergency treatments for stroke—drugs known as clot busters, surgery, and non-surgical procedures. Th e method of treatment depends on the type of stroke, how serious the stroke is, the age and general health of the patient, and how soon treatment is started.

Diagnosing Circulatory System DisordersHow do physicians know the exact location of a clogged blood vessel or an aneurysm? Th ere are several ways to look inside the body at the circulatory system before carrying out any surgery. Coronary angiography, or mapping the coronary arteries, is done by injecting a liquid dye into an artery and then taking X rays as the dye moves through the blood vessels. By mapping the fl ow of dye, a doctor can determine where the circulation is blocked. Th e image in Figure 12.22 on page 495 shows an example of an MRI angiography scan.

Another test used to diagnose heart diseases is an echocardiogram (ECHO), which uses ultrasound technology to create a picture of the heart. Recorded sound waves reveal the shape and movement of the heart valves, the size of the heart chambers, and how well the heart is functioning. An ECHO may be done to determine the cause of a stroke and whether there is any risk of blood clots.

Sometimes doctors order an exercise electrocardiogram, commonly known as a cardiac stress test (which you saw in Figure 12.18 on page 492). An exercise ECG measures the heart’s electrical activity, blood pressure, and heart rate while the person is exercising (usually walking on a treadmill), and helps determine the heart’s response to the stress of exercise. Th is test is usually performed to determine the cause of unexplained chest pain, or whether the person is experiencing irregular heartbeats, excessive dizziness, or fatigue.

When disturbances in the heart rhythm are detected, a patient may be given a small recording device, known as a Holter monitor, to wear over a 24- to 48-hour period. A Holter monitor (see Figure 12.24) is attached to the chest via small electrodes. Th e device records heart rhythm while the person goes about their daily activities, and produces a diagnostic pattern that can later be analyzed by a computer to determine the possible cause of the problem.

Another type of heart monitor, called an event monitor, uses a smaller device, similar in appearance to a wristwatch, that the person activates when symptoms occur. Th is allows the device to record the person’s reading. Th e wearer then phones the reading in to a special monitoring station.

Th e cardiac catheterization technique is usually used in conjunction with other tests, such as angiography. A thin, fl exible tube called a catheter is inserted through an artery in the groin or the arm, and gently guided through the body until the tip reaches the heart. X rays are then taken of the heart and blood vessels. A dye is oft en injected through the catheter to make the heart and blood vessels easier to view.

ischemic stroke a stroke caused by a clot in a blood vessel, blocking blood flow to the brain

hemorrhagic stroke a stroke caused by the bursting of a blood vessel in the brain, which causes blood to leak into the surrounding brain tissue


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A B

Disorders of the BloodA relatively common blood disorder is an inherited, life-threatening condition called hemophilia. Hemophilia is caused by insuffi cient clotting proteins in the blood. As a result, a person with hemophilia bleeds for a long time and is at risk of dying from internal bleeding that may occur as a result of a minor injury. As you learned in Chapter 6, hemophilia is a sex-linked trait in humans. It is a rare disorder that usually occurs only in males. Th e missing clotting protein in the blood is known as factor VIII, and some hemophiliacs can be treated with injections of this substance.

Anemia is a fairly common blood disorder in which the blood contains fewer than normal healthy red blood cells. Anemia can be caused by blood loss, and it can also occur when the red blood cells do not contain enough hemoglobin, which is needed to help carry oxygen from the lungs to the rest of the body’s cells. Th e symptoms of anemia include dizziness, fatigue, shortness of breath, headache, and cold hands and feet. Many types of anemia are mild, short-term, and easily treated with dietary supplements. More severe or chronic anemia can be life-threatening because the lack of oxygen in the blood can damage the brain, heart, and other organs. Th e most severe forms of anemia can cause death.

Leukemia is a cancer of the white blood cells. Th ere are two main types of leukemia: myeloid and lymphoid. Myeloid leukemia is characterized by the presence of too many leukocytes (see Figure 12.25). Th ese leukocytes are immature and unable to fi ght infection. As well, they crowd out the red blood cells, which causes anemia and fatigue. Lymphoid leukemia is a cancer of the lymphocytes, but the symptoms are very similar to those of myeloid leukemia. Both types of leukemia can occur in one of two states: acute or chronic. Th e symptoms of acute leukemia appear suddenly, and death follows quickly. Chronic leukemia may go undetected for months or years.

hemophilia an inherited disorder in which the blood does not clot normally

leukemia cancer of the white blood cells

19. Why is plaque a health risk if it occurs in arteries that supply the brain?

20. Why is it important to treat an aneurysm as soon as it is diagnosed?

21. Aortic stenosis is a condition in which the aortic valve has become narrowed or constricted and does not open and close properly. Describe how this condition aff ects the heart’s ability to pump blood.

22. Describe three procedures used to repair the heart. 23. Explain how a surgeon might distinguish between

the two types of strokes using MRI scans. 24. What is an exercise electrocardiogram, by what

other name is it commonly known, and why might a doctor or other medical professional order such a test for a patient?

Learning Check

Figure 12.25 (A) Normal blood cells. (B) Blood from a patient with leukemia. Notice the increased number of white blood cells (shown in purple).


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Treating LeukemiaTreatment for leukemia includes blood transfusions to increase the number of red blood cells and healthy white blood cells, and chemotherapy. Advances in chemotherapy have vastly improved survival rates, particularly for children. Twenty years ago, children diagnosed with leukemia had less than a 50 percent chance of survival. Th e survival rate is now greater than 85 percent. Another possible treatment is a bone marrow transplant, which provides healthy marrow from which new, healthy white blood cells can grow. (Blood cells are formed in the bone marrow, which is the soft tissue in the large bones in the body.)

Organ TransplantsOn average, more than 1800 Canadians are waiting for an organ transplant at any one time. Th e demand for transplant organs far exceeds the supply, and many people die before a suitable organ becomes available. Th ere are currently over a dozen diff erent types of organs and tissues that can be transplanted from a human donor to a human recipient. Th ese organs and tissues include the lungs, liver, kidney, pancreas, corneas (eye tissues), stomach, heart valves, bone, skin, and the heart (see Figure 12.26).

In this activity you will research and report on the standards and technologies that have been developed in response to the shortage of organs available for transplant.

Materials• reference books• computer with Internet access

Procedure 1. Choose one type of organ transplant that you would like

to research. Using print or on-line resources, research the fi rst successful transplant of that type, and identify some of the important advances in that type of transplant since it was fi rst performed successfully.

