Lecture 5: Hemodynamics and Cappilary Exchange Flashcards
interstitial Fluid (ISF)
between and amng tissues
Arteriole
epithelial and smooth muscle
Oxygen and nutrients move
out of blood, across capilary wall, into ISF
CO2 and waste go opposite
total cappilaries in body:
60000 mines, SA of 5,000 cm 2
capilary sizes
about 1 mm long lumen about 8 micrometers just about the diameter of an RBC shorter distance is better every tisue cell usualy about 2-3 cell diameters from capillary (important for diffusion)
blood flow velocity in cap
0.1 cm/sec
slooooooow
conc or density of capilareises is
proportional to tissues metabolic activity
more active, more blood vessles
capillary bed
netwrok of caps
exchange takes place
entry into caps
sometimes controlled by 2 smooth muscle cells
Intercellular Clefts
pores
water and most small molecs can move through by diffusion
deep to tunica (lumen is superficial!)
Endothelial cell membranes
some small molecs and gases can pass through
oxygen concs: higer in BV lower in cells that use it
fenestrations
large molecs can pass through
little holes in cell
intnetnional holes al the way through cell
Continuous Capillaries
in lungs, skeletal muscle, CT
just gases move through, pretty sealed
formed by endothelial cells
Fenestrated Capillaries
kidneys, endocrine glands, small intestine
“little window”
Sinusoid (cappilary type)
liver, spleen, bone marrow, anterior pituitary gland
missing cells, giant caps
so free access to blood. BE CAREFUL!
liver: clotting factors
Spleen: purify blood (of infectious agents and old cells)
Random: BSA
albumin from class purpose: just to be in blood
Mechanisms of Fluid Exchange
2 mechs for blood to plass through cap walls
Passive or active
Diffusion
Passive
molecs and ions
movement form high conc to low conc
reach equlibrium
Bulk Flow
Passive
movement of fluid
high pressure to low pressure
Transcytosis
active
substances enter pinocytosis vesicles
move to endothelail cells (endocytosis)
exit opp side (exocytosis)
More on Bulk flow
fluid exchange between ISF and caps based on bulk flow 2 major fources to push OUT of caps BHP and IFOP 2 forces to pull fluid INTO capps
Blood Hydrostatic Pressure (BHP)
pushes fluid out through cap pores
Bulk Flow
push out
Interstitial Fluid Osmptic Pressure (IFOP)
pulls fluid out via osmosis
pressure small compared to BHP!
Bulk Flow
push out
Osmotic Pressure
fluid pressue due to water moving from high to low activity (conc)
Blood Colloid Osmotic Pressure (BCOP)
result of diff in proten concs between plasma and ISF
tends to pull water from ISF into caps
pull in
* suspension of protein in fluid: albumin
*big things in blood cant move across membrane are always there
*protein conc in blood different than in IFC
Interstital Fluid Hydrostatic Pressure (IFHP)
due to pressure exerted by ISF
normal very small!!!
pull in
Net Filtration Pressure
net movement of fluids driven by difference between inward and outward pressures
NFP=
(BHP + IFOP) - (BCOP +IFHP)
or
outward (filtration)- Inward (reabsorption)
Outward (respect to NFP)
filtration
Inward (Respect to NFP)
reabsorption
Negative NFP
fluid goes into blood (venous)
Positive NFP
fluid goes out of blood (probs arterial)
major factors that determine fluid movement across cap wall
BHP and BCOP
Filtration
result: constant flow of fluid washes over tissue cells at arterial end of capps
carries nutrients and oxygen with it
Reabsorption
result: return of fluid to capps at venous end
deposit wastes into venous system
Normal conditions fluid
slightly more fluid leaves than enters caps (3L/day)
Lymphatic vessles absorp excess fluid and return it to circulatory system
