Capillary Permeability Flashcards
capillary wall is composed of a
single layer of endothelial cells
what are two reasons for the efficient exchange of gases/nutrients in capillaries?
- Blood velocity is very slow: “sluggish” gives adequate time for exchange across the capillary membrane
- Huge surface area: over 10 million capillaries
Capillary permeability:
fastest blood velocity?
slowest blood velocity?
fastest: aorta
slowest: capillaries
Capillary permeability:
velocity is ______ proportional to the ______ ____
velocity is inversely proportional to cumulative area
velocity of blood flow =
V = F/A
V=velocity
F=flow rate
A=cross-sectional area of vessels
*velocity is inversely proportional to the cumulative area
hydrostatic pressure:
the force per unit area exerted on the wall of a blood vessel by the blood moving through it
slower flow promotes _______ & _______
greater gas and nutrient exchange
low pressure protects capillaries from ________
rupture
normal capillary BP is ______
low
*protects capillaries from rupture and promotes exchange
BP ______ as blood flow leaves the capillaries
lowers
hydrostatic pressure ____ as you move from the aorta to arteries then to arterioles, and so on…
decreases
at any time on ____% of circulating blood is in the capillaries
~5%
what percent of blood is considered the most important portion of blood volume and where is it located?
~5% in capillaries
where does O2 enter from capillaries?
interstitial fluid (IF)
where do CO2 and waste products enter from the tissues?
capillaries/bloodstream
virtually all gases, nutrients, metabolites, and water are continuously exchanged via…
capillary exchange
what is exchanged in “capillary exchange”?
gases
nutrients
metabolites
water
what is between the external interstitial fluid and plasma inside the capillary?
endothelial cells
*single layer
*semipermeable
T/F: capillaries have smooth muscle in their walls
FALSE
capillaries do NOT have smooth muscle in their walls
controlled by the large arterioles
*constricting their capillary sphincters
how do capillaries help in temperature regulation?
cool down via heat loss: vasodilation (increases blood flow)
warm-up via prevent heat loss: vasoconstriction (decreases blood flow)
how do capillaries respond to hot weather?
HEAT LOSS
vasodilation (increased blood flow)
cools down body
how do capillaries respond to cold weather?
PREVENT HEAT LOSS
vasoconstriction (decreased blood flow)
warms body up (bluish hands/feet)
if the precapillary sphincter is closed what happens?
precapillary sphincter closed =
blood flows only through the metarteriole and thoroughfare channel (center of the capillary)
not branching out to capillary bed
if the precapillary sphincter is open what happens?
precapillary sphincter open =
blood flows through capillary beds
study
how are exchangeable proteins moved across the capillary membrane?
vesicular transport
how are small water-soluble substances moved across the capillary membrane?
through intercellular clefts (bulk flow)
how are lipid-soluble substances moved across the capillary membrane?
diffusion through endothelial cells (semipermeable membrane)
*concentration gradient
O2, CO2
what are lipid-soluble substances of capillary permeability?
O2
CO2
three modes of transport for substances to pass through capillaries?
- Diffusion - no energy required (O2, CO2)
- Intercellular cleft (water-soluble)
- Vesicular transport (large proteins)
What are some factors that affect the rate of diffusion in capillaries?
high temperatures (faster)
low temperatures (slower)
higher concentration gradient (faster)
lower concentration gradient (slower)
small solutes (faster)
large solutes (slower)
viscous solutions (slower)
What is the term for endocytosis to exocytosis in capillary permeability?
vesicular transcytosis
vesicular transport is the translocation of _____ macromolecules in vesicles
impermeable (like large solutes, proteins, antibodies)
*requires energy ATP
what is “bulk flow “of capillary transport?
how smaller water-soluble solutes move across the capillary wall
what capillary types affect bulk flow? ranked
continuous capillaries: least flow
fenestrated capillaries: more flow
discontinuous capillaries: most flow
Starling Forces of capillary Bulk Flow
Filtration: bulk flow of solutes move from bloodstream to interstitial fluid
Reabsorption: bulk flow of solutes from interstitial fluid to bloodstream
what forces impact Filtration (Starling Forces of capillaries)?
capillary hydrostatic pressure
interstitial fluid osmotic pressure
*blood stream to interstitial fluid
what forces impact Reabsortion (Starling Forces of capillaries)?
capillary oncotic pressure “colloid osmotic pressure”
interstitial fluid hydrostatic pressure
*bloodstream to interstitial fluid
Starling’s Law equation in words
Starling’s Law equation
NFP= net filtration pressure
HPc= capillary hydrostatic pressure
HPif= interstitial fluid hydrostatic pressure
OPc= capillary oncotic pressure
OPif= interstitial fluid osmotic pressure
Capillary Ontotic Pressure aka Colloid osmotic pressure: osmotic pressure exerted primarily by _______
impermeable plasma proteins
capillary hydrostatic pressure is …
the froce directed out of the capillary by fluid pushing against the capillary
hydrostatic pressure in capillaries moves fluid ____ of capillary
out
osmotic pressure in capillaries moves fluid ____ capillary
into
hydrostatic pressure in interstitial fluid moves fluid ____ capillaries
into
osmotic pressure in interstitial fluid moves fluid ____ of capillaries
out
Where are plasma fluids filtered out of a capillary?
Whare are plasma fluids reabsorbed in a capillary?
filtered out: capillary’s arteriolar end (~20L/day)
reabsorbed: venous end (~17L/day)
the fluid that remains in the interstitial space becomes part of the interstitial fluid and is then removed by the _____
lymphatic system (~3L/day)
what goes through the three modes of transport of capillary exchange?
- diffusion: lipid-soluble O2/CO2
- Vesicular transport: large proteins insulin/IgA
- Bulk Flow (convection): water-soluble, plasma/IF/electrolytes/ions/glucose/amino acids
trace of the capillary system from arteries to veins
arteries
arterioles
capillaries
venules
veins
what are anastomoses?
a point where two blood vessels merge
can serve as a bypass connection between vessels
*no capillary beds
the primary function of the lymphatic system
lymphatic system: move fluid/lymph directionally towards the heart (one way)
return excess lymph fluid to heart and helps large molecules (hormones/lipids) enter the blood
lymphatic capillaries have relatively _______
low pressure
blood capillaries vs lymphatic capillaries
blood:
high pressure
narrow
reddish
lymphatic:
low pressure
wide
colorless
potential causes of edema
- increased capillary blood pressure
- decreases plasma colloid osmotic (oncotic) pressure
- increased capillary permeability
- obstruction/disruption of lymphatics (lymphedema)
edema: increased capillary blood pressure is due to…
increased plasma volume
increased venous pressure
arteriolar dilation
edema: decreased plasma colloid osmotic (oncotic) pressure is due to…
decrease plasma albumin/large plasma proteins
edema: increased capillary permeability is due to…
filtration of proteins into interstitial space
increase in interstitial oncotic pressure
*increased interstitial fluid exceeds the lymphatic systems compensatory return
lymphedema?
swelling of body parts (distal limbs)
unable to return access fluids to the venous blood supply
buildup of fluids in lymphatics and interstitial tissue
lymphostatic fibrosis?
process of built-up fluid in limbs hardens (permanent scarring)