2. Create a timeline that shows the developments in standards (criteria) and technologies for the type of organ transplant that you have chosen.

3. Prepare an information sheet in the format of your choice to present your fi ndings to the class.

Questions 1. What are some of the improvements in standards for

organ transplants since the fi rst transplant of the type you chose?

2. Summarize some of the latest technological developments in organ transplantation of that type.

3. What are some of the benefi ts and risks to both the donor and the recipient in any organ transplant?

Activity 12.1 Developments in Organ Transplants

Figure 12.26 A surgeon holds a human heart during a heart transplant operation.


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XenotransplantsTh e activity on the previous page focused on human-to-human organ and tissue transplants, and the shortage of organs available for transplant. One way to increase the supply of organs is to transplant cells, tissues, and organs from other species. A transplant between species is called a xenotransplant, and the transplanted organs are called graft s. Studies of this technique were developed in the 1970s when powerful new drugs were able to reduce the body’s rejection of foreign tissue.

Some animal tissues have been used as graft s to humans for several decades. However, these graft s are chemically treated and are not living, functional tissue. For example, heart valves from pigs have been successfully transplanted into humans to replace damaged heart valves. Prior to the development of synthetic materials such as Dacron® and Gore-tex®, blood vessels from cows were oft en used to replace damaged human blood vessels.

Th ere are many health, safety, legal, ethical, and regulatory issues to consider before xenotransplantation becomes commonplace. Potential problems with xenotransplants, as with transplants from human donors, include the risk of transmitting diseases and the risk of the recipient’s immune system rejecting the tissues. Th ere are still many unanswered questions about how well these techniques might work. Limited clinical trials of xenotransplantation are planned or ongoing in some countries, including Germany, the United States, Spain, and Belgium. Health Canada has begun to look at some of the many issues involved in xenotransplantation, but there have been no clinical trials involving live tissue or organ transplantation to date in Canada.

Artificial HeartsA diff erent way of addressing the demand for donor organs is to develop human-made organs. Faulty human hearts have already been replaced with completely artifi cial, self-contained mechanical pumps, such as the model shown in Figure 12.27. A recent model, made of titanium and plastic, weighs less than 1 kilogram. Th e core mechanism in an artifi cial heart is a hydraulic pump that can pump more than 10 litres of blood per minute. Th e artifi cial heart is powered by a pair of batteries. One battery is external, worn in a belt pack around the person’s waist. It transmits power by wireless energy transfer across the skin to the rechargeable battery inside the person’s abdomen. Th is system allows the person to disconnect the external battery to perform activities such as showering while the internal battery runs the heart. An electronic controller implanted in the abdominal wall monitors and controls the pumping speed of the artifi cial heart.

xenotransplant a transplant of tissues and organs from one species to another

Figure 12.27 This artificial heart is currently used as a temporary replacement for patients awaiting a human heart transplant due to a condition known as biventricular failure.


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cargo(drug)

Closed Open

Figure 12.28 The nanovalve is a microscopic container—only 400 nanometres in diameter—that is easily taken up by cells. The cover remains in place when the body’s internal environment is at a neutral to acidic pH (diagram on the left). In an internal environment with a basic pH, however, the forces holding the structure together are weakened. The cover separates and the drugs inside the container are released (diagram on the right).

Medical Applications of NanotechnologyRecent developments in nanotechnology are helping physicians diagnose cardiovascular and other diseases more quickly and more accurately than was possible in the past. In contrast to the large, expensive, and centralized testing required by scanning machines, nanotechnology involves the use of microscopic structures that are tiny fractions of the width of a human hair.

While conventional diagnostic tools detect disorders in organs and tissues, nanotechnology can detect changes in cells and molecules. Many diseases produce changes in the quantity or types of protein molecules carried in the blood before any obvious symptoms of the disease appear in the body. Molecules that point to the development of a particular disease are called biomarkers. Using nanotechnology, diagnostic kits can give biomarker readings that help diagnose heart disease within 30 minutes from the time a blood sample is taken. Decentralized testing combined with a quick turnaround time for results may lead to earlier detection, more individualized patient care, and reduced costs.

Targeted Drug DeliveryOne of the most common treatments for cancer is chemotherapy—the use of drugs that kill cancer cells. A disadvantage of chemotherapy is that the same drugs also kill healthy cells and produce unpleasant side eff ects. A cancer cell produces diff erent enzymes than the healthy cells surrounding it. Nanotechnology techniques use these enzymes as biomarkers to target delivery of drugs to the cancer cells. Th is results in localized drug therapy that does not touch healthy cells in the surrounding area. Scientists are also testing microscopic containers of drugs, made of biodegradable gels, that can be injected into the body. Th e drugs are released only when they encounter cells that produce certain enzymes.

Figure 12.28 shows a prototype of a nanovalve, a drug-delivery system that is designed to release drugs only to cells that have a basic pH. Th e pH of healthy tissue diff ers slightly from that of diseased tissue. In a chemical environment that is at a neutral to acidic pH, the nanovalve remains closed. Th e nanovalve opens to release the drug when the body’s internal environment is at a basic pH.

nanotechnology technology that uses microscopic structures on the scale of molecules

SuggestedInvestigationInquiry Investigation 12-B, Dissecting a Fetal Pig


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BIOLOGY ConnectionsS T S E

Exploring NanotechnologyImagine that cancer cells could be detected and destroyed one by one, or that a new drug could be tested on a single cell to evaluate its clinical performance. Advances in technologies that allow scientists to focus on individual cells might make these scenarios a reality in the near future. Nanotechnology is the branch of science that deals with development and use of devices on the nanometre scale. A nanometre (nm) is one billionth of a metre (10-9 m). To put this scale into perspective, consider that most human cells are between 10 000 and 20 000 nm in diameter. Nanotechnology is a fast-growing branch of science that will likely leave its mark on everything from electronics to medicine.

ATOMIC FORCE MICROSCOPES At the National Institute of Advanced Industrial Science and Technology in Hyogo, Japan, researchers are using nanotechnology in the form of an atomic force microscope (AFM) to operate on single cells. Th e microscope is actually used as a “nanoneedle.” Th e AFM creates a visual image of a cell using a microscopic sensor that scans the cell. Th en the probe of the AFM, sharpened into a needle tip that is approximately 200 nm in diameter, can be inserted into the cell without damaging the cell membrane. Some scientists envision many applications for this technique. Th e nanoneedle might help scientists study how a cell responds to a new drug or how the chemistry of a diseased cell diff ers from that of a healthy cell. Another application for the nanoneedle might be to insert DNA strands directly into the nucleus of a cell to test new gene therapy techniques that might correct genetic disorders.

