Blood Vessels & Tissue Formation

Question 1

Arteries Structure and Function:

Answer 1

1. Thick smooth muscle tissue.Can contract and control to maintain pressure.
2. Thick elastic tissue.Can stretch as ventricles contract and recoil as ventricles relax, to maintain high pressure
3. Thick wall. Withstands high pressure / prevents bursting.
4. Smooth / folded endothelium
   Reduces friction / can stretch
5. Narrow lumen.Increases / maintains high pressure

Question 2

Arterioles Structure and Function:

Answer 2

1. Direct blood to different capillaries / tissues.
   2.Thicker smooth muscle layer than arteries. Contracts narrows lumen (vasoconstriction) reduces blood flow to capillaries. Relaxes widens lumen (vasodilation) increases blood flow to capillaries
2. Thinner elastic layer pressure surges are lower (as further from heart / ventricles)

Question 3

Structure of Capillaries and Function:

Answer 3

1. Function is to allow efficient exchange of substances between blood and tissue fluid.
2. Wall is a thin (one cell) layer of endothelial cells Reduces diffusion distance
3. Capillary bed - large network of branched capillaries Increases surface area for diffusion.
4. Small diameter / narrow lumen Reduces blood flow rate so more time for diffusion.
5. Pores in walls between cells Allow larger substances through

Question 4

Explain how the structure of veins relates to their function:

Answer 4

1. Function – carry blood back to heart at lower pressure.
2. Wider lumen than arteries → less resistance to blood flow
3. Very little elastic and muscle tissue blood pressure lower
4. Valves prevent backflow of blood

Question 5

Explain the formation of tissue fluid:

Answer 5

At the arteriole end of capillaries:
1. Higher blood / hydrostatic pressure inside capillaries (due to
contraction of ventricles) than tissue fluid (so net outward force)
2. Forcing water (and dissolved substances) out of capillaries
3. Large plasma proteins remain in capillary

Question 6

Explain the return of tissue fluid to the circulatory system
At the venule end of capillaries:

Answer 6

1. Hydrostatic pressure reduces as fluid leaves capillary (also due to friction)
2. (Due to water loss) an increasing concentration of plasma proteins lowers water potential in capillary below that of tissue fluid
3. Water enters capillaries from tissue fluid by osmosis down a water potential gradient
4. Excess water taken up by lymph capillaries and returned to circulatory system through veins

Question 7

Suggest and explain causes of excess tissue fluid accumulation
● Low concentration

Answer 7

1. Low concentration of protein in blood plasma
2. Water potential in capillary not as low water potential gradient is reduced
3. So more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis
4. Lymph system may not be able to drain excess fast enough

Question 8

Suggest and explain causes of excess tissue fluid accumulation
high blood pressure

Answer 8

1. High blood pressure (eg. caused by high salt concentration) → high hydrostatic pressure
2. Increases outward pressure from arteriole end AND reduces inward pressure at venule end
3. So more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis
4. Lymph system may not be able to drain excess fast enough

Question 9

What is a risk factor? Give examples for cardiovascular disease

Answer 9

1.An aspect of a person’s lifestyle or substances in a person’s body / environment
2. That have been shown to be linked to an increased rate of disease
3. Examples - age, diet high in salt or saturated fat, smoking, lack of exercise, genes