the heart and the cardiovascular system

7/31/2019 The Heart and the Cardiovascular System

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The heart is composed of two independentpumping systems, one on the right side, andthe other on the left. Each has two chambers,an atrium and a ventricle. The ventricles arethe major pumps in the heart.


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The external structures of the heart includethe ventricles, atria, arteries, and veins.Arteries carry blood away from the heartwhile veins carry blood into the heart. The

vessels colored blue indicate the transport ofblood with relatively low content of oxygenand high content of carbon dioxide. Thevessels colored red indicate the transport ofblood with relatively high content of oxygenand low content of carbon dioxide.


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The right system receives blood from theveins of the whole body. This is "used" blood,which is poor in oxygen and rich in carbondioxide.

The right atrium is the first chamber thatreceives blood.

The chamber expands as its muscles relax

to fill with blood that has returned fromthe body.


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The blood enters a second muscular chambercalled the right ventricle.

The right ventricle is one of the heart's twomajor pumps. Its function is to pump theblood into the lungs.

The lungs restore oxygen to the blood andexchange it with carbon dioxide, which is

exhaled


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The left system receives blood from thelungs. This blood is now oxygen rich.

The oxygen-rich blood returnsthrough veins coming from the lungs

(pulmonary veins) to the heart. It is received from the lungs in the leftatrium, the first chamber on the leftside.

Here, it moves to the left ventricle, apowerful muscular chamber thatpumps the blood back out to thebody.


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The left ventricle is the strongest of theheart's pumps. Its thicker muscles need toperform contractions powerful enough toforce the blood to all parts of the body.

This strong contraction produces systolicblood pressure (the first and higher numberin blood pressure measurement). The lowernumber (diastolic blood pressure) ismeasured when the left ventricle relaxes torefill with blood between beats.


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Blood leaves the heart through the ascendingaorta, the major artery that feeds blood to theentire body.


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Valves are muscular flaps that open and close soblood will flow in the right direction. There arefour valves in the heart:

The tricuspid regulates blood flow between

the right atrium and the right ventricle. The pulmonary valve opens to allow blood to

flow from the right ventricle to the lungs.

The mitral valve regulates blood flow

between the left atrium and the left ventricle. The aortic valve allows blood to flow from

the left ventricle to the ascending aorta.


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The circulatory system (or cardiovascular system)is an organ system that moves nutrients, gases,and wastes to and from cells, helps fight diseasesand helps stabilize body temperature and pH to

maintain homeostasis. While humans, as well asother vertebrates, have a closed circulatorysystem (meaning that the blood never leaves thenetwork of arteries, veins and capillaries), some

invertebrate groups have open circulatorysystem. The most primitive animal phyla lackcirculatory systems.
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Pumps: Circulatory pumps (hearts) are vessels filled

with the circulatory fluid or blood

When muscles around the containercontract they exert pressure on the blood,causing it to flow

Heart type: pump produces a high pressure

which causes blood to flow out througharteries

Muscle pump: muscle contraction squeezesveins, causing blood to flow toward heart


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Tubing or pipes = arteries, capillaries, veins Carry blood toward delivery site

Sometimes deliver within a few microns ofsite (capillaries in tissue)

Blood vessels may be elastic (which helpskeep the pressure high between heartbeats)

Vessels may constrict and dilate (which gives

control over the flow)


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Valves give direction to the flow Blood vessels (including hearts &veins) have flap valves that open in

only one direction Example: when pressure increases inveins this opens valves toward theheart and closes those in the other

direction -> blood flows towardheart


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The purposes of circulation: To deliver food materials and oxygento the tissues

To remove waste products and heat These things can be done by diffusionin a small animal, but in a large animal

a circulation is necessary.


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Right heart:

Pumps to lungs: nearly 100%

of the flow goes through thelungs

Low pressure side: 25 mm Hgsystolic pressure in humans

Right ventricle has thin walls


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Left heart:Pumps to rest of body

High pressure side: 120mm Hg systolic pressure inhumans

Left ventricle has thickwalls


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Right & and left atria:Help fill the ventricles

Very low pressureThin walls


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Pumping of the right & liftsides occurs together

Must be accurately balanced,otherwise fluid mayaccumulate in the lungs

(pulmonary edema)


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The muscle pump helps returnblood to the heart When muscles contract the veins

passing through them are squeezed

This causes blood to flow towardthe heart

Valves prevent flow away from theheart


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Your body has approximately 5

liters of blood (large people have alittle more, small people a little less)

The heart's pumping rate is called

the cardiac output: at rest its valueis about 5 liters/min


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Comparing the volume with thecardiac output you can see that theentire blood volume passes through

the heart on the average once everyminute All of the output from the right heartgoes through the lungs (5 liters/min)

The output from the left heart splitsand goes through different organs


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the heart and the cardiovascular system

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