PSIO202 Exam 1 Lecture 5 Flashcards
When things cross through the capillary wall, what is on the “other side” from the capillary?
ISF (interstitial fluid)
How do oxygen, nutrients, waste, and CO2 move through the capillary (direction)?
oxygen and nutrients move out of the capillary into the ISF, waste and CO2 move into the capillary from the ISF
What is a capillary bed?
network of capillaries where exchange of material with the tissue cell can take place
How close are tissue cells to capillaries?
All cells are within 2-3 cells from a capillary
What are the dimensions of the capillary? Length, diameter, and velocity of flow?
Length: 1 mm
Diameter: 0.8 micrometers
Velocity: 0.1 cm/sec
What determines if a tissue has more or less capillaries?
Metabolic activity - more metabolic activity needs more capillaries
If capillaries are so small, why does bloodflow slow down so much in them?
The cross sectional area is huge, so there is still more space for the blood even though individual capillaries are tiny.
What are the three structures that allow passage of things through a capillary? What do they allow to pass?
intercellular clefts (lines between): water and water soluble solutes
endothelial cell membranes: small molecules and gases
fenestrations (holes, pores): large molecules
What are the structures like in a continuous capillary? What passes through them, and where are they located?
They have tight junctions between the endothelial cells, but small molecules and gases can still pass through the intercellular celfts. Located in the lungs, skeletal muscle, and connective tissues.
What are the structures like in a fenestrated capillary? What passes through them, and where are they located?
They have pores in the endothelial cells which allow more small molecules to pass. Located in the kidneys, endocrine glands, and small intestine.
What are the structures like in a sinusoid capillary? What passes through them, and where are they located?
Big fenestrations, few tight junctions, and wide clefts allow for large molecules like proteins or whole cells to pass through. Located in the liver, spleen, bone marrow, and pituitary gland.
What is diffusion? Passive or active?
movement from high concentration to low concentration, passive
What is bulk flow? Passive or active?
Passive process. Movement from high pressure to low pressure.
What is transcytosis? Passive or active?
Active, vesicles endocytose then exocytose on the other side
What forces are involved in bulk flow?
BHP, IFOP, BCOP, and IFHP
What is BHP? Reabsorption or filtration pressure?
pushes fluid out through the capillary pores, filtration
What is IFOP? Reabsorption or filtration pressure?
Pulls fluid out of the capillary via osmosis. Filtration.
What is BCOP? Reabsorption or filtration pressure?
Difference in protein concentration between plasma and ISF that pulls water into the capillary since the proteins can’t get out. Reabsorption.
What is IFHP? Reabsorption or filtration?
The pressure of ISF favors movement into capillaries. Reabsorption.
Which of the 4 pressures significantly contribute to NFP, vs the ones that are very small?
BHP and BCOP contribute, but IFOP and IFHP are very small.
What is the equation for NFP? What is the meaning of it?
NFP is the net movement of fluid (positive is movement out, negative is movement in)
NFP= (BHP+IFOP) - (BCOP+IFHP)
How does albumin impact capillary pressures?
Albumin cant move out of the capillary, Na+ is attracted to albumin and moves in too, water needs to move in to balance the Na+ (maintains BCOP)
Does more fluid filter or reabsorb from/to capillaries? How much?
More filters out than comes back in. 20 L out, 17 L back.
What is the role of filtration from the capillaires?
Constant wash of fluid over cells that brings nutrients and oxygen
What is the role of reabsorption into the capillaries?
Return of fluid brings waste and CO2 into the venous blood
How does the NFP differ at the arterial and venous end of a capillary? Why does this make sense?
venous: negative NFP (movement in) to bring wastes back to the veins
arterial: positive NFP (movement out) to take the nutrients and oxygen out to the cells
