Blood vessles

Question 1

Names are require only of the coronary arteries, blood vessels entering an leaving the heart, liver and kidneys

Answer 1

Question 2

Artery

Answer 2

away from heart

thickest wall enabling it carry blood at high pressures

elastic tissue smoothes out flow

muscle in wall controls flow

endotheium reduces friction

Question 3

Vein

Answer 3

to the heart

thin wall

less elastic tissue

less muscle

larger lumen

valves

muscle contraction

endothelium reduces friction

Question 4

Capillary

Answer 4

thin wall so short diffusion pathway

fenestrations to allow minerals to be exchanged

narrow lumen

Question 5

Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their

functions.

Answer 5

Elastic tissue

1 Elastic tissue stretches under pressure/when heart beats;

2 Recoils/springs back;

3 Evens out pressure/flow;

Muscle

4 Muscle contracts;

5 Reduces diameter of lumen/vasoconstriction/constricts vessel;

6 Changes flow/pressure;

Epithelium

7 Epithelium smooth;

8 Reduces friction/blood clots/less resistance;

Question 6

The thickness of the aorta wall changes all the time during each cardiac cycle. Explain why.

Answer 6

1. (Aorta wall) stretches;
2. Because ventricle/heart contracts / systole / pressure increases;
3. (Aorta wall) recoils;
4. Because ventricle relaxes / heart relaxes /diastole / pressure falls;
5. Maintain smooth flow / pressure

Question 7

Explain the difference in thickness between the pulmonary artery (thicker) and the pulmonary vein (thinner).

Answer 7

High pressure / smooth out blood flow / artery wall contains more collagen / muscle / elastic (fibres) / connective tissue;

Question 8

Describe two ways by which blood flow in the veins is maintained.

Answer 8

Valves prevent backflow;
effect of (skeletal) muscle contraction

Residual blood pressure from heart;
negative pressure from thorax;
‘suction effect’ from heart;

Question 9

Describe and explain ways in which a capillary adapts for exchange

Answer 9

1. Permeable capillary wall/membrane;
2. Single cell thick/thin walls, reduces diffusion distance;
3. Flattened (endothelial) cells, reduces diffusion distance;
4. Fenestrations, allows large molecules through;
5. Small diameter/ narrow, gives a large surface area to volume/ short diffusion distance;
6. Narrow lumen, reduces flow rate giving more time for diffusion;
7. Red blood cells in contact with wall/ pass singly, gives short diffusion distance / more time for diffusion;
   (allow 1 mark for 2 features with no explanation)

Question 10

Explain two ways in which the small diameter of the capillaries results in the efficient transfer of oxygen from the alveoli to the red blood cells.

Answer 10

Red blood cells close to capillary wall/ thin capillary wall;
Short diffusion path/ distance for oxygen to diffuse;
Longer time for diffusion to take place/ diffusion is slow;

Question 11

Explain how tissue fluid is formed and how it may be returned to the circulatory system.

Answer 11

1. (Hydrostatic) pressure of blood high at arterial end;
2. Fluid/water/soluble molecules pass out (reject plasma);
3. Proteins/large molecules remain;
4. This lowers the water potential / water potential becomes more negative;
5. Water moves back into venous end of capillary (reject tissue fluid);
6. By osmosis / diffusion;
7. Lymph system collects any excess tissue fluid;
8. (Lymph) returns to blood / circulatory system / link with vena cava/returns tissue fluid to vein;

Question 12

Describe how tissue fluid is formed and how it is returned to the circulatory system.

Answer 12

Formation

1. High blood / hydrostatic pressure / pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;

Return

4. Lower water potential in capillary / blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph collecting excess fluid returning blood to main circulation

Question 13

Describe the part played by proteins in the plasma in returning tissue fluid to the capillary.

Answer 13

Produces lower water potential;

Water moves into capillary;

By osmosis/diffusion;

Question 14

Describe and explain one way in which the composition of tissue fluid differs from that of plasma.

Answer 14

Contains little/no protein;

Molecules too large (to pass through capillary wall);

Contains less glucose;
some will have entered tissue cells;

Question 15

The tissues of people who are starving often swell because of the accumulation of tissue fluid. Explain what causes this accumulation of tissue fluid.

Answer 15

Starvation linked to low protein content of diet/Low protein concentration
in plasma/blood;
Water potential of blood higher/smaller water potential gradient;
Tissue fluid formed faster than returned/less tissue fluid returned to blood;

Question 16

Histamine

Answer 16

increases the permeability of capillary walls so that large molecules can pass through. Explain how this change in permeability results in swelling round the bite.

Proteins can move into tissue fluid;
Lowers water potential of tissue fluid;
Increases tendency to draw water/fluid out/
Reduces tendency to reabsorb water;

Question 17

Suggest an explanation for the link between high blood pressure and the accumulation of tissue fluid.

Answer 17

High blood pressure increases rate of filtration / forces more fluid out;
Lymph system cannot cope / higher pressure reduces reabsorption