the circulatory system questions Flashcards
(7 cards)
Why does blood not accumulate in the arterioles, even though the speed of blood flow is greater in the arterioles than the capillaries? (2 marks)
many more capillaries than arterioles
cross sectional area of capillaries is much greater than arterioles
The rise and fall of blood pressure in the aorta is greater than in the small arteries. Suggest why. (3 marks)
Aorta is close to the heart
Aorta has elastic tissue
Aorta has stretch/ recoil
Explain how water from tissue fluid is returned to the circulatory system (4 marks):
Plasma proteins remain
Creates a water potential gradient
Water moves to blood via osmosis
Returns to blood by lymphatic system
Describe two ways in which you would expect blood pressure in a vein to differ from that in an artery (2 marks):
less difference between maximum + minimum in a vein
pressure in vein is lower
Describe and explain four ways in which the structure of a capillary adapts from the exchange of substances between blood and the surrounding tissue (4 marks):
Permeable capillary wall
Single cell thick- reduces diffusion distance
Flattened endothelia cells- reduces diffusion distance
Fenestrations- allows large molecules through
Small diameter gives a large SA:V ratio
How does high blood pressure lead to an accumulation of tissue fluid?
High blood pressure= high hydrostatic pressure
Increases outward pressure from arteriole end of capillary
So more tissue fluid formed
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the right aorta (5 marks)
Atrium has a higher pressure than the ventricles- causing AV valves to open
Ventricle has higher pressure than atrium, causing AV valves to close
Ventricle has higher pressure than aorta, causing SL valves to open
higher pressure in aorta than ventricle causing SL valves to close
Muscle contraction causes increase in pressure
