Regulation of Interstitial Fluid Volume Flashcards
Interstitial fluid flow
microvascular filtration -> Interstitial space -> lymph flow -> circulatory system
microvascular filtration -> Interstitial space -> serosal transudation -> lymph flow -> circulatory system
Interstitial Space
b/n vascular space & cells. contains interstitial fluid and extracellular matrix (collagen, elastin, hyaluronan & glyocsaminoglycans)
a gel w/ small free fluid channels
In most capillary beds under normal conditions,
reabsorption does not occur
Interstitial Fluid Pressure
Sub-atmospheric (in many tissues like lung, subq tissue, resting sk. m.)
~occurs because of active fluid drainage
Supra-atmospheric (heart, liver, kidney, contracting sk. m)
~always helps drive fluid out of tissue
Interstitial Protein concentrations
Thoracic duct ~75%
Liver ~100%
CNS ~1%
Full complement of clotting factors
Sum interstitial protein > sum of plasma protein
Pressure-Interstitial Volume Relationship
depends on the tissue:
-lung & subq tissue = low volume, low P
-heart & kidney = high volume, high P
(directly related!)
When does interstitial P ^?
as interstitial volume ^
How does an increase in venous pressure reduce microvascular filtration?
^ venous P drives fluid into interstitial space => ^ interstitial V => ^ interstitial P => reduced filtration because the hydrostatic and colloid P difference is less.
the ^ interstitial P brings filtration back towards normal but at a higher interstitial V.
Anti-edema Mechanisms
- Increased interstitial fluid P
- Increased lymph flow (10x or more)
- Decreased intersitial COP via protein wash-down & ^ lymph flow
- Increased serosal transduation
How does increased interstitial P reduce edema?
it enhances fluid removal
Lymphatic vessel structure
-endothelium, basement membrane, little bit of sm. m., one-way valves, perfused & innervated (large ones)
Lymphatic vessels act as pumps b/c of
their one-way valves & sm. m.
How does Load-Dependence of the heart work?
contractions ^ strength => ^ stroke volume => ^ freq. of contraction => ^ flow
Lymphatic Response to increased Atrial P
increases lymph flow significantly
Microvascular protein flow =
protein flow into interstitial space
Protein Washdown
When fluid filtration increases, total protein increases b/c of diffusion but protein concentration decreases.
Net effect of Protein Washdown
decrease in interstitial protein concentration
Interstitial Protein Concentration vs. Microvascular Filtration
inversely proportional.
high interstitial [protein] = low filtration rate
low interstitial [protein] = high filtration rate
What happens if edema happens again and the anti-edema mechanisms are already taking place?
edemas would suddenly start popping up everywhere.
to help: give colloid solution or give hypertonic saline
Anti-edema mechanisms purpose
to help reduce likelihood of edema
Serosal Transudation
flow from interstitial space across serosal surface to surrounding cavity
When does transerosal flow increase?
with edema formation
Potential Space drainage
- occurs via lymphatic system
- lymphatic stomata (how it goes away)
- doesn’t filter across a membrane
- not reabsorbed into the vascular space
All anti-edema mechanisms are
interconnected!
