Bio - SECTION 3 - Mass transport - Qs

Describe how the tissue fluid is returned to the circulatory system

- Hydrostatic pressure lower in capillary and higher in tissues

- Water returns

- by osmosis

- water potential lower in capillary

- due to protein

- returns via lymph

Explain how the elastic tissue in the wall helps to even out pressure of blood flowing through artery

- Stretches as a result of high pressure

- Then recoils

Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

- Atrium has higher pressure than ventricle (due to filling / contraction)

- causing atrioventricular valves to open;

- Ventricle has higher pressure than atrium (due to filling / contraction)

- causing atrioventricular valves to close;

- Ventricle has higher pressure than aorta causing semilunar valve to open;

- Higher pressure in aorta than ventricle (as heart relaxes) causing semilunar valve to close;

- (Muscle / atrial / ventricular) contraction causes increase in pressure;

Explain how their cardiac output could stay the same even when their resting heart rate had decreased.

- Cardiac output = stroke volume × heart rate

- Stroke volume increases / increased size or volume of ventricles. / more blood leaves heart in each contraction

- (Cardiac output is the amount of blood pumped by the heart per min )

Explain why a lack of protein in the blood causes a build up of tissue fluid.

- Water potential (in capillary) not as low / is higher / less negative / water potential gradient is reduced;

- Less / no water removed (into capillary);

- By osmosis (into capillary);

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

- (hydrostatic) pressure of blood high at arterial end;

- fluid / water / are forced out

- proteins / large molecules remain in capillary because they're too large;

- this lowers the water potential

- water moves back into venous end of capillary (reject tissue fluid) by osmosis

- lymph system collects any excess tissue fluid which returns to blood / circulatory system / link with vena cava / returns tissue fluid to vein;

Blood leaving the heart through aorta is at a higher pressure than blood leaving through pulmonary artery. Explain what cause this higher pressure.

- Left ventricle

- has a thicker muscle/wall/stronger contraction

Explain why the presence of carbon dioxide leads to the Bohr effect.

- Carbon dioxide reacts with water to form carbonic acid

- lowering the pH of the blood;

- Hb acts as a buffer to maintain the right pH;

- the change in shape of Hb lowers its affinity for oxygen.

The rise and fall in blood pressure in the aorta is greater than in the small arteries. Explain why

- Aorta close / directly linked to the heart / ventricle / pressure is higher / is very high;

- Aorta has elastic tissue;

- Aorta has stretch / recoil.

Explain one advantage of capillaries being

narrow

- Short pathway / short distance between blood and outside of capillary

The volume of blood leaving the capillary network into the veins is less than the volume of blood entering from the arteries. Explain why.

Fluid) in tissue fluid / (fluid) in lymph

High blood pressure leads to an accumulation of tissue fluid. Explain how

- High blood pressure = high hydrostatic pressure;

- Increases outward pressure from (arterial) end of capillary

- (So) more tissue fluid formed / less tissue fluid is reabsorbed.

The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why.

- Water has left the capillary;

- Proteins (in blood) too large to leave capillary;

- Increasing / giving higher concentration of blood proteins

Explain the difference in thickness between pulmonary artery and pulmonary vein

High pressure / smoothes out blood flow / artery

wall contains more collagen / muscle / elastic

(fibres) / connective tissue;

The thickness of the aorta wall changes all the time during the cardiac cycle, explain why

- Aorta wall stretches;

- Because ventricle/heart contracts / systole /

pressure increases;

- Aorta wall recoils;

- Because ventricle relaxes / heart relaxes

/diastole / pressure falls;

- Maintain smooth flow / pressure;

The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift.

- Lower affinity for oxygen = oxygen released quicker / oxygen dissociates / unloads more readily;

- to respiring muscles / tissues / cells

- for high respiration

Explain how the structures of the walls of arteries and arterioles are related to their functions

Elastic tissue:

stretches under pressure/when heart beats;

- Recoils/springs back;

- Evens out pressure/flow;

Muscle:

- Muscle contracts;

- Reduces diameter of lumen

- Changes flow/pressure;

Epithelium:

- Epithelium smooth;

- Reduces friction/blood clots/less resistance;

What is the function of the coronary arteries?

-Carry oxygen

- To heart muscle/tissues

Other than causing slow blood flow, explain one advantage of capillaries being narrow.

- Short pathway / short distance between blood and outside of capillary

- Large surface area (of blood) in contact with walls of capillaries

- Faster osmosis / diffusion

What factor limits the minimum internal diameter of the lumen of a capillary?

- width/diameter of blood cell

The oxygen dissociation curve of the fetus is to the left of that for its mother. Explain the advantage of this for the fetus.

- Higher affinity / loads more oxygen at low / same high partial pressure

- Therefore oxygen moves from mother / to fetus

Blood leaving the kidney eventually returns to the kidney.

Describe the pattern of blood circulation in a mammal that causes blood to return to the

kidney.

1. blood flows from kidney along renal vein to vena cava;

2. along vena cava to right atrium/side of heart;

3. along pulmonary artery to lungs;

4. along capillaries to pulmonary vein;

5. along pulmonary vein to left atrium/side of heart;

6. along aorta to renal artery (to kidney);

7. Blood may pass through several complete circuits before returning to kidney;

Explain the role of the heart in the formation of tissue fluid.

- Contraction of ventricle(s) produces high blood / hydrostatic pressure;

- This forces water and some dissolved substances out of blood capillaries;

Explain the importance of elastic fibres in the wall of the aorta.

- Stretches when ventricle contracts

- Recoils when ventricle relaxes (diastole)

- Smooths blood flow / maintains blood pressure / reduces pressure surges;

Explain the importance of muscle fibres in the wall of an arteriole.

- (Muscle) contracts;

- (Arteriole) constricts / narrows / alters size of lumen / reduces / regulates blood flow

Explain how the structures of the walls of arteries and arterioles are related to their functions.

Elastic tissue

- Elastic tissue stretches under pressure / when heart beats then recoils / springs back;

- Evens out pressure / flow;

Muscle

- Muscle contracts to reduce diameter of lumen / vasoconstriction / constricts vessel;

- Changes flow / pressure;

Epithelium

- Epithelium smooth;

- Reduces friction / blood clots / less resistance;

In humans, substances move out of the capillaries to form tissue fluid. Describe how this tissue fluid is returned to the circulatory system.

- (Hydrostatic) pressure lower in capillary / blood / higher in tissues /tissue fluid;

- Water (returns);

- By osmosis;

- Water potential lower in blood / capillary and higher water potential in tissues

- Due to protein (in blood);

- (Returns) via lymph (system / vessels);

Explain how oxygen is loaded, transported and unloaded in the blood.

- Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;

- Loading / uptake / association in lungs;

- at high pO2

- Unloads / dissociates / releases to respiring cells/ tissues;

- at low p.O2;

- Unloading linked to higher carbon dioxide concentration;

Describe and explain four ways in which the structure of a capillary adapts it for the

exchange of substances between blood and the surrounding tissue.

- narrow lumen, reduces flow rate giving more time for diffusion;

- small diameter = short diffusion distance

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