LASERS Nanotechnology applications, perhaps in the form of nanosurgery, could be used to investigate how cells work or to destroy individual cancer cells without harming nearby healthy cells. Researchers at Harvard University have developed a laser technique that allows them to manipulate a specifi c component of the cell’s internal parts without causing damage to the cell membrane or other cell structures. Imagine having the capability to perform extremely delicate surgery on a cellular level! In the future, nanotechnology might be our fi rst line of defence to treat cancer. It also might become the standard technique to test new drugs, or even become a favoured treatment used in gene therapy.

This computer-generated image shows a nanobot armed with a biochip. Someday, a biochip, which is an electronic device that contains organic materials, might repair a damaged nerve cell.

biochipnanobot

Connect to Technology

Technologies are ways of solving problems. Besides those problems mentioned here, what are two other problems that nanotechnology applications could solve? Conduct research to discover two recent applications of nanotechnology and share your fi ndings with the class.


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Review Questions 1. K/U Describe what arteriosclerosis is and some of

its possible causes. 2. T/I During angioplasty, plaque is compressed

against the arterial wall. Identify how this surgery might prevent further blocked blood vessels.

3. A Th e hematocrit is the percentage of an individual’s blood that is made up of red blood cells. A small blood sample is placed in a special hematocrit tube. Blood can be separated into its components by putting it into a centrifuge and “spinning it down.” When the centrifuge spins, the red blood cells are forced to the bottom of the tube because they are the heaviest element in the blood. A decreased hematocrit can be the result of a low number of red blood cells, decreased volume of red blood cells, or reduced hemoglobin concentration. Identify one blood disorder that may be indicative of a decreased hematocrit, and list the physical symptoms that are usually associated with this disorder.

4. K/U Describe how a physician might use angiography to diagnose a blockage in circulation.

5. K/U Explain how a pacemaker monitors arrhythmia. 6. T/I Develop a simple test, based on using just a few

drops of a person’s blood, that could determine whether or not that person was anemic. Provide detailed reasoning to support your design.

7. C Briefl y describe how an MRI scan works. 8. A Th ere are two primary types of artifi cial mitral

valves—a mechanical valve and a tissue valve. Mechanical valves are made from metal and pyrolytic carbon, while tissue valves are made from animal tissues. Which valve would a doctor likely recommend to a patient with hemophilia? Explain.

9. K/U Name and describe three diff erent tests that are used to diagnose circulatory system disorders.

10. K/U Suppose you need a heart transplant. Identify two advantages of getting an artifi cial heart transplant, and two disadvantages.

11. C In one form of congenital heart defect, the major blood vessels are transposed. Th at is, the aorta is connected to the right ventricle, and the pulmonary artery is connected to the left ventricle. Th e defect also creates a hole in the septum (the wall that separates the right and left sides of the heart). Draw a diagram to explain how this defect aff ects the fl ow of blood through the heart, and explain the implications for the effi ciency of oxygen delivery in the body.

12. K/U How does an ischemic stroke diff er from a hemorrhagic stroke?

13. A A doctor examines a patient and notes the following symptoms:

• high blood pressure • chest pain • shortness of breath • blood clots What might this person be experiencing, and what is

the treatment? 14. T/I What might be some of the safety or

environmental concerns related to the use of medical nanotechnologies?

15. A What are at least two major problems that a manufacturer would have to overcome to design an artifi cial heart that can work for years inside a patient’s body?

16. T/I Using the library or the Internet, research how lifestyle choices infl uence the development of either hypertension or atherosclerosis. How would improved nutrition aff ect the disorder you researched? How would increased exercise aff ect the disorder? Support your answers with information from your research.

Section Summary• Arteriosclerosis is a general term for a group of

conditions in which the artery walls thicken and lose their elastic properties.

• Th e most common type of arteriosclerosis is atherosclerosis, or the build-up of plaque on the artery walls, which causes over 90 percent of heart attacks.

• Angioplasty and coronary bypass are two common surgical treatments for atherosclerosis.

• Technologies for diagnosing disorders of the circulatory system include chest X rays, angiography, cardiac catheterization, electrocardiogram (ECG), echocardiogram (ECHO), CT scan, and MRI.

• Hemophilia, leukemia, and anemia are three common blood disorders. Th ey are treated in various ways, including blood transfusion.


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12-APlan Your OwnI N V E S T I G AT I O N

Factors Aff ecting Heart Rate and Blood PressureIn this investigation, you will design an experiment to determine how your heart rate and your blood pressure change aft er exposure to diff erent factors, such as physical activity, diff erent foods, and caff einated beverages.

Pre-Lab Questions1. What is the diff erence between heart rate and blood pressure?2. What is the diff erence between systolic and diastolic blood pressure?3. What are some lifestyle choices that may contribute to high blood pressure?

QuestionHow can you isolate factors that aff ect blood pressure and heart rate?

HypothesisMake and record a hypothesis about the eff ects of at least two diff erent factors on heart rate and blood pressure.

Plan and Conduct1. Working in a group, prepare a list of ideas for testing your hypothesis. Make

sure your ideas use only the materials available in your classroom.2. Decide on one idea you can use to design an experiment that can be

conducted in your classroom.3. What will be your independent variable? What will be your dependent

variable(s)? How many trials will you run? Remember that you should test one variable at a time. Plan to collect quantitative data.

4. Outline, step by step, a procedure for your experiment. Assemble the materials you will require.

5. Design a table for collecting your data.6. Obtain your teacher’s approval before starting your experiment.7. Conduct your experiment, and record your results. Prepare a graph or chart

to help you communicate your fi ndings to other groups in the class.

S k i l l C h e c k✓ Initiating and Planning

✓ Performing and Recording

✓ Analyzing and Interpreting

✓ Communicating

Safety Precautions• Do not over-infl ate the blood

pressure cuff .• Students with circulatory or blood

pressure problems should not be test subjects.

Suggested Materials• sphygmomanometer• stopwatch or timer with a digital

display of seconds

Go to Scientifi c Inquiry in Appendix A for help with planning an investigation.


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Analyze and Interpret 1. What were the resting blood pressure and heart rate

measured for each test subject? 2. How did the blood pressure change as a result of the

variable you were testing? How did the heart rate change as a result of the variable you were testing?

