Circulatory System Outline
Parts of the System
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heart, blood, blood vessels
Types of blood vessels
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artery, vein, capillary
Function of the heart
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valve
To act like a pump to circulate blood throughout the body
Why?
o To deliver materials to all the cells of the body and to pick up waste that needs to be removed
Function and Structure of Blood Vessels
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Arteries
o Function: To transport blood with oxygen (oxygenated) away from the heart to the body. They
usually transport blood with oxygen (oxygenated) away from the heart towards the body.
(exception: the artery that takes blood from the heart to the lungs with little/no oxygen)
o Structure: large blood vessel; thick, elastic walls, expand and contract to withstand blood pressure
from the heart
Veins
o Function: To transport (return) blood to the heart from the body. They usually transport blood
without oxygen (unoxygenated) towards the heart from the body. (exception: the vein that takes
blood from the lungs to the heart with oxygen)
o Structure: thinner walls than arteries; need body muscles to contract veins and move blood back
towards the heart; valves help move the blood in the correct direction
Capillaries
o Function: To exchange materials with the cells of the body (oxygen, nutrients, water, waste
products)
o Structure: tinniest of blood vessels; walls are only 1-cell thick; connect arteries to veins
o How do materials get exchanged?
 Animal cells have a semi-permeable cell membrane that contain pores (tiny holes) that act
like doors to allow materials to enter and exit. The capillary walls are made of cells. So, the
cells of the capillary walls allow materials to pass through them and into the body’s cells and
vice versa.
Blood Flow in the Human Body & Heart
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Think of it as two loops!
One loop contains O2, and one does not
General Blood Flow is: Heart (R)
Lungs
Heart (L)
Body
Repeat
Blood without oxygen enters the right side of the heart and gets sent to the lungs to pick up O2 and drop off
CO2. Blood with oxygen enters the left side of the heart and gets sent out of the heart to the body to drop off
oxygen, it also picks up and/or drops off other materials along the way (ex. nutrients/water from the
intestines, waste from body cells/organs, etc.)
Additional Facts
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Human body contains ~5.5 liters
Aorta is the largest artery
Red blood cells carry oxygen
White blood cells fight infection
Blood is mostly water
Materials the blood transports are carried in the liquid part of blood (except for oxygen)
Images of the above information:
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Blood flow through the heart
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Oxygen and Carbon Dioxide exchange in the lung