Unit 4 -Vasculature: Microcirculation, lymphatics, and Veins Flashcards
What are the four types of capillaries?
Continuous capillaries, fenestrated capillaries, sinusoids (discontinuous capillaries), and lymphatic capillaries
What are is the most common type of capillaries?
continuous capillaries
What is the structure of continuous capillaries?
made up of tight junctions with no pinocytotic vesicles or clefts
What is the function of continuous capillaries?
they carry proteins for amino acids and glucose
Where are fenestrated capillaries located?
in the GI tract/intestine, kidney, and endocrine pancreas
Where are the fenestrations of fenestrated capillaries located?
in the capillary wall
What is the function of fenestrated capillaries?
they allow rapid exchange of large molecules and fluid
What is the structure of sinusoids?
they have large clefts and fenestrae and a discontinuous basal lamina layer
Where are sinusoid capillaries located?
in the liver, spleen, lymphoid organs and bone marrow
What is the function of sinusoid capillaries?
they allow rapid exchange of larger molecules, particles, whole cells, and fluid between the blood and interstitium
What is the structure of lymphatic capillaries?
the endothelium overlaps in places, there are no tight junctions, it has intercellular clefts
What are lymphatic capillaries supported by?
anchoring filaments
What is the function of lymphatic capillaries?
they pull away fluid to keep the interstitium dry so that filtration can continuously occur
What does bulk flow occur through?
capillary pores
What influences bulk flow?
hydrostatic pressure
What does fluid movement across the capillary membrane depend on?
the sum of osmotic pressure and hydrostatic pressure across the membrane
Where is fluid filtered and where is it absorbed?
it is filtered at the arteriole end and absorbed at the venous end
What is the Starling equation?
Kf(Pc-Pi)-(πc - πi)
What does Pc in the starling equation stand for?
capillary hydrostatic pressure
What does Pi in the starling equation stand for?
interstitial hydrostatic pressure
What does πc in the starling equation stand for?
capillary oncotic pressure
What does πi in the starling equation stand for?
interstitial oncotic pressure
What does causes interstitial edema?
increase in capillary hydrostatic pressure
decrease in capillary oncotic pressure
increase in capillary permeability
decrease in lymphatic flow
What is the function of lymphatics?
drain excess fluid from interstitial space, removing excess interstitial protein and returning it back into circulation, and removing particles and bacteria into the blood system
