Taylor- Microcirculation Flashcards
2 main things the microcirculation regulates
solute and fluid transport
regulate blood flow into tissues
Arterioles
regulate # of perfused capillaries
Pre-capillary sphincters
sites for exchange
capillaries and post-capillary venules
route of exchange through inter-endothelial cell clefts
paracellular
route of exchange through vesicular transport or directly through cell (including fenestrae)
Transcellular
route for exchange depends on 2 things
type of endothelium
transported substance
small solutes (gases, FA’s)
steroid and thyroid hormones
lipid soluble
small solutes (electrolytes, glucose)
Albumin (protein)
hydrophillic
becomes an osmotic force that pulls water into vessel when this substance is trapped inside vessel
Albumin
Transendothelial diffusion of small solutes (flux of solute); O2 leaving blood to supply tissues (specifc organ)
Js
what does the diffusion of small solutes (Js) really depend on
solute concentration gradient
(O2 will flow out, CO2 will flow in)
the smaller the diffusion distance (delta x) =
greater flux of solute (Js)
what happens if you increase concentration of solutes
increase their concentration gradient
what happens if you increase the solutes’ utilization in the tissues (increasing the area for exchange)
increase their concentration
opening what will increase the # of perfused capillaries, increasing the area for exchange
precapillary sphincters
transendothelial fluid movement
Jv
explain the picture
Pc - Pif is hydrostatic pressure
pi p - pi if is osmotic pressure
these two oppose each other
equation that describes fluid movement (net water exchange)
Starling equation
Jv is positive means what
filtration is happening (movement out of capillary)
Jv is negative means what
absorption (movement into capillary)
when Net Filtration Pressure (NFP) is positive
fluid is filtered into tissue
when Net Filtration Pressure (NFP) is negative
fluid is absorbed from tissue to blood
discontinuous capillary (very leaky) seen where
liver bed
continuous fenestrated capillaries seen where
mesenteric bed
continuous- unfenestrated capillary seen where
brain
NFP + in resting skeletal muscle
filtering
NFP - in the brain
absorbing
change in local arteriolar tone alters what
NFP
arteriolar dilation does what to NFP (filtration pressure)
increases
arteriole constriction does what to NFP (filtration pressure)
decreases
net flux at capillaries (Jv) is filtering while ____ are taking up that fluid and protein
lymphatics
lymphatics all come together and dump into _______ returning stuff back to venous circulation
subclavian veins
when filtration exceeds lymph flow (fluid accumulates in interstitial space)
edema
fluid in abdomen
ascites
deals w/ both hydrostatic and osmotic gradients; too much intravascular pressure or dilution of plasma proteins (low albumin)
Hydrostatic edema
increased endothelial “leak”
permeability edema
limitation in lymphatic drainage
lymphedema
this is common w/ R sided heart failure
Hydrostatic edema
signs of this include pitting edema around feet and ankles
heart failure
high systemic capillary pressure increases______
filtration
high pressure where leads to fluid in abdominal cavity (ascites)
liver sinusoids
pulmonary edema
high pulmonary capillary pressure leads to increased ______
fluid filtration in the lungs (pulmonary edema)
promotes increased filtration and edema due to osmotic pressure decrease (decreased albumin)
hypoproteinemia
associated w/ myxedema
hypothyroidism
overproduction of ECM proteins; proteins pull water towards them in interstitial space
Myxedema
Myxedema
more filtration due to disruption of microvascular barrier
permeability edema
one of the main injuries causing permeability edema
burns
lymphatic disruption or obstruction (at lymph flow, not capillary)
Lymphedema
impacts perfusion and diffusion (compresses circulation and make exchange harder)
edema
painful pressure increase in muscle after damage; if edema is bad enough to restrict blood flow, pain and ischemia
Compartment Syndrome
flux of solutes (Js) increases across endothelial barrier 3 ways:
- opening of precapillary sphincters
- conc. gradient of solutes
- reduced diffusion distance
flux of fluid across endothelial barrier into tissues increases with: (2 things)
- increased hydrostatic pressure gradient (capillary pressure)
- decreased osmotic pressure gradient (albumin)
