3.3.4.1 Mass Transportin Animals - Circulation

Question 1

Circulation - pulmonary circulation

Answer 1

• deoxygenated blood is pumped from the right ventricle of heart to the lungs, where it is oxygenated - returns to the left atrium - the pulmonary circulation

Question 2

Systemic circulation

Answer 2

• oxygenated blood is pumped from the left ventricle to the body, where it unloads o2 - then returns to the right atrium

Question 3

Coronary, pulmonary, renal arteries role

Answer 3

Coronary A = supply the cardiac muscle with oxygenated blood

Pulmonary A = veins transport blood to and from the lungs

Renal A and veins = transport blood to and from the kidneys.

Question 4

Aorta and vena cava role

Answer 4

Aorta = transports blood from the heart to the body

Vena cava = retunes blood from the body to the heart

Question 5

Atrial systole (contraction)

Answer 5

• higher pressure in atria than ventricles
• blood moves into the ventricles
• increase ventricular volume, decrease atrial vol
• artrioventricular valves open, semi-lunar valves closed

Question 6

Ventricular systole (contraction)

Answer 6

• higher pressure in ventricles than atria so AV valves shut prevent backflow of blood
• pressure in ventricles higher then the aorta and pulmonary artery - forces Semilunar valves to open
• blood moves into the arteries
• increase arterial volume, decrease ventricular vol.

Question 7

Ventricular & atrial diastole (relaxation)

Answer 7

• ventricles and atria both relax
• higher pressure in the pulmonary artery & aorta - closes the SL valve, prevent back flow blood into the ventricles
• blood returns to the heart and atria fill again
• pressure in atria increases
• ventricles continue to relax, pressure falls bellow pressure of the atria - so AV valves open
• blood flows passively into the ventricles.

Question 8

Arteries - function

Answer 8

• Transport blood under highest pressures, from heart to organs
• Accommodate variations in pressure
• Prevent pressure from falling too quickly

Question 9

How to arteries achieve their function

Answer 9

• thick and muscular walls and elastic tissue: stretch and recoil as the heart beats - helps maintain high pressure
• inner lining (endothelium) is folded: allows arteries to stretch - helps maintain high pressure
• narrow lumen to resist flow & maintain pressure + control flow of blood

Question 10

Arterioles - function

Answer 10

• transport blood under high pressures, from arteries to capillaries
• branch off arteries
• change diameter to control pressure changes & flow of blood to different tissues

Question 11

How do arterioles achieve their function

Answer 11

• thick muscle tissue layer: contract and relax to control changes in rate of flow
• narrow lumen to maintain pressure
• elastic tissue layer: can stretch & recoil to maintain + accommodate pressure pressure

Question 12

Veins - function

Answer 12

• transport blood under lowest pressures, from organs to heart
• maintain pressure so that blood is retuned to the heart

Question 13

How do veins achieve their function

Answer 13

• thin elastic and muscle tissue layer: some ability to contract to maintain pressure
• wide lumen to reduce resistance to flow
• pocket valves: close to prevent the backwards flow of blood

Question 14

Capillaries - structure relates to function

Answer 14

• permeable capillary wall
• single cell thick - reduces diffusion distance
• flattered endothelial cells - reduces diffusion distance
• fenestrations - allows larger molecules through
• narrow diameter - large surface area to vol ratio
• narrow lumen - reduces flow rate giving more time for diffusion

Question 15

Formation of tissue fluid

Answer 15

• in capillaries the hydrostatic pressure is higher at the arterial end
• this pushes fluid out of the capillary
• it is opposed by the water potential of the blood, which is lower than that of the tissue fluid & the hydrostatic pressure of the tissue fluid.
• overall fluid is forced OUT from the capillary by ultrafiltration

Question 16

Return of tissue fluid

Answer 16

• further along the capillary, at the venous end, the hydrostatic pressure falls
• formation of the tissue fluid reduces the water potential of the blood slightly, because the plasma proteins cannot cross the basement membrane, but the vol of water has decreased.
• so fluid moves INTO the capillary, but some tissue fluid drains into the lymphatic system