Peripheral Circulation: Exchange Vessels Flashcards
What are metarterioles?
Arterio-venous shunt vessels
What is true about precapillary sphincters?
They have no autonomic innervation
What makes it difficult for non-lipid substances to penetrate capillary walls?
Tight intercellular junctions between capillary cells
What are fenestrated capillaries?
Capillaries with small holes and a basement membrane; glycocalyx covers the holes
What are discontinuous/sinusoidal capillaries?
Capillaries with large holes and no basement membrane
What occurs in heart failure due to high central venous pressure?
Sinusoidal capillaries in the liver have large fluid exudates causing ascites
What is Gibbs-Donnan Equilibrium?
An impermeable anion hinders cation diffusion
What is Fick’s Law?
Flux of solute=Permeability coefficient of x times the conc. difference of x in capillary bed and interstitial fluid
What occurs to diffusion distance when additional capillaries are opened?
Diffusion distance decreases
Extraction ratio:
[O2]art-[O2]ven/[O2]art=%
What is bulk flow?
If solutes are transported with the fluid
What force dominates in the arteriole end of the capillary?
Hydrostatic pressure
What force dominates in the venous end of the capillary?
Osmotic pressure
What do the values of Jv tell you?
Positive= filtration Negative= absorption
What is the equation for transcapillary exchange?
Jv = (Pc - Pif) - (pi c - pi if)
Cap hydrostatic - tissue hydrostatic) - (Cap osmotic - Tissue osmotic
