Microcirculation Flashcards
What are metaarterioles?
They are thoroughfare vessels that go stratight from the arterioles to the venule, bypassing the capillary bed altogether
What regulates flow through capillaries?
Neural and metabolic mechanisms that can control the precapillary sphincters
Do capillaries have muscles?
No, but there are precapillary sphincters where the capillary comes off the arteriole that can close off the capillary
If blood flows through a metarteriole and bypasses a capillary bed, is there exchange of gas/waste products?
No
What is the difference between the arteriolar radius and the precapillary sphincters when it comes to regulating blood flow?
The arteriolar radius determines the overall blood flow to a particular capillary bed
The capillary sphincters determine which capillaries are perfsued
What are the 3 types of capillaries?
Continuous
Fenestrated
Discontinuous
What are continuous capillaries?
Capillaries that have tiny clefts between each endothelial cell to allow hydrophilic molecules to pass through
(Found in muscle, skin, lung, and brain)
What are fenestrated capillaries?
Capillaries that have fenestrae which are like “windows” in the cell membranes of each cell to allow water and small hydrophilic molecules to pass
(Found in kidneys, intestine, endocrine glands)
What are discontinuous capillaries?
Capillaries that have wide gaps between adjacent endothelial cells to allow large molecules and water to pass through
(Found in liver, bone marrow, spleen)
How do lipophilic molecules get through the capillary cells?
They diffuse right through the plasma membranes
Does albumin easily leak out the capillaries?
No, proteins are usually too large to diffuse through
What is filtration?
Movement of fluid OUT of the capillary and into the intersitium
What is absorption?
Movement of fluid INTO the capillary from the interstitial space
What are the 4 starling forces that affect capillary fluid movement?
- Capillary hydrostatic pressure
- Interstitial fluid hydrostatic pressure
- Plasma oncotic pressure
- Interstitial oncotic pressure
Does capillary hydroststic pressure favor filtration or absorption
Filtration