mass transport exam q's

• 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

  -