structure of blood vessels

Question 1

what is the role of arteries?

Answer 1

they carry blood away from the heart and into arterioles (under high pressure)

Question 2

what is the role of arterioles?

Answer 2

smaller arteries that control blood flow from arteries to capillaries

Question 3

what is the role of capillaries?

Answer 3

tiny vessels that link arterioles to veins

Question 4

what is the role of veins?

Answer 4

carry blood from capillaries back to the heart

Question 5

what do arteries, arterioles and veins all have in common?

Answer 5

the same basic layered structure

Question 6

what is this structure (from the outside inwards)?

Answer 6

tough fibrous outer layer - that resists pressure changes from both within and outside

muscle layer - that can contract and so control the flow of blood

elastic layer - that helps to maintain blood pressure by stretching and springing back (recoiling)

thin inner lining (endothelium) - that is smooth to reduce friction and thin to allow diffusion.

lumen - central cavity of the blood vessel through which the blood flows.

Question 7

what is different about each type of blood vessel?

Answer 7

the relative proportions of each layer - differences in structure are related to differences in the function of the vessel

Question 8

how are the structure of arteries related to their function?

Answer 8

thicker muscle layer compared to veins - smaller arteries can be constricted and dilated in order to control the volume of blood passing through them

thicker elastic layer compared to veins - keeps blood pressure in arteries high for blood to reach the extremities of the body.

overall very thick wall - resists the wall bursting under pressure.

there are no valves (except in arteries leaving the heart) - blood is under constant high pressure, so it tends not to flow backwards.

Question 9

how are the structure of arterioles related to their function?

Answer 9

thicker muscle layer compared to arteries - contraction of muscle layer constricts lumen, restricting flow of blood.

thinner elastic layer compared to arteries - blood pressure is lower.

Question 10

how are the structure of veins related to their functions?

Answer 10

thinner muscle layer compared to arteries - carry blood away from tissues