microcirculation (midterm 2) Flashcards
what is microcirculation the site of
nutrient transport at the capillaries
what is the total surface area of the 10 billion capillaries
500-700 m^2
how far are most cells from a capillary
20-30 um
what is the structure of microcirculation
artery (branches 6-8 times)->arterioles (branch 2-5 times)->capillaries
what are precapillary sphincters
regulate the opening and closing of capillaries
how is the capillary wall formed
from a unicellular layer of endothelial cells surrounded by a basement membrane
what does the capillary wall contain
intercellular clefts - allows fluid transport between endothelial cells
what is the blood-brain barrier
brain capillaries have tight junctions that tightly regulate transport
why do kidneys allow regulated transport
they contain fenestrae
are liver capillaries open
very open, allowing free transport
how fast does water diffuse through the capillary
80x faster than the rate of plasma flow
what is brownian motion
nutrient exchange from the capillary to the interstitial fluid (dominated by passive diffusion)
what is interstitium
space between cells containing interstitial fluid
what are the structural components of interstitium
- collagen fibers bundles (provide tensile strength)
- proteoglycan filaments
what is interstitial “gel” fluid
hydrogel form of tissue (~99% diffusion rate of free fluid)
what is intertitial “free” fluid
water based form of tissue - less than 1% of tissue volume
what are the four forces that affect the movement of fluid between capillaries and interstitial spaces
capillary pressure (Pc)
interstitial fluid pressure (Pif)
plasma osmotic pressure (“pi”p)
interstitial fluid osmotic pressure (“pi”if)
what do the fluid exchange forces do
capillary pressure (Pc) - pushes fluid out of cap (+)
interstitial fluid pressure (Pif) - pushes fluid in capillary (+)
plasma osmotic pressure (“pi”p) - pushes fluid in capillary (+)
interstitial fluid osmotic pressure (“pi”if) - pushes fluid out of capillary (+)
what is arterial blood flow driven by
pressure (venous end is not)
what is starling equilibrium
amount of fluid filtering outward from some capillaries = amount of fluid that is returned to the circulation by absorption through other capillaries
what is the lymphatic system
route where fluid can flow from the interstitial spaces into the blood (where excess fluid drains into)
what do liver, intestinal lymphs, and body lymphs carry proteins at
6 gm/dl
3-4 gm/dl
3-5 gm/dl
