The circulatory systemChapter 23

• Internal transport• Compare the mammalian system to that of a

fish.• Function and location of organs.• Trace blood flow through the body.• Study the heart beat and cardiac cycle.• Diseases.

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selection• Next weeks lab is on Circulation

The Circulatory System

Overview• The circulatory system transports gases, nutrients,

and wastes• Different body designs demand a heart for

pumping blood to the tissues because gravity opposes blood circulation

• Muscles contract around the blood vessels and work together with valves to pump blood to the heart

• Skin and connective tissue keep blood vessels from enlarging

Capillaries and diffusionFig 23.5

Capillaries and diffusionFig 23.1B

The circulation reaches all cells• Diffusion is insufficient for moving

substances over large distances• Capillaries are the smallest vessels, and

reach all cells• RBC’s exchange materials with the

interstitial fluid.• O2 and nutrients diffuse to the tissues and

wastes and CO2 diffuse to the blood• Homeostasis is maintained in the blood by

the liver and kidney

Types of internal transport Fig 23.2

Types of Internal transport

• Gastrovascular cavity– Digestion and respiration occur in the same

cavity– Intricately branched system that allows water to

bathe the entire system, fluid moved by flagella– Not good in animals with thick multiple layers

of cells

Types of internal transport Fig 23.2

What other system is here but not shown?

Types of Internal transport

• Open circulatory system– Found in Arthropoda and Mollusca– Blood pumped by hearts through open ended

vessels - no interstitial fluid– Fluid is called hemolymph– Contracts -heart pumps blood out of the sinuses– Relaxes - heart draws hemolymph into the

circulatory system

Closed Circulatory System

Fig 23.2

Types of Internal transport

• Closed circulatory system– Blood is confined to vessels, keeping it separate

from the interstitial fluid– Arteries carry blood away from the heart, veins

carry blood to the heart– Fish Gills- gill capillaries- two chambered

heart- atrium - ventricle

Evolution of cardiovascular systems

Fish vs mammal• Fish have a single circuit of blood flow,

with the heart receiving and pumping oxygen poor blood flow

• Mammals have two circuits, a four chambered heart, two atria and two ventricles– Pulmonary right side - blood to lungs– Systemic - left side to the body

• Double system - rapid delivery of oxygen to support high activity

A trip through the cardiovascular system

A trip through the cardiovascular system

• Heart is size of fist- composed of cardiac muscle -cells are electrically connected by intercalated disks

• Atria are thin walled and receive blood, ventricles are thick walled and pump blood.

• AV valves separate the atria and ventricles, Semilunar valves separate the heart and the circulation (pulmonary and systemic)

• Valves maintain flow in one direction• Learn the flow!

Structure and function of blood vessels

Structure and function of blood vessels• Capillaries - supply cells, thin walled, single layer

of epithelial cells and a basement membrane. Promotes diffusion of material to and from the interstitial fluid.

• Arteries - pressure vessels that are thick walled, contain smooth muscle and connective tissue

• Arteioles- small vessels that control flow by changing diameter

• Veins -capacitance vessels- hold much blood -more elastic than arteries, contain valves to prevent backflow of blood

Cardiac cycle

Cardiac Cycle• The heart passively fills with blood, then actively

contracts pumping out blood• Diastole- blood fills the heart while it is relaxed,

all the valves are open• Systole- atria contact and force blood to ventricles,

ventricles contract next forcing the AV valves closed and semilunar valves open - blood is pumped to the body

• Lubb = closing of AV valve, Dubb=closing of semilunar valve

• Cardiac output - amount of blood leaving heart each beat, 75 ml per beat

Pacemaker

Pacemaker and heartbeat

• SA node or pacemaker maintains the heartrate in the wall of the right atrium

• Generates electrical signals that travel to the atria, then to the ventricles

• The AV node delays the signal allowing the ventricles to fill before they contract

