Capillaries Flashcards
What is the function of the capillaries?
Exchange fluid, nutrients, hormones etc
What is the rate of exchange of nutrients in capillaries related to?
Bulk flow
What features of the capillaries contribute to its function?
Thin walls with pores
What modifies what goes through capillaries?
Size of the pores
Can lipid soluble substances get through capillaries via diffusion? Can proteins? Water soluble ions?
Yes for lipid
No for proteins or water solubles
What are the spaces between the capillaries?
Intracellular clefts and caveolae
What covers the tissue side of the capillaries?
BM
What is vasomotion?
intermittent blood flow through capillaries d/t contraction of metarterioles and precapillary sphincters
What structures regulate blood flow through capillaries? What are those regulated by?
Through precapillary sphincters
Regulated by tissue oxygen usage
Is there smooth muscle in capillaries? What is the consequence of this?
No, means that can close capillaries completely
If you increase surface area (as in the increase CSA for capillaries) what happens to velocity?
Decreases velocity
Why can’t capillaries contract or relax?
No smooth muscle
Blood flow through capillaries depends on what?
What can get through upstream via sphincters, arterioles etc
What is the main metabolic regulator of skeletal muscle? Lesser regulators?
pO2
pCO2, pH, flow
What is the main metabolic regulator of the brain? Lesser regulators?
pCO2
pO2, adenosine
What is the main metabolic regulator of the heart? Lesser regulators?
[adenosine]
pO2, pCO2, pH
How does epinephrine control blood flow through capillaries?
Constricts and dilates
How does Norepinephrine control blood flow through capillaries?
Constricts
How does dopamine control blood flow through capillaries?
Constricts and dilates
How does histamine control blood flow through capillaries?
dilates
How does acetylcholine control blood flow through capillaries?
Dilates
How does angiotensin II control blood flow through capillaries?
Dilates
How do Kinins control blood flow through capillaries?
Dilates
How does ADH/vasopressin control blood flow through capillaries?
Constricts
How does VIP control blood flow through capillaries?
Dilates
How do hormones have opposite effects on the same capillary bed?
Different receptors