3. How long did each change last aft er the test was completed?

Conclude and Communicate 4. Compare your results with the results of other groups

in the class. Explain any diff erences. 5. What is the adaptive advantage of a temporary increase

in blood pressure? What is the adaptive advantage of a temporary increase in heart rate?

Extend Further

6. INQUIRY If possible, obtain two types of blood pressure cuff s. Newer cuff s give digital readings, while older cuff s require the use of a stethoscope to listen to the sounds of blood moving through the vessels. Use both types of cuff to measure a partner’s blood pressure. Compare the readings you got, and describe the diff erences in your experiences with the two cuff s.

7. RESEARCH High blood pressure is a common problem in North America. Fortunately, many diff erent treatments are available. Some examples include treatments used in Western medicine, traditional Aboriginal medicine, traditional Chinese medicine, Ayurvedic medicine, naturopathy, homeopathy, massage therapy, and yoga. Research three treatments for high blood pressure, and prepare a brief report to compare the main features of these treatments. Which treatment would you recommend to someone who has high blood pressure? Justify your choice.

T’ai Chi has been practised in China since ancient times, for the purpose of maintaining health and promoting vitality and a long life.

Yoga is a traditional practice that originated in India. Regular yoga practice promotes physical wellness and mental clarity.

Ayurvedic medicine is an ancient practice originating in South Asia. It aims to balance body, mind, and spirit using a variety of methods.


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InquiryI N V E S T I G AT I O N

Dissecting a Fetal PigNote: Th e illustrations used in this investigation are also available electronically. If you do not dissect a fetal pig or other organism in your course, many virtual dissections are available to enhance your learning.

Pigs are members of the class Mammalia. Before birth, the young are nourished by the placenta in the mother’s womb. For this reason, pigs (like humans) are known as placental mammals. Th e structure and organization of the internal organs of the pig are representative of those of all placental mammals. Although the fetal pig is not yet born, its internal systems are complete. In this investigation you will dissect a fetal pig to study its internal organs. Th is dissection will give you a sense of how internal systems are arranged within your own body.

Dissection involves the careful and systematic examination of the internal structures of an organism. A good dissection will reveal not only the location and structure of individual organs, but also how diff erent organs relate to one another in the various systems of the body. To carry out a successful dissection, you should be familiar with the terms listed in the table below. Th ese are the terms used to describe the location of the various structures of the animal and to direct incisions.

Th is dissection is divided into four parts. In the fi rst part, you will investigate the external anatomy of your specimen and identify its age and sex. In the second part, you will examine the organs of the digestive system. Between each part of the investigation you will store your specimen. Remember to wrap and store your specimen properly, and to label it so you can identify it again.

Anatomical Terms Used to Locate Organs or Incisions During This Dissection

Term Meaning

Dorsal Upper or back surface

Ventral Under or belly surface

Lateral Side

Anterior Toward the front (head) end

Posterior Toward the back end

Superfi cial Near the surface

Proximal Close to

Distal Far from

Pre-Lab Questions 1. Why do you have to wear safety glasses and protective clothing while

conducting this investigation? 2. Why are there safety precautions about working near an open fl ame, and

working in a well-ventilated area, while conducting this investigation? 3. How do you safely dispose of the materials and the dissected specimen?

QuestionWhat are the functional relationships among the digestive, circulatory, and respiratory systems of a mammal?

12-BS k i l l C h e c k

Initiating and Planning

✓ Performing and Recording

✓ Analyzing and Interpreting

✓ Communicating

Safety Precautions

• Extreme care must be taken when using dissecting instruments, particularly scalpels. To the extent possible, make cuts away from your body.

• Th e pigs are preserved in a chemical solution. Wear plastic gloves, eye protection, and an apron at all times, and work in a well-ventilated area.

• If some of the chemical comes into contact with your skin, wash it off . At the end of each lesson, wash your hands thoroughly.

• Dispose of all materials as instructed by your teacher, and clean your work area.

Materials• disposable plastic gloves• preserved fetal pig• string or strong thread• plastic bag with zippered closing

(to store your specimen)• waterproof marker (to identify

your specimen)• newspapers and/or paper towels

(to towel dry your specimen aft er rinsing)

• apron• dissecting tray• dissecting instruments• T pins• large tongs• small syringe or dropper


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ProcedurePart 1: External Anatomy

1. Put on protective clothing and obtain a preserved fetal pig.

2. Rinse your specimen and soak up any excess water from the specimen with newspaper or paper towels. Place your specimen on its side in the dissecting tray.

3. Measure your specimen from the snout to the base of the tail. Use the graph below to estimate the gestational age of your specimen.

26

22

18

14

10

6

2

40 60 80 100 120 140200

Rate of Growth of a Fetal Pig

Gestational age (days)

Leng

th (c

m)

4. Identify the external features of your specimen using the fi gure below. Make your own drawing of the lateral view of your specimen, labelling the features. Record the age of your specimen with your drawing.

nose

tongueankle

anus

head trunk tail

elbow

kneeumbilical cord

shoulder hip

wrist

digit

eyelid

nipples

external ear

5. Turn your specimen onto its back. Using the following two fi gures, determine the sex of your specimen. Examine a specimen of each sex.

6. Make your own drawing of the external reproductive organs of specimens of both sexes. Label the structures.

anus

urogenitalopening

scrotal sac

anusurogenital opening(behind papilla)

genital papilla

Part 2: The Digestive System

A. The Mouth

1. Using a strong pair of dissecting scissors, make a cut in the corner of the mouth, cutting toward the posterior of the specimen. Repeat on the other side.

2. Pry the mouth open. Using the fi gure below, locate and identify the features of the oral cavity.

3. Make your own drawing of the mouth of your specimen, labelling the features.

tongue

epiglottis

soft palate

hard palate

nasopharynx

cut surface

canineincisor


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Analyze and Interpret 1. Explain how the appearance of the following structures

relates to their function as part of the digestive system. Give as much detail as possible, including size, texture, external structure, and internal structure.

a. the teeth b. the tongue c. the epiglottis

2. What diff erences can you see between the pig’s mouth structures and your own? Suggest a reason for these diff erences.

B. Exposing the Abdominal Organs

1. Place the pig in the dissecting tray with its ventral surface uppermost. Spread out the limbs. Tie a piece of string to one of the forelimbs near the ankle. Pass the string under the tray and securely tie the other forelimb. Repeat the process with the hind limbs.

