VESSELS + TISSUE FLUID FORMATION Flashcards
Describe two precautions for a student to take when clearing away a dissection (2 marks):
- Disinfect all surfaces and wear gloves
- Wash sharp instruments by holding their handle
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
What factor limits the minimum internal diameter of the lumen of a capillary?
Width of blood cell
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
What is teh pathway which a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs?
- renal vein
- vena cava to right atrium
- right ventricle to pulmonary artery
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
How does the elastic tissue in the wall of an artery help to even out blood pressure?
Stretches as a result of high pressure/ surge of blood and then recoils
Explain the link between the maximum value of the arterial pressure and the events of the cardiac cycle:
Corresponds to ventricles contracting
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
Explain how tissue fluid is formed and how it may be returned to the circulatory system (6 marks):
- Hydrostatic pressure of blood high at arterial end
- Fluid/ water/ soluble molecules pass out
- Proteins/ large molecules remain
- Lowers water potential- becomes more negative
- Water moves back into venous end of the capillary via osmosis/ diffusion
- Lymph system collects any excess tissue fluid which returns to blood
What causes decrease of pressure along the capillary?
Loss of fluid/ volume
Some diets may result in a low concentration of protein in food plasma. This causes the accumulation of tissue fluid. Explain the link between a low concentration of protein in fluid F and the accumulation of tissue fluid. (3 marks)
- water potential in capillary is not as low
- more tissue fluid formed at arteriole end
- less/ no water absorbed into blood capillary by osmosis
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
The water potential of the blood plasma is more negative at the venue end of the capillary than at the arteriole end of the capillary. Explain why. (3 marks)
- Water has left capillary
- Proteins in blood too large to leave capillary
- Giving a higher concentration of blood protein and thus Water potential
Explain why a lack of protein causes a build up of tissue fluid (3 marks):
- WP in capillary is not as low
- Less water removed
- By osmosis
How could high sodium concentrations in medicines affect blood volume? (3 marks)
- Sodium ions lower the WP of the blood
- Water would move into the blood via osmosis
- Increases the blood volume
