Blood Vessels

Question 1

arteries

1. what is the function?
2. oxygen and pressure levels?

Answer 1

1. transports blood away from the heart

2. high oxygen and pressure levels (except pulmonary artery)

Question 2

describe and explain how arteries are structurally adapted to their function. (3)

Answer 2

1. thick, muscular walls: withstand high pressure of blood directly received from heart
2. elastic walls (elastic fibre layer in walls):
   - stretch and recoil, push blood in spurts,
   - give rise to pulse,
   - ensures unidirectional blood flow
3. smaller lumen diameter (compared to vein):
   - high B.P maintained
   - ensure blood continuously moves forward over large distances

Question 3

veins

1. function?
2. oxygen and pressure levels?

Answer 3

1. transports blood towards the heart

2. low oxygen and pressure levels (except pulmonary vein)

Question 4

describe and explain how veins are structurally adapted to their function. (3)

Answer 4

1. presence of semi-lunar valves:
   - prevents back flow of blood
   - ensures unidirectional blood flow
2. situated between skeletal muscles
   - low BP not enuf to pump blood back to heart
   - muscle contractions squeezes veins to pump blood back to heart
3. thinner wall and bigger lumen diameter (compared to artery)
   - low Bp so not needed

Question 5

blood capillaries

1. function?
2. pressure and velocity? why?

Answer 5

1. site of exchg of materials betw blood and tisure fluid
2. low and decreasing pressure (subst exiting + branch out into dense network- larger cross sectional area) ,
3. low velocity (more time for exchg)

Question 6

describe and explain how blood capillaries are structurally adapted to their function. (4)

Answer 6

1. 1 cell thick endothelium
   - decreases diffusion dist, faster rate of exchg
2. pores betw endothelial cells
   - regulate entry/exit of small soluble materials (accounts for partial permeability of endothelium)
3. dense network of capillaries
   - transport blood away from exchg surface quickly
   - steep concentration gradient, increase rate of diffusion & exchg of subst
4. narrow lumen size
   - RBCs move in single file, more time for exchg

Question 7

vascular pressure (pressure in vessels):

1. as blood flows from aorta to capillaries to vena cava, pressure decreases. why? (3)
2. pressure in arteries/arterioles/aorta fluctuates. why?

Answer 7

1. • p decreases as dist travelled by blood increases
   • branching of cap, total cross sectional area increase, p decreases, b velocity decreases
   • subst exit at cap, lesser subst in b.c
2. constant contraction and relaxation of aterial walls, b.p increases and decreases repeatedly

Question 8

process of exchg of materials betw blood capillaries and tissue fluid:

describe movement of oxygen, glucose and amino acids GAA (5)

Answer 8

1. at arteral end bp is high as closer to heart
2. at venous end bp is lower
3. creates high hydrostatic pressure in blood cap
4. oxygen, glucose, AA and blood plasma exits blood cap and into tissue fluid
5. respiring cells low concentration of O2+GAA(as constantly used up), diffuse into respiring cells

Question 9

process of exchg of materials betw tissue fluid and respiring cells:

describe movement of carbon dioxide and urea at the blood capillaries (2)

Answer 9

1. respiring cell higher concentration of CO2+urea, diffuse into tissue fluid
2. blood cap low concentration of CO2+urea (constantly transported away), diffuses into blood capillary

Question 10

how is tissue fluid/ interstitial fluid formed? (2)

Answer 10

1. BP at arteral end of capillary is higher than at venous end, creating higher hydrostatic pressure in blood capillary than in interstitial fluid
2. blood plasma forced out of blood cap, forming new interstitial fluid (plasma proteins too big)