2. Select a point just anterior to the umbilical cord on the specimen’s ventral surface. Using forceps, pinch the skin of the abdomen along the midventral line and pull it slightly away from the animal. With your scissors, make an incision in the skin. Th e incision should be just large enough to pass the point of your scissors through. Now make a midventral cut ending just posterior to the midline of the animal (shown as #1 in the top fi gure). To avoid damaging the organs as you cut, keep the tips of the scissors pointing up. Be careful not to damage the umbilical cord.

3. From the same starting point, make a second incision around the base of the umbilical cord extending back to just anterior to the anus (shown as #2 on the top fi gure). You may wish to turn your specimen around so you can cut away from you. Repeat on the other side.

4. Locate the base of the sternum (breast bone), situated in the centre of the chest. Th e ribs are attached to the sternum. Select a point slightly posterior to the sternum and cut across the ventral surface (shown as #3 in the top fi gure). Th e incision should be posterior to the diaphragm, which you will be able to see as a dome-shaped layer of muscle separating the abdominal and thoracic cavities.

5. Make two fi nal horizontal incisions, one on each side of the #2 cuts, bordering the umbilical cord and just anterior to the hind limbs (shown as #4 in the top fi gure). Use T pins to pin back the skin to expose the internal organs of the abdominal cavity. Th e T pins should point away from the specimen so they will not interfere with your work.

6. Th e organs of the abdomen are covered and protected by a membrane called the peritoneum. Th e double-layered sheets of peritoneum are called mesenteries. Using forceps or a dissecting probe, gently move the mesenteries aside to reveal the underlying organs.

nostril

eye

external ear

elbow

ankle

knee

wrist

digit

umbilical cord

tail

anus

2 2

3

1

44

7. Using the fi gure below and the photo on the next page, locate and identify the organs of the abdominal cavity. Make a drawing of your specimen showing the location of the internal organs and labelling them.

urinary bladder

umbilical artery

umbilical cord

umbilical vein

right lobe of liver

small intestine

pancreasstomach

spleen


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C. Examining the Abdominal Organs

1. Locate the liver, the largest organ of the abdominal cavity. Describe its appearance in your own words. Note its diff erent lobes.

2. Locate and describe the esophagus. Note how it passes through the diaphragm just before it enters the stomach.

3. Locate and describe the stomach. Carefully cut open the stomach and describe the inner surface.

4. Locate and describe the pancreas, situated below the stomach, between the stomach and the small intestine. It is usually lighter in colour than the surrounding organs.

5. Locate and describe the small intestine. See if you can identify the separate portions of the duodenum, ileum, and jejunum.

6. Using forceps or a probe, gently lift the connective tissue that links the liver and the duodenum. Locate the bile duct in this mesentery and trace it back to its source at the gall bladder. Th e gall bladder is embedded on the surface of the liver.

7. Move to the distal end of the small intestine and locate the point on the left side of the abdominal cavity where the large intestine begins.

8. Th e main part of the large intestine is called the colon. Identify the path the colon takes in the abdomen.

9. Toward the end of the large intestine is the rectum. Note where the tract terminates at the anus.

10. Cut the esophagus as close to the top of the abdominal cavity as you can. Make a second cut as close as you can to the end of the digestive tract near the anus. Carefully remove the entire digestive tract, in one piece, from the specimen.

11. Carefully cut away the connective tissue around the digestive tract. Unravel the tract and make a drawing of it, identifying the diff erent sections of the digestive tract. Measure each section of the digestive tract.

12. Make a drawing of the unravelled digestive tract and describe the appearance of this tissue in your own words.

liver

heart

stomach

umbilical arteries

right carotidartery

right lung

diaphragmliver

largeintestine

umbilical cord

small intestine

urinary bladder

larynx

thyroidgland

left carotidartery

heart

left lung

umbilical vein

stomach


relates to their function as part of the digestive system. Give as much detail as possible, including size, texture, external structure, and internal structure.

a. liver b. pancreas c. esophagus d. stomach e. small intestine f. large intestine g. gall bladder

4. Using your own drawings of the abdominal organs, trace the path of food from the mouth to the rectum. Identify the major steps in the digestive process that take place along the way.


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Part 3: The Circulatory System

A. Exposing the Organs of the Thoracic Cavity

1. Locate the base of the sternum (breast bone), which is in the centre of the chest. Th e ribs are attached to the sternum. Use this as the starting point for your incision. With forceps, pinch the skin of the abdomen along the midventral line and draw it slightly away from the animal. With your scissors, make an incision in the skin—the incision should be just large enough to pass the point of your scissors through. Now make a midventral cut (shown as #1 in the fi gure below). Th is cut should extend as far forward as the hairs near the base of the throat. Be careful not to damage the underlying body wall as you cut. Remember to keep the tips of your scissors pointing up, not down, to avoid damaging the internal organs.

2. Next, make two cuts (shown as cuts #2 and #3 in the fi gure below) from the midventral line in the region of the thoracic cavity. Carefully lift the skin and pin it to the sides of the specimen using T pins. Th e T pins should point away from the specimen so they will not interfere with your work.

nostril

eye

external ear

elbow

ankle

knee

wrist

digit

umbilical cord

tail

anus

1

2

3

3. Using a sturdy pair of dissecting scissors, cut the ribs along the sternum, and pry them apart to reveal the organs of the thoracic cavity.

4. Using forceps or a dissecting probe, remove the connective tissues and membranes that surround the lungs and heart.

5. Using the diagram below and the photo on page 509, identify the internal organs of the thoracic cavity. Make a drawing of your specimen.

right atrium

thymus gland

ribs (cut)

diaphragm

left lungright lung

right ventricleleft ventricle

left atrium

pulmonary artery

thyroid gland

larynx

B. Examining the Organs of the Circulatory System

1. Using the previous fi gure and the bottom fi gure on the next page for reference, identify and compare the sizes of the following major blood vessels.

a. aorta b. superior vena cava c. pulmonary artery d. pulmonary vein e. inferior vena cava

2. Your specimen may have a small blood vessel connecting the pulmonary artery to the aorta. Th is vessel is called the ductus arteriosis. Try to locate this vessel on your own specimen. If you cannot fi nd it, examine another specimen in which this vessel is visible.

3. Locate and describe the heart. 4. Make a drawing of your specimen showing the location

of the circulatory organs. 5. Carefully cut through the blood vessels a short distance

from the heart. Make an incision in the ventral surface of the heart as shown in the top fi gure on the next page. Your incision should expose all four chambers of the heart.

