Human Phys 4.3 Flashcards
Microcirculation
Vessels form the first order arteriole to the first order venule
What does microcirculation do in most tissues?
Serves nutritional needs
What are some of the non nutritional needs in microcirculation?
Filtration
Temperature regulation
Signaling and host defense
What is the role of sphincters on capillaries?
Contract to increase resistance (helps blood flow only where it is needed)
What are endothelial cells held together by?
Tight junctions
What is the most predominant capillary?
Continuous capillary
Where are continuous capillaries located?
Skeletal muscle, in BBB no interendothelial junctions due to narrow tight junctions (low permeability)
Where are fenestrated capillaries located?
Small intestine (middle permeability)
Where are sinusoidal capillaries (discontinuous) located?
Liver (high permeability)
What do lipid soluble substances do?
Diffuse directly through the cell membranes of the capillary endothelium
How do lipid insoluble cross the capillaries?
Via the intercellular clefts
How does the permeability of the capillary pores vary?
According to the diameter of the cleft and size of the molecule
How many capillaries are perused at rest in the skeletal muscles?
20% (most become active during exercise)
What does PO2 within the capillary depend on?
Concentration of free O2
O2 content of blood
Capillary blood flow
Capillary radius
Radius of tissue cylinder
O2 consumption of surrounding tissues
Axial distance along the capillary
What is the space between cells called?
Interstitium
