Microcirculation Flashcards
what is microcirculation?
characteristics of capillaries & lymphatic vessels
microcirculation lacks a ____
nerve supply (endothelial cells)
what is the only type of control that microcirculation has?
local control
where is microcirculation located?
connective tissue only
what is microcirculation composed of?
only squamous epithelial tissue (endothelium) with thin basal lamina
what are the 2 types of capillaries?
continuous
fenestrated
where are continuous capillaries located?
blood brain barrier, muscle, nervous tissue
(tight junctions, H2O should not leak out)
where are fenestrated capillaries located?
kidney & small intestine
(have holes, H2O can leak out)
which type of capillary has a higher filtration rate?
fenestrated
movement across the wall of the capillary & lymphatic vessels occurs by ____
diffusion
what substances move directly through the phospholipid bilayer?
gases (O2, CO2) & lipid soluble substances
what substances move through pores or at cell junctions?
ions & water
what factors increase diffusion?
- increased concentration gradient
- increased temperature
- increased surface area
- increased # of pores/channels
- decreased distance
lymph is a ___ pressure
negative (eg. -5mmHg)
“lymph sucks”
how would a decrease in plasma colloid osmotic pressure impact lymph flow?
increase lymph flow
capillaries in what organ have the lowest capillary permeability to plasma molecules?
brain
- continuous capillaries (tight junctions) only allow extremely small molecules such as water, O2, CO2 in/out of brain tissue
why does albumin have a slow rate of net movement across the capillary wall?
albumin is not lipid soluble
movement of solutes such as Na+ across the capillary walls occurs primarily by ____
diffusion
movement of water occurs by ____
bulk flow
what is bulk flow?
movement of water according to the balance between the pushing & pulling forces between the capillary & interstitial fluid
name the pushing forces of bulk flow
capillary (Pc) & interstitial (Pif) hydrostatic pressures
hydrostatic pressure is due to…
water pressure in the capillary or interstitial fluid
what increases hydrostatic pressure?
more volume due to larger diameter vessel or vasodilation
name the pulling forces
capillary (TTp) and interstitial (TTif) osmotic/oncotic pressures
what type of osmotic pressure do capillaries have and why?
plasma colloidal osmotic pressure due to albumin
the interstitial fluid osmotic/oncotic pressure is due to…
proteins in the IF such as collagen & elastin
in the kidney, the glomerulus is the ____, and the IF is termed ____
capillary
Bowman’s space
what type of capillary has a filtration coefficient?
very porous (eg. glomerulus)
how is the net filtration rate of porous capillaries determined?
filtration coefficient x bulk flow (net filtration pressure)
what does it mean when bulk flow is negative?
absorption: water moving IN to capillary
what does it mean when bulk flow is positive?
filtration: water moving OUT of capillary
what has the fastest net movement across capillary walls?
oxygen
where is there no interstitial fluid oncotic pressure?
glomerulus
when calculating bulk flow, what sign goes in front of capillary hydrostatic pressure?
+
when calculating bulk flow, what sign goes in front of interstitial fluid hydrostatic pressure?
-
when calculating bulk flow, what sign goes in front of interstitial fluid colloidal osmotic pressure?
+
when calculating bulk flow, what sign goes in front of colloidal osmotic pressure of plasma?
-
if interstitial fluid hydrostatic pressure increases, what happens to lymph flow?
increases
how is bulk flow calculated?
Pc - Pif + TTif - TTc
what would happen to capillary filtration rate if capillary water permeability decreased?
decreased filtration rate
what changes in microcirculation would occur with a decrease in the diameter of a precapillary arteriole?
decreased
- capillary filtration rate
- pressure
- volume
- conductance
increased:
- resistance
an increase in what factors would increase lymph flow?
increased capillary filtration rate & lymphatic pump activity
- increased hydraulic conductivity of capillary wall
- increased capillary hydrostatic pressure
- increased interstitial hydrostatic pressure
an increase in what pressures would decrease capillary filtration rate?
increased plasma colloid osmotic pressure
Increased IF hydrostatic pressure
a decrease in what factors would increase lymph flow?
plasma colloid osmotic pressure
an increase in what factors would increase capillary filtration rate?
increased capillary wall hydraulic conductivity (permeability to water)