• The heart is regulated autonomically just like the lungs

• A slight decrease in blood pH increased heartrate

Heart Attack

Heart Attack•Death of cardiac cells resulting from lack of blood delivered to the heart•Coronary artery blockage

•Dietary influences narrow arteries, blood clots block the arteries

•Angina•Corrective surgery

•Coronary bypass•Balloon angioplasty

Blood pressure and flow in arteries

Pressure declinesVelocity declinesFlow reduced from Frictionarea increasedGarden hose analogy

Blood pressure and flow in arteries• Blood pressure - force that blood exerts against

the walls of blood vessels • Pulse - stretching of arteries causes by pressure of

blood from the heart during systole• Caused by pumping of heart against the resistance

of the smaller blood vessels, greatest in aorta then decreases with distance form the heart

• Blood flow (velocity) decreases with distance from the heart lowest in the capillaries. This allows for maximum diffusion

Blood flow in veins

Blood flow in veins

• Pressure in the veins is near zero• How does it return to the heart?

– Skeletal muscle pumps the veins– Valves allow the blood to flow only to the heart– Breathing also helps by enlarging the veins

around the heart

Measuring blood pressure

Measuring blood pressure• Blood pressure varies throughout the body• 120/70 - 120 @ systole and 70 during diastole• Sphygomomanometer

– Cuff cuts off pressure, systole pushes blood through when the pressure is reduced

– Diastole - when turbulent sounds are no longer heard

• Hypertension - a consistent BP of 140/90 or higher– Pumping against greater resistance wears out the heart– athlerosclerosis

Figure 23.12 Atherosclerosis: normal artery and artery with plaque

Smooth muscle controls the distribution of blood

Smooth muscle controls the distribution of blood

Smooth muscle controls the distribution of blood

• Blood flow is constant to the heart and brain, but varies in other tissues

• Constriction of the arterioles reduces flow to the capillaries, it is controlled by nerves and hormones

• Precapillary sphincters control blood flow into capillary beds

• Meals- capillary beds in the digestive tract receive more blood after eating

Capillary transfer of substances

Capillary transfer of substances

Transfer of substances• Movement across the membrane occurs by

diffusion, endocytosis, osmosis• Capillaries are the only vessels small

enough• Water, sugar, salt,and O2, leak through

small cracks between epithelial cells• Blood pressure tends to actively force fluid

out of capillaries• Osmosis tends to cause fluids to move in• Arteries = hi pressure, veins = low pressure

Structure and function of blood

• Blood consists of cells suspended in plasma• Avg blood volume = 4-6 liters• 45% cells, 55% plasma• Ions/salts maintain osmotic balance and pH• Proteins help in blood clotting and

immunity

Figure 23.14-23.15 Blood smear

Red and white blood cells

• RBC’s -erythrocytes, formed in bone marrow

• Biconcave disk to increases surface area• 250 million molecules of hemoglobin each• RBC’s carry gases• Production of RBC’s controlled by O2

levels and erythropoetin and neg. feedback• Anemia, low iron

Red and white blood cells• WBC’s help defend the body• Leukocytes, help defend the body• Basophils- fight infection by releasing chemicals• Phagocytes- move into body tissue and eat

bacteria and foreign proteins (neutrophils and monocytes)

• Eosinophil -phagocytic and eat protozoans• Lymphocytes -specific defense

Blood clotting

Figure 23.16 Blood clot

Blood clotting

• Blood contains self sealing material, activated after injury

• Involves platelets, fibrinogin, and clotting factors• Tissue damage exposes connective tissue to blood• Pin pricks - platelets adhere and attract other

platelets• Serious cuts - fibrin clot forms, thrombrin,

fibrinogin form fibrin which traps white blood cells

• Hemophilia/ Thrombus

Stem cells

Stem Cells

• RBC’s, WBC’s and platelets all arise from stem cells in the bone marrow

• Leukemia– Overproduction of WBC’s (cancer)– Interferes with gas exchange and clotting