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Circulation-body’s transport system

Chapter 16

Section 1

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Key Concepts

What are the functions of the cardiovascular system?

What is the function and structure of the heart?

What path does blood take through the cardiovascular system?

What are the functions and structures of arteries, capillaries, and veins?

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Key terms

Cardiovascular system Heart

Atrium Pacemaker

Ventricle Valve

Artery Capillary

Vein Aorta

Coronary artery Pulse

Diffusion Blood pressure

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The Cardiovascular System

Like the roads that link all parts of the country your body has a “highway” network-the cardiovascular system.

The cardiovascular system carries needed substances to cells and carries waste products away from cells. In addition, blood contains cells that fight disease.

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Delivering Needed Materials

Blood carries needed substances by the body from one part to another Ex. Oxygen from your lungs to other body

cells Ex. Glucose is transported to cells to produce

energy

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Removing waste products

Cardiovascular system picks up wastes from cells Ex. Cells break down glucose, and produce

carbon dioxide as a waste product Carbon dioxide passes from the cells into the

blood Cardiovascular system then carries carbon

dioxide to the lungs where it is exhaled

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Fighting Disease

Transports cells that attack disease-causing microorganisms

Blood cells will kill the microorganisms and help you get well

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Heart

Without the heart could blood flow anywhere?

Each time the heart beats, it pushes blood through the blood vessels of the cardiovascular system.

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Size and Location

You heart is about the size of your fist It is located in the center of your chest The heart lies behind the sternum and

inside the rib cage It is made of cardiac muscle-Does the

cardiac muscle get tired?

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Heart Structure

Heart has a right and a left side Right and left sides are separated by a wall of

tissue called the septum Each side has an upper and lower chamber

Upper chamber-atrium (plural – atria) Lower chamber-ventricle A pacemaker is located in the right atrium to send out

signals that make the heart muscle contract

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Atrium

Receives blood that comes into the heart

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Ventricle

Pumps blood out of the heart

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Atria/Ventricle

Atria and ventricles are separated by valves

This valve is a flap of tissue that prevents blood from flowing backward

Valves are also located between the ventricles and the large blood vessels that carry blood away from the heart

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How the heart works

Phase one-heart muscle relaxes and heart fills with blood

Other phase-heart muscle contracts and pumps blood forward

When the heart muscle relaxes blood flows into the chambers

Atria contract squeezing blood out of the atria through the valves and into the ventricles

Ventricles then contract

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(2)

Contraction closes the valves between the atria and ventricles making the lub sound and squeezing blood into large blood vessels

As valves between ventricles and blood vessels snap shut they make the dup sound

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Two Loops

Body has three kinds of vessels Arteries-carry blood away from heart Capillaries-substances are exchanged

between the blood and body cells Veins-carry blood back to the heart

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(2)

Blood flow is like a figure eight with the heart at the center of the two loops

Loop one-blood travels from the heart to the lungs and back to the heart

Loop two-blood is pumped from the heart throughout the body and then returns again to the heart

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(3)

Right side of heart pumps to lungs Left side to the rest of the body Blood travels in one direction, and takes

less than a minute to travel through your body

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Loop one

To the lungs and back Blood that flows into the right atrium contains little

oxygen and a lot of carbon dioxide This is oxygen POOR blood-it is DARK RED Blood then flows from the right atrium into the

right ventricle The ventricle pumps the oxygen poor blood into

the arteries that lead to the lungs As blood flows through the lungs, large blood

vessels branch into smaller ones

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Loop Two-to the body and back

Second loop begins as the left atrium fills with oxygen rich blood coming from the lungs

Blood then moves into the left ventricle from the left ventricle blood is pumped into the aorta-the largest artery in the body

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(2) After passing through branching arteries, blood

flows through tiny capillaries in different parts of your body, such as your brain, liver and legs

These vessels are in close contact with body cells Oxygen moves out of the blood and into the body

cells, at the same time, carbon dioxide passes from the body cells into the blood

Blood which is low in oxygen then flows back to the right atrium of the heart through veins, completing the second lap