6. Using the bottom fi gure on the next page for reference, identify the internal features of the heart. Try to locate and identify the heart valves at the opening to the blood vessels.


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7. Compare the structure of the diff erent chambers of the heart. Make a labelled drawing and describe the structures in your own words.

right atrium

right ventricle left ventricle

left atrium

aorta


relates to their function as part of the circulatory system. Give as much detail as possible, including size, texture, external structure, and internal structure.

a. right atrium e. arteries b. left atrium f. veins c. right ventricle g. ductus arteriosis d. left ventricle h. heart valves

right pulmonaryarteries

right atrium

atrioventricular(tricuspid) valve

right ventricle

inferior vena cava

right pulmonary veins

superior vena cavaleft common carotid artery

semilunarvalves

left pulmonaryveins

aorta left pulmonaryarteries

pulmonary trunk

left atrium

atrioventricular(mitral) valve

left ventricle

septum

Part 4: The Respiratory System

Examining the Respiratory Organs

1. Using the top fi gure on page 510 for reference, identify the major organs of the respiratory system.

2. Note the diff erence in structure between the right and left lung. In your own words, describe the structure and texture of the lungs.

3. Locate and describe the pleural membranes encasing each lung.

4. Using a probe, move aside the layers of muscle to work deeper into the neck. If necessary, carefully cut the muscle tissue. Locate the larynx, trachea, and esophagus. Describe the diff erence in structure between the trachea and esophagus.

5. Examine the rib cage and try to identify the external and internal intercostal muscles.

6. Open the mouth and describe the relationship between the glottis, esophagus, and pharynx.

7. Trace the passage of the trachea through the throat. Try to identify the two branches of the bronchi.

8. Make a drawing of your specimen showing the location of the organs of the respiratory system.

9. Using a small syringe or dropper, push a small amount of air into the trachea. Note the infl ation of the lungs.


relates to their function as part of the respiratory system. Give as much detail as possible, including size, texture, external structure, and internal structure.

a. trachea e. larynx b. right lung f. glottis c. left lung g. diaphragm d. pleural membrane h. rib cage

7. Using your own drawings, trace the path of air from the mouth to the lungs.

Conclude and Communicate 8. In what ways was your understanding of the digestive,

circulatory, and respiratory systems enhanced by your observation of the real organs?

9. Identify one way in which the respiratory system and the circulatory system work together.

10. Identify one way in which the circulatory system and the digestive system work together.

Extend Further

11. INQUIRY Based on your study of the heart, write a question that could be answered by examining the heart structures.

12. RESEARCH Use the Internet or other resources to research a disorder of the heart that is related to improper functioning of the heart valves. What causes this condition? How can it be treated?


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SUMMARYChapter 12

The Function of CirculationSection 12.1

The circulatory system is a transportation and internal regulation system that is vital to the functions of all other body systems.

KEY TERMSaortaatrioventricular valvebloodblood vesselcardiac circulationcirculatory systemclosed circulatory systemheart

open circulatory systempulmonary arterypulmonary circulationpulmonary veinsemilunar valvesystemic circulationvasoconstrictionvasodilation

KEY CONCEPTS• The circulatory system transports gases, nutrients, and

wastes throughout the entire body.

• The three major components of the circulatory system are the heart, blood vessels, and blood.

• Mammals have a closed circulatory system, meaning that circulating blood is contained within vessels and kept separate from interstitial fl uid.

• The mammalian heart is made up of four chambers—two upper chambers called the atria, and two bottom chambers called the ventricles.

• The two main functions of blood are to transport materials throughout the body, and to help maintain a steady body temperature.

Monitoring the Human Circulatory SystemSection 12.2

The stethoscope, the sphygmomanometer, and other non-invasive technologies help doctors to monitor the health of the human circulatory system.

KEY TERMSatrioventricular (AV) nodeblood pressurecardiac outputdiastolic pressureelectrocardiogram (ECG)

sinoatrial (SA) nodesphygmomanometerstroke volumesystolic pressure

KEY CONCEPTS• The heartbeat is triggered by an electrical signal generated

by the sinoatrial (SA) node, and transmitted by the atrioventricular (AV) node.

• Doctors use a stethoscope to listen to sounds made by the heart. Variations in the normal heart sound indicate possible problems.

• Blood pressure is measured using a sphygmomanometer, and consists of two diff erent readings—the maximum pressure exerted on the vessel walls is the systolic pressure, and the lowest pressure exerted is the diastolic pressure.

• Cardiac output and stroke volume are used as indicators of cardiovascular fi tness.

• Cardiovascular fi tness is the capacity of the heart, lungs, and blood vessels to deliver oxygen to working muscles during prolonged physical activity.

Circulatory System DisordersSection 12.3

Technological advances give doctors many non-invasive and minimally invasive technologies to diagnose and treat disorders of the circulatory system.

KEY TERMSaneurysmangioplastyarrhythmiaarteriosclerosiscongenital heart defectcoronary bypasshemophilia

hemorrhagic strokeischemic strokeleukemiananotechnologypacemakerxenotransplant

KEY CONCEPTS• Arteriosclerosis is a general term for a group of conditions

in which the artery walls thicken and lose their elastic properties.

• The most common type of arteriosclerosis is atherosclerosis, or the build-up of plaque on the artery walls, which causes over 90 percent of heart attacks.

• Angioplasty and coronary bypass are two common surgical treatments for atherosclerosis.

• Technologies for diagnosing disorders of the circulatory system include chest X rays, angiography, cardiac catheterization, electrocardiogram (ECG), echocardiogram (ECHO), CT scan, and MRI.

• Hemophilia, leukemia, and anemia are three common blood disorders. They are treated in various ways, including blood transfusion.


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REVIEWChapter 12

Knowledge and Understanding1. Which of the following occurs during diastole?

a. Th e atria fi ll with blood.b. Blood fl ows into the ventricles.c. Th e elastic recoil of the arteries maintains blood

pressure.d. Th e semilunar valves are closed but the AV valves

are open.e. All of the above are correct.

