Fluids, oedema Flashcards
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 fluid2. Water (returns)3. By osmosis4. Water potential lower/more negative in blood/capillary / higher/less negative water potential in tissues / via water potential gradient5. Due to protein (in blood)6. (Returns) via lymph (system/vessels)
Explain how tissue fluid is formed and how it is returned to the circulation
1) At the start of the capillary bed, nearest the arteries, the pressure inside the cappilaries is greater than the pressure in the tissue fluid. The difference in pressure forced the fluid out of the cappilaries and into the spaces forming tissue fluid (pressure filtration)2) As fluid leaves, the pressure reduced in the capillaries - so the pressure is much lower at the end of the cappilary bed thats nearest to the veins.3) due to fluid loss, the water potential at the end of the cappilaries nearest the veins is lower than the water potential in the tissue fluid - so some water re-enters the cappilaries from the tissue fluid at the vein end by osmosis
Give one way in which plasma is different from tissue fluid
More/larger proteins less urea/carbon dioxide more glucose/amino acids/fatty acids/oxygenhigh( hydrostatic) pressure
The blood pressure is high at the start of the capillary. Explain how the left ventricle causes the blood to be at high pressure.
Contracts
In children, some diets may result in a low concentration of protein in plasma. This can cause the accumulation of tissue fluid. Explain the link between a low concentration of protein in plasmaand the accumulation of tissue fluid.
Water potential (in capillary) not as low/is higher/less negative / water potential gradient is reducedMore tissue fluid formed (at arteriole end)Less/no water absorbed (into blood capillary)by osmosis; (into blood capillary)