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Arteries When blood leaves the heart it travels through

arteries Right ventricle pumps blood into the arteries that go

to the lungs Left ventricle pumps blood into the aorta Smaller arteries branch off the aorta First branches are called coronary arteries and

carry blood to the heart itself Other branches carry blood to the brain, intestines

and other organs, each artery branches into smaller and smaller arteries

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Artery structure

Walls of arteries are generally very thick they consist of three cell layers Innermost layer-made up of epithelial cells and is

smooth Smooth surface enables blood to flow freely Middle layer-mostly muscle tissue Outer wall-flexible connective tissue They are both strong and flexible Arteries are able to withstand the enormous pressure

of blood as it is pumped by the heart and to expand and relax between heart beats

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Pulse

The alternating expansion and relaxation of the artery wall

Every time the heart’s ventricles contract they send a spurt of blood out through all the arteries in your body

This spurt travels It pushes the artery walls and makes them expand,

after the spurt passes they relax and become narrower again

Heartbeats are then number of times an artery pulses beneath your fingers

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(2) Eventually blood flows through tiny capillaries that

are in close contact with the air that comes into the lungs

Air in the lungs has more oxygen than the blood in the capillaries, oxygen moves from the lungs into the blood

Carbon dioxide moves in the opposite direction-from the blood into the lungs

As the blood leaves the lungs it is now rich in oxygen and poor in carbon dioxide

Blood is bright red and flows to the left side of the hear and will be pumped through the second loop

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Regulating Blood Flow The layer of muscle in an artery acts as a control

gate When the muscle contracts the opening in the artery

becomes smaller When the muscle relaxes the opening becomes

larger Ex. You eat, your stomach and intestines need a greater

blood supply for digestion. More blood flows through them In contrast when running your stomach and intestines

need less blood than the muscles in your legs arteries leading to the digestive organs become narrower-decreasing blood flow

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Capillaries

Materials are exchanged between the blood and the body’s cells

Capillary walls are only one cell thick, allowing materials to pass easily through them. Oxygen and glucose pass from the blood through the capillary walls to the cells. Waste products travel in the opposite direction-from cells through the capillary walls into the blood

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(2)

Materials are exchanged between blood and the body cells by diffusion

What is diffusion? Ex. Glucose is more highly concentrated in

the blood than it is in the body cells, therefore, glucose diffuses from the blood into the body cells.

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Veins

Like those of the arteries they have three layers, with muscle in the middle layer

The walls of veins are generally much thinner than those of arteries Many veins are located near skeletal muscles, the

contraction of the muscles helps push the blood along Larger veins in your body have valves that prevent

blood from flowing backward Breathing movements which exert a squeezing

pressure against veins in the chest, also force blood toward the heart

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Blood Pressure

Blood pressure is caused by the force with which the ventricles contact

As blood moves away from the heart, blood pressure decreases

The farther away from the ventricle the blood moves the lower its force

Blood flowing near the heart arteries exerts the highest pressure

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Measuring blood pressure

Blood pressure can be measured with a sphygmomanometer

Blood pressure is expressed in millimeters of mercury

First number is a measure of the blood pressure while the heart’s ventricles contract and pump blood into the arteries

Second number measure the blood pressure while the ventricles relax

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1. What does the cardiovascular system consist of?

Heart Blood vessels Blood

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2. What materials does the cardiovascular system deliver throughout the body?

Oxygen Glucose

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3. How does the cardiovascular system get rid of carbon dioxide

Carbon dioxide is passed from cells into the blood and then carried to the lungs where it is exhaled

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4. What are the four chambers of the heart?

Right atrium Left atrium Left ventricle Right ventricle

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5. Which chambers contain oxygen rich blood?

The left atrium and left ventricle

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6. What are the two loops of blood flow?

heart to the lungs and back to the heart Heart to the body and back to the heart

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7. When blood is pumped to the body cells is it oxygen rich?

Yes, it has just come from the lungs where it released carbon dioxide and picked up oxygen

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8. What color is oxygen poor blood?

Dark red

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9. What are you feeling when you take a pulse?

A spurt of blood pushing the artery walls and making them expand

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10. Why are capillary walls so thin?

Materials must be able to pass easily between them and body cells

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11. What happens to the force of blood as it moves away from the heart?

It decreases

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12. Where does blood returning from the body enter the heart?

Right atrium