Nordgren- The Peripheral Vasculature Flashcards
What is the purpose of the CV system?
To maintain INTERSTITIAL FLUID homeostais.
What is the Fisk principle?
Determines how substances are transported via blood bewteen the capillary bed in one location to another.
Where does passive diffusion often occur?
capillaries
What does diffusion depend on?
- concentration difference
- SA for exchange
- Diffusion distance
- permeability of capillary wall to the substance
Why are capillaries so efficient?
They maximize the area available for exchange while minimizing the distance to diffuse
The number of pores in the capillary depends on….
tissue location
ex. brain capillaries have FEW bores (tight)
What won’t cross a capillary wall?
Anything larger than 40 A (albumin)
Will a lipid soluble substance cross a membrane easily?
YES
b/c the membrane is only one cell thick
Net fluid OUT of a capillary =
filtration
Net fluid INTO a capillary=
resorption
Fluid flows in response to what two variables?
- Hydrostatic p (P)
2. oncotic pressure (pi)
What is hydrostatic pressure?
pressure of blood forcing fluid OUT of capillary
What is oncotic pressure?
osmotic attraction of water IN to regions of higher protein conentration
What is starling hypothesis?
Describes the relationship between opposing hydrostatic and oncotic forces on the net movment of transcapillary fluid (filtration or reabsorption)
What is the formula for the net filtration rate?
Net filtration rate = k (constant) {(hydrostatic pressure of intracapillary fluid- quantity of interstitial fluid)- (oncotic P of intracapillary fluid- quantity of intersitital fluid)}
What is filtration?
the net movement of solutes and fluid OUT of hte capillary and into the interstitial fluid
A POSITIVE pressure gradient is indicative of…
filtration
A NEGATIVE net pressure gradient is indicate of …
reabsorption
Why are the hydrostatic and oncotic pressures usually 0?
oncotic b/c very few proteins in IF
What occurs at the arteriole ned of a capillary?
filtration
What occurs at the venule end of a capillary?
reabsortpion
What does the release of histamine do?
INCREASES the capillary permeability to hte extent that proteins leak into the IF and LOWERS the oncotic pressure.
*exception to the oncotic P rule
What is the lymphatic system important?
keeps the interstitial protein concentration LOW and removes excess capillary filtrate from the tissues.
Why are lymphatic capillaries very porous?
Collect large particles and move them to lymph nodes then return fluid to the peripheral venous blood entering the right heart.
