Arteries, veins & capillaries

Question 1

Arteries, veins & capillaries

Answer 1

1. lining made of single, thin layer of cells called endothelium
2. very smooth to reduce friction

Question 2

Arteries

Answer 2

1. blood leaves heart at high pressure (120mmHg)
2. strong walls to withstand pressure
3. achieved by thickness and composition of wall
4. tunica media = thickest part
5. lumen relatively small to maintain high pressure

Question 3

Artery wall

Answer 3

1. contains collagen, a fibrous protein, giving strength and allows to withstand high pressure
2. elastic tissue allows to stretch & recoil when heart pumps (felt as pulse)
3. recoil maintains high pressure whilst heart relaxes
4. contains smooth muscle that can contract and constrict artery
5. folded endothelium that can unfold when artery stretches

Question 4

Capillaries

Answer 4

1. very thin walls allow exchange of materials between blood & cells via diffusion
2. walls: single layer of flattened endothelial cells -> reduces diffusion distance
3. very narrow lumen -> same diameter as RBC so they are squeezed which helps give up their oxygen

Question 5

Veins

Answer 5

1. returns blood to heart at pressure (5mmHg)
2. no need to have thick walls due to low pressure
3. walls have thin layers of collagen, smooth muscle & elastic tissue -> don’t need to stretch & recoil
4. relatively large lumen eases blood flow
5. overcomes low pressure through valves and muscles next to veins that contract

Question 6

Arterioles

Answer 6

1. links arteries to capillaries
2. more smooth muscle
3. less elastin and collagen than arteries

Question 7

Venules

Answer 7

1. collect blood from capillaries bed and lead into veins
2. wall consists of thin layers of smooth muscle
3. and elastic tissue outside endothelium
4. thing outer layer of collagen