2. An AV valve prevents backfl ow of blood froma. the right ventricle into the right atriumb. the left atrium into the left ventriclec. the aorta into the left ventricled. the pulmonary vein into the right atriume. the pulmonary artery into the left atrium

3. Which structure initiates a heartbeat?a. AV nodeb. right atriumc. SA noded. left ventriclee. right ventricle

4. What is fi brinogen?a. a blood protein that is carried by fatsb. a cell fragment involved in the blood clotting

mechanismc. a blood protein that is converted to fi brin to form a

blood clotd. a leukocyte that is involved in trapping bacteria and

virusese. a lymphocyte that regulates osmosis in tissues

5. What causes the semilunar valves to close?a. contraction of the ventriclesb. contraction of the atriac. stimulation of the SA noded. backfl ow of blood in the aorta and pulmonary

artery during diastolee. contraction of the cardiac muscle that makes up

the valves6. Which structure prevents the backfl ow of blood from

the ventricles to the atria?a. valveb. septumc. sinoatrial noded. atrioventricular nodee. superior vena cava

7. Human beings have a double circulatory system that includes pulmonary circulation and systemic circulation. Complete the following statement by choosing the correct pair of terms below.

During systemic circulation, blood is carried away from the heart. During pulmonary circulation, blood is carried away from the heart.

a. oxygenated; deoxygenated b. deoxygenated; deoxygenated c. oxygenated; oxygenated d. deoxygenated; oxygenated e. oxygenated; detoxifi ed

8. Th e muscles of the heart contract and relax rhythmically. An electrical signal from a special bundle of tissue is actually responsible for setting the pace for the cardiac contractions. What is this tissue called?

a. AV node b. SA node c. Purkinje fi bres d. bundle of His e. apex

9. You are told that your blood pressure is 108/72. What does the 72 refer to?

10. Use a graphic organizer such as a Venn diagram to show three similarities and two diff erences between open and closed circulatory systems.

11. Copy the following diagram in your notebook and add the following labels: P wave, T wave, QRS complex, “lub” and “DUB”.

12. Use a graphic organizer or a table to identify at least three circulatory disorders, and describe the diagnostic technologies associated with them.

13. How is the hemolymph of an open circulatory system moved throughout the body?

14. What is an open circulatory system and what is an example of this mechanism?

15. Make a table to compare and contrast pulmonary and systemic circulation.

16. What disorder is angioplasty used to treat? Describe the steps involved in this procedure.


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REVIEWChapter 12

Thinking and Investigation 17. Why is it considered important for healthy people to

donate blood on a regular basis? 18. A person’s blood pressure is measured before and aft er

exercise. What eff ect would you expect the exercise to have on the systolic blood pressure and on the diastolic blood pressure? Explain.

19. Copy and complete the following chart.

Heart Activity During One Heartbeat

Part of Heartbeat

Diastole Begins

Diastole Is Complete

Systole Begins

Systole Is Complete

Are the AV valves open or closed?Are the semilunar valves open or closed?Are the atria relaxed or contracted?Are the ventricles relaxed or contracted?Where is the highest pressure during this phase?

20. Predict what would happen in an ECG if arrhythmia or a conduction failure at the AV node occurs. Use a drawing to illustrate your answer.

21. Explain why hypertension can have the negative health eff ects that it has.

22. Th e diagram below shows a blood sample from a healthy patient. Use the diagram to answer the questions that appear at the top of the right column.

a. What device was likely used to prepare this sample? b. Identify each layer in the sample and estimate the

percentage of blood volume in each layer. c. You are given a similar sample, prepared in the

same way, for a patient suspected of suff ering from anemia. Predict how the relative volume of each layer in this sample might compare to the sample from the healthy patient.

d. What information or assumptions did you use to make a prediction in part (c)?

23. Interpret the information in the table below and answer the questions that follow.

Blood Cell Counts for Six Individuals

PersonRed Blood Cell

Count (cells/mcL)White Blood cell

Count (cells/mcL)

A 7 300 000B 5 000 000C 3 200 000D 8 000E 17 300F 6 300

Note: Blood cell counts are usually expressed in units of cells/mcL rather than cells/μL. Both of these mean “cells per microlitre.”

a. Which person has the normal number of red blood cells? of white blood cells?

b. Which person has symptoms of anemia? c. Which person has symptoms of leukemia?

24. Make a drawing that you could use to explain to a grade 1 class why regular exercise is good for the heart.

Communication 25. Using a format of your choice, summarize the

technologies that have improved our understanding of the human heart and how it functions.

26. Correct the following false statements: a. Th e semilunar valves separate the atria from the

ventricles. b. Th e aorta is the main artery of the heart, taking

deoxygenated blood to the other body systems. c. In counter-current exchange, double circulation

keeps oxygenated and deoxygenated blood separate. d. All veins carry oxygen-poor blood and all arteries

carry oxygen-rich blood. e. Fibrinogen is a cell fragment involved in the blood

clotting mechanism.


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27. List some common disorders associated with the cardiovascular system.

28. Elite endurance trained athletes (such as marathon runners and cross-country skiers) have resting heart rates as low as 30 beats per minute, and have a maximum cardiac output of 40 000 mL/min. Compare these data to the cardiac output of an average individual and infer why the huge diff erence might exist.

29. Design a poster, brochure, or presentation to promote awareness of how we can maintain a healthy heart.

30. Research the possible consequences of quadruple bypass surgery. Create a cause-and-eff ect map to summarize your fi ndings.

31. Some people increase their risk of a stroke by eating a poor diet, smoking, and getting little or no exercise. Develop a plan to educate people about maintaining a healthy lifestyle. How might a healthy lifestyle contribute to a healthy circulatory system?

32. Human beings have a four-chambered heart, which is divided into two upper atria and two lower ventricles. Two veins, the superior vena cava and the inferior vena cava, empty blood to the right atrium of the heart. Th e right side of the heart is involved in pulmonary circulation and the left side of the heart is involved in systemic circulation.

a. Describe the main functions of the circulatory system.

b. How is the superior vena cava functionally diff erent from the inferior vena cava?

c. Why is it important for a person who has a leaky heart valve to have the valve replaced?

33. Summarize your learning in this chapter using a graphic organizer. To help you, the Chapter 12 Summary lists the Key Terms and Key Concepts. Go to Using Graphic Organizers in Appendix A to help your decide which graphic organizer to use.

Application 34. Research how you would use a stethoscope to

determine whether each of the following had occurred. Include details of what you would expect to fi nd in each case.

a. damage to the mitral valve b. damage to the tricuspid valve c. damage to the aortic valve d. damage to the pulmonary valve e. damage to the AV node

35. Use a fl owchart or any other graphic organizer to illustrate how the “lub” and “DUB” sounds of the heart are created.

