The Circulatory System
Blood doesn’t accumulate in arterioles because capillaries are far more numerous, giving a much greater total cross-sectional area. The aorta shows greater blood pressure fluctuation due to its proximity to the heart and presence of elastic tissue for stretch and recoil. Water from tissue fluid returns to the blood via osmosis, driven by a water potential gradient created by plasma proteins, or via the lymphatic system.
Why does blood not accumulate in the arterioles, even though the speed of blood flow is greater in the arterioles than the capillaries?
many more capillaries than arterioles
cross sectional area of capillaries is much greater than arterioles
Key Terms
Why does blood not accumulate in the arterioles, even though the speed of blood flow is greater in the arterioles than the capillaries?
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.
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
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
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
Permeable capillary wall
Single cell thick- reduces diffusion distance
Flattened endothelia cells- reduces diffusion distance
Fenestration...
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
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| Term | Definition |
|---|---|
Why does blood not accumulate in the arterioles, even though the speed of blood flow is greater in the arterioles than the capillaries? | many more capillaries than arterioles |
The rise and fall of blood pressure in the aorta is greater than in the small arteries. Suggest why. | Aorta is close to the heart |
Explain how water from tissue fluid is returned to the circulatory system | Plasma proteins remain |
Describe two ways in which you would expect blood pressure in a vein to differ from that in an artery | less difference between maximum + minimum in a vein |
Describe and explain four ways in which the structure of a capillary adapts from the exchange of substances between blood and the surrounding tissue | Permeable capillary wall |
How does high blood pressure lead to an accumulation of tissue fluid? | High blood pressure= high hydrostatic pressure |
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the right aorta | Atrium has a higher pressure than the ventricles- causing AV valves to open |