tissue fluid formation Flashcards
what is tissue fluid made from
-substances that leave the blood plasma e.g. o2, nutrients, h20
what does tissue fluid not contain
-red blood cells or big proteins as they’re too large to pass through capillary walls
what is the function of tissue fluid
-cells take in 02 and nutrients from tissue fluid and release metabolic waste into it
-substances move out via pressure filtration
step one of tissue fluid formation
-at the arterial end, the hydrostatic pressure inside capillaries is greater than the hydrostatic pressure in the tissue fluid
-difference in pressure forces fluid out of the capillaries into the spaces around the cells
what happens after step one (step one part two LOL)
-as the fluid leaves, the hydrostatic pressure reduces in the capillaries
-making hydrostatic pressure much lower in the venous end
step two of the tissue fluid formation
-at the venule end of capillary bed the water potential in capillaries is lower than the water potential in the tissue fluid
what is the oncotic pressure generated by in the second step of tissue fluid formation
generated by plasma proteins present in capillaries which lower water potential
why in step two is the water potential in the capillaries lower than the water potential in the tissue fluid
due to the fluid loss from capillaries and high oncotic pressure
step three of the tissue fluid formation
-some water reenters the capillaries from tissue fluid at venule end by osmosis
what is ultrafication and when does it happen
-it is when small molecules such as water, ions or waste products like co2 are filtered out of the blood
-happens at the arterial end when blood pressure (hydrostatic pressure) forces stuff out
why is water drawn back into the capillaries
-the plasma proteins that are too big to diffuse out remain in the capillaries (making a -ve solution inside)pulling in water
where does excess tissue fluid go
-directed into another tubular system called the lymph system/lymphatic system
where does the excess tissue fluid go
-return to blood system via the subclavian vein in the chest
what’s the hydrostatic pressure
-pressure that fluid exerts when pushing against the sides of a vessel or container
what’s the oncotic pressure
-pressure created by the osmotic effect of the solutes
job of hydrostatic pressure
-in the blood, pushes fluid out into tissues
-in the tissue fluid, push fluids back into capillaries
job of oncotic pressure
-of the blood, pulls water back into the blood
-of the tissue fluid, pulls water into the tissue fluid
what remains in the blood in vessels
-all RBC’s, platelets, most WBC’s as they’re too large to be pushed through the gaps in capillary wall
why is it not accurate to say that oxygen diffuses from the RBC’s into tissues?
-oxygen diffuses out of the RBC into the plasma
-the plasma moves by mass flow from capillary into tissue fluid that surrounds the tissue
why do plasma proteins stay in the blood
-too big to pass between the squamous cells of the capillary wall
why does the glomerulus in the kidneys have fenestrated capillaries
-areas where exchange occurs and larger molecules may need to enter or leave the blood
-fenestrated allow more rapid movement of molecules and allow larger molecules through
