blood vessels Flashcards
(27 cards)
what does the aorta do?
transports blood away from the left ventricle under very high pressure, smooths out surges in blood pressure
what do arteries do?
carry blood away from the heart under high pressure
what do arterioles do?
transport blood away from the heart, connect to capillaries and control blood flow into these capillaries
what do capillaries do?
exchange materials between the blood and cells of the body
what do venules do?
transports blood away from capillaries
what do veins do?
transports blood back to the heart and acts as a blood reservoir
what does the vena cava do?
returns blood back to right atrium
arteries, arterioles and veins all have the same basic layered structure, what is this?
-tough fibrous outer layer
- (smooth) muscle layer
-elastic layer
-endothelium
-lumen (not actually a layer but central cavity of vessel that allows blood to flow)
describe the structure of arteries related to their function?
thick muscle wall to withstand the high pressure of the vessel
thick elastic wall;
-when ventricles contract and blood flows into arteries, the pressure is higher and elastic tissue in the wall stretches to smooth out surges in blood pressure
-when ventricles relax the elastic tissue recoils and this maintains the pressure
lumen small diameter and lined with endothelial tissue that is smooth and reduces resistance to flow
aorta/pulmonary artery have a semi-lunar valve to prevent backflow of blood into ventricles
arteries generally have no valves (except semi-lunar in aorta and pulmonary artery) why is this?
high pressure blood tends not to flow backwards
how do arterioles control blood flow into capillaries?
by contracting or relaxing the smooth muscle in their walls by vasoconstriction and vasodilation
how does vasoconstriction occur and what is the benefit of it?
occurs by smooth muscle in walls of arterioles contracting to decrease diameter of lumen
reduces blood flow to skin capillaries and diverts blood supply to muscles
when might vasoconstriction be required?
when you’re cold because it can reduce blood flow to skin and so reduce heat loss
to decrease blood flow to other organs e.g. in digestive system and divert blood to muscles during exercise
how does vasodilation occur and what is the benefit of it?
smooth muscle in arteriole wall relaxes and lumen diameter increases which increases blood flow to capillaries
increases blood flow to skin capillaries and increases blood supply to muscles
when might vasodilation be required?
increase blood flow to muscles during exercise
to cool down by increasing blood flow to skin capillaries
how do the walls of arterioles compare to arteries?
muscle layer relatively thicker than in arteries to allow for vasoconstriction and vasodilation to control blood flow into capillaries
elastic layer is relatively thinner because blood pressure is lower
describe the structure of veins which is linked to their function?
- smooth muscle layer is relatively thin because they carry blood to the heart, so don’t need to control blood flow
-elastic layer relatively thin because of lower pressure
-valves at intervals throughout to ensure blood won’t flow backwards, which it might otherwise due to gravity and low pressure
-lumen is large so there is less resistance to blood flow
-veins have a lower total cross-sectional area and this area decreases as the smaller veins join into bigger ones- gives an increased velocity of blood flow return to heart
what happens to veins when body muscles contract?
veins are compressed which increases the pressure of the blood within them
valve opens to ensure blood is pushed towards the heart
valves close to prevent backflow of blood when the muscles relax
what is the one tissue capillary walls are made from?
endothelial
what can be said about the cells in the tissue of capillary walls, how does this relate to its function?
flatted cells provide a short diffusion pathway for a faster rate of diffusion across capillary wall
walls one cell thick
how much blood can pass through a capillary at one time and what is the advantage of this?
only one red blood cell can pass through at any time so slows down blood flow to allow more time for diffusion- there is greater resistance to flow since they’re so narrow
what feature gives capillaries a large total cross sectional area? what is the benefit of this?
highly branched- this gives a lower velocity of blood and more time for exchange to occur
what do spaces between the endothelial cells in capillary walls allow for?
fenestrations allow fluid to move out of capillaries with less resistance to flow
what is the pre-fix for blood vessels carrying blood to/away from the liver?
hepatic
