Flashcards in Capillaries Deck (65):
What is the function of the capillaries?
Exchange fluid, nutrients, hormones etc
What is the rate of exchange of nutrients in capillaries related to?
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?
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?
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?
pCO2, pH, flow
What is the main metabolic regulator of the brain? Lesser regulators?
What is the main metabolic regulator of the heart? Lesser regulators?
pO2, pCO2, pH
How does epinephrine control blood flow through capillaries?
Constricts and dilates
How does Norepinephrine control blood flow through capillaries?
How does dopamine control blood flow through capillaries?
Constricts and dilates
How does histamine control blood flow through capillaries?
How does acetylcholine control blood flow through capillaries?
How does angiotensin II control blood flow through capillaries?
How do Kinins control blood flow through capillaries?
How does ADH/vasopressin control blood flow through capillaries?
How does VIP control blood flow through capillaries?
How do hormones have opposite effects on the same capillary bed?
How does adenosine control blood flow through capillaries?
How does hypoxemia control blood flow through capillaries?
How does [H+] and [K+] control blood flow through capillaries?
How does hypercapnia control blood flow through capillaries?
How do Kreb cycle intermediaes control blood flow through capillaries?
How does endothelin control blood flow through capillaries?
How does EDRF (NO) control blood flow through capillaries?
What determines that rate of exchange of a chemical through a capillary bed?
Solubility in lipids or water
If a chemical is lipid soluble, how does it pass through capillaries?
If a chemical is water soluble, how does is pass through the capillary bed?
How does molecular size relate to the rate of passage through capillaries?
What is colloid osmotic pressure?
The force exerted by molecules inside a fluid on the wall that contain it
What is capillary hydrostatic pressure (Pc)? How does it relate to flow?
Fluid pressure within capillaries that tends to move fluid out
Directly related to flow
The hydrostatic pressure of tissues is (high/low) compared to capillaires? How does this affect permeability?
A tightly encapsulated tissue (like the kidney) causes what?
Increases Pif, to move fluid back into tissue
Oncotic pressure within capillaries tend to move fluid (in/out).
Proteins in the interstitium will move fluid (in/out) of the capillaries?
What is the equation for net pressure?
Pc - Pif -(pi)c + (pi)if
If net fluid pressure is greater than 0, where will fluid move?
out of the capillary
If net fluid pressure is less than 0, where will fluid move?
Into the capillary
How do water soluble substances get through the capillaries?
Through the pores in the capillaries
How do we describe flow through capillaries (individually or as a sum/product of many?)
Sum of many capillaries
Where in the body is the only place dopamine will cause capillary constriction?
What is the effect of adenosine in the kidneys?
Constriction of capillary beds
What does reabsorption mean in terms of capillary exchange?
Reuptake into the capillary
What does filtration mean in terms of capillary exchange?
Removal from the blood
How permeable it the liver to molecules? The brain?
Liver = highly permeable
Brain = Not so much
What maintains the low hydrostatic pressure in the interstitium?
What is the effect on interstitial hydrostatic pressure if the tissue is surrounded by a tight capsule? What is the effect that this produces on the flow of interstitial fluid (does it go back in, or does it come out faster)?
Increases it, causing fluid to move back into the capillary
What is oncotic pressure? What is the effect on movement of fluid into/out of capillaries?
The pressure exerted by a [C] of some molecule. This causes movement in the direction of higher [C]
What is the equation for the net pressure exerted on capillary fluid? What happens if this sum is greater than 0?
Pc - Pif - (pi)c + (pi)if
If this sum is >0, then net fluid movement will be out of the capillary
In the equation of net pressure in a capillary (Pc - Pif - (pi)c + (pi)if), which component is variable with the location in the capillary?
What happens if there is in an increase of Pc?
A shift of the curve, meaning that at every point in the capillary, there is a higher rate of filtration
What happens if there is decrease in oncotic pressure within the capillary?
Shift of the horizontal line downward, meaning that at every point in the capillary, there is a higher rate of filtration
What happens to Pc if we decrease resistance within the capillary (say, by opening a sphincter at the venule end of the capillary)?
Pc curve shifts down, meaning that at every point along the capillary, there is less filtration occurring
Which variables does the lymphatic system change, so that there is a net efflux of fluid out of the capillaries?
(pi)if and Pif (both are decreased)
What are the three factors mentioned in class, that can serve to increase the Pc? What will this cause?
Standing, Heart failure, venous thrombus
These all cause edema
What are the three factors mentioned in class, that can serve to decreased the (pi)c? What will this cause?
Nephrotic syndrome, starvation, pregnancy