36. You are sitting in a hot tub aft er a day of strenuous outdoor activity. Infer what is happening to your circulatory system.

37. Research fi ve common misconceptions that people have about donating blood and present your fi ndings to the class.

38. Dizziness can occur when a person stands up quickly, even if the person is in excellent physical shape. Explain how this healthy person might feel dizzy, in terms of stroke volume and heart rate.

39. A baby is born with a septal defect (a hole in the septum separating the right and left ventricles), as shown in the fi rst diagram below. Compare this to the heart of a frog, shown in the second diagram, and answer the questions that follow.

left ventricle

Heart with a septal defect

blood fromlungs

left atrium

blood to lungs

rightventricle

right atrium

blood frombody

ventricularseptal defect

blood frombody

oxygen-richblood

artery

oxygen-poorblood

oxygen-rich blood

vein from lungs

left atrium

right atrium

vein from body

ventricle

Heart of a frog

a. In what ways are the two hearts similar? b. What are the implications of this defect for the

baby? Do these implications apply to the frog as well? Why or why not?

40. Iron defi ciency, or anemia, oft en results in fatigue and pallor. Explain how these symptoms could result from inadequate iron in the diet or other factors such as diseases or exposure to pollutants.


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Chapter 12 SELF-ASSESSMENT

Select the letter of the best answer below. 1. K/U Arteries carry blood away from the heart and

veins carry blood toward the heart. Which of the following pairs of terms matches the blood vessel with the type of blood it carries?

a. superior vena cava, oxygenated blood b. pulmonary vein, oxygenated blood c. pulmonary artery, oxygenated blood d. inferior vena cava, oxygenated blood e. aorta, deoxygenated blood

2. K/U Blood is a circulating tissue that consists of diff erent types of cells—white blood cells, red blood cells, and platelets—suspended in a fl uid called plasma. Complete the following statement by choosing the correct pair of terms below.Red blood cells diff er from most other cells in the body in that they contain and they lack .

a. a cell membrane; a nucleus b. a nucleus; hemoglobin c. a nucleus; a cell membrane d. a cell membrane; hemoglobin e. hemoglobin; a nucleus

3. K/U Th e SA (sinoatrial) node stimulates the muscles of the heart and is responsible for their rhythmical contraction and relaxation. Th e SA node of the heart is located in the wall of the

a. left ventricle c. left atrium b. right ventricle d. right atrium e. inferior vena cava

4. K/U In human beings, the heart is located on the left side in the chest between the two lungs. Complete the following statement by choosing the correct pair of terms below. Th e human heart, like that of other mammals, has

chambers. Th e top two chambers are called .

a. three; atria b. four; septa c. three; ventricles d. four; atria e. two; ventricles

5. K/U Which of these is a factor that causes blood pressure to increase?

a. vasoconstriction b. vasodilation c. an increase in urine output d. a decrease in body fl uid volume e. decreased body temperature

6. K/U Which statement summarizes the function of the pulmonary circuit (the path of pulmonary circulation)?

a. transports O2 through the heart, lungs, and body tissues

b. transports O2 and nutrients to the body tissues c. fi lters waste products from the blood d. transports CO2 to the lungs and picks up O2 from

the lungs e. fi lters toxins from the blood

7. K/U Th e “lub,” or fi rst heart sound, is produced by the closing of

a. the aortic semilunar valve b. the pulmonary semilunar valve c. the tricuspid valve d. the bicuspid valve e. both AV valves

8. K/U Anemia can result from a. an iron-rich diet b. an increase in red blood cell count c. lack of hemoglobin production d. reduced blood pressure e. reduced number of leukocytes

9. K/U Which condition would a stent be most likely used to treat?

a. hemophilia b. atherosclerosis c. mitral valve prolapse d. hypertension e. arrhythmia

10. K/U Which of the following is a type of cancer of the white blood cells?

a. leukemia b. anemia c. hemophilia d. ischemic stroke e. stenosis


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Self-Check

If you missed question... 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Review section(s)... 12.1 12.1 12.2 12.1 12.2 12.1 12.2 12.3 12.3 12.3 12.2 12.3 12.1 12.3 12.1 12.1 12.3 12.1 12.2 12.2 12.2 12.3 12.3 12.2 12.3

Use sentences and diagrams as appropriate to answer the questions below.11. A Assume your heart rate is 70 beats per minute

(bpm), and your stroke volume is 75 mL/beat.a. Calculate your cardiac output.b. In one year, what volume of blood does your heart

pump? Express your answer in litres.12. A Are there alternatives to human blood for a

transfusion? Explain.13. C Draw a simple diagram of the human

circulatory system showing the fl ow of blood from the heart through all major parts of the body.

14. T/I If the right ventricle is not able to pump blood properly, what eff ect does this have on the lungs?

15. T/I A penguin’s body is well protected from the cold by thick down and blubber, but its feet have no insulation. Explain how it is possible that a penguin does not lose heat through its feet.

16. T/I What information can be gained by checking the numbers and types of cells present in the blood of a person who is sick?

17. T/I Leeches are bloodsucking aquatic animals that are sometimes used to treat conditions involving poor blood supply to various tissues. Why do you think this might be a useful treatment when reattaching a fi nger?

18. K/U Referring to the diagram below, identify the four main valves that help maintain blood pressure and that keep the blood fl owing in one direction. Describe how they are able to perform these functions.

19. A Examine the following abnormal ECG patterns. a. What type of problem do you think each patient

may have? b. What type of device can be implanted in a patient’s

heart to correct some abnormalities of the heart, and how does it generally work?

A

B

20. T/I Why would an exercise electrocardiogram (stress test) be conducted on an individual rather than just a seated ECG?

21. A Cardiac output remains relatively constant, even during exercise. If the heart rate is above 200 beats per minute, however, the cardiac output can begin to decrease. How does a heart rate of 200 beats per minute aff ect the duration of heart relaxation? How does this aff ect the stroke volume?

22. K/U Describe three possible treatments for a blocked coronary artery.

23. T/I Veins have small valves known as leafl et valves that prevent blood from fl owing backward. If these valves become weak or damaged, blood backs up and pools in the veins, causing the veins to become swollen and twisted. Th is condition is known as varicose veins. Research some of the likely causes of varicose veins and some possible treatments.

24. T/I If a pacemaker received faulty signals from the heart, what would happen?

25. A Why should people with hypertension reduce their salt intake?


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chapter 12 the circulatory system - tdchristian...

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