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33 Cards in this Set

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The process by which the various organs and tissues of the body self-regulate blood delivery. Blood flow through individual organs is controlled intrinsically in response to local requirements.
autoregulation
Where does blood flow regulation occur?
capillary beds
Where does exchanges of materials take place between tissue cells and the blood?
true capillaries
What regulates the flow of blood into the true capillaries?
precapillary sphincter
The build-up of certain chemical signals in an area of the body can act as a metabolic control, bringing more blood to the capillaries of the area. What two types of blood vessels do these chemical signals affect and how do they work?
the feeder arterioles and precapillary sphincters
feeder arterioles dilate and help relax the precap. sphincters. If precap. sphincters are open, more blood will get through, but if closed less blood gets through.
Will the precapillary sphincters open or close in a capillary bed that is high in oxygen? Explain.
Close. If the oxygen levels in the tissue cells are already high, no more blood flow is needed in that area until the oxygen levels are lower again.
Will the precapillary sphincters open or close in a capillary bed that is high in carbon dioxide? Explain.
Open. Carbon dioxide is a metabolic waste product. If it builds up in a capillary bed, then the precapillary sphincters will open to allow it to be removed from the area.
Will the precapillary sphincters open or close in a capillary bed that has a high pH? Explain.
Close. Typically acids that accumulate must be removed from tissues. So when there is a low pH a lot of acid is present and the precapillary sphincters open.
Will the precapillary sphincters open or close in a capillary bed that is high in nutrients? Explain.
Close. If nutrients are already present in a capillary bed, precapillary sphincters will close. They open when nutrients are needed.
Why would a decreased blood pressure cause precapillary sphincters to open?
Decreased blood pressure will cause precapillary sphincters to open, allowing more blood to reach the capillary bed
List three ways materials move from the lumen of the capillary into the interstitial spaces.
1. Cytoplasmic vesicles
2. Fenestrations
3. Clefts
Pore in a capillary endothelial cell that may be open or covered by a delicate membrane; allows for freer passage of fluids and small solutes between capillaries and tissue cells.
fenestrations
How do clefts differ from fenestrations?
Clefts are gaps btwn the capillary endothelial cells, and fenestrations are part of capillary endothelial cells that may be open or have a thin membrane covering it.
Explain how materials are moved across an endothelial cell via bulk transport.
Through cytoplasmic vesicles.
Most solutes move across the capillary wall by diffusion. Define diffusion.
The movement of solutes from a region of higher concentration to lower concentration.
What types of solutes are able to diffuse though the plasma membranes of the endothelial cells from higher to lower concentration without the help of transport proteins or expenditure of metabolic energy. Give two specific examples.
Lipid soluble molecules
Oxygen & Carbon Dioxide
What types of solutes are typically transported from the blood to interstitial fluid by exocytosis and endocytosis across endothelial cells?
Lipophobic solutes
What types of solutes are typically transported from the blood to interstitial fluid through clefts or fenestrations? Give two specific examples.
Water soluble solutes
A.A's & sugars
What process is responsible for fluid leaving the capillaries at the arterial end and returning to the capillary at the venule end?
Bulk fluid flows
What happens if more fluid leaves the capillaries than is returned to the capillaries?
The fluid is returned to the bloodstream by lymph capillaries of the lymphatic system.
What two types of pressures influence fluid exchanges at capillary beds?
Hydrostatic
Osmotic
Is the pressure exerted by a fluid on the walls of its container.
hydrostatic pressure
What term is used to denote the blood pressure in the capillaries?
HPc
What happens to capillary hydrostatic pressure as the blood moves through a capillary bed? Explain.
HPc encounters friction in the cap, and thus HPc is lower at the venule end of cap.
What term is used to denote the pressure of the fluid in the interstitial fluid?
HPif
Why is the hydrostatic pressure of the interstitial fluid (HPif) normally low?
Because it is quickly picked up the lymphatic capillaries.
What is the net hydrostatic pressure in a capillary bed?
HPc-HPif = net NP
Predict the net movement of water (osmosis) across a membrane permeable only to
water in the following situations:

a. Higher concentration of solute
inside the sac compared to outside
the sac.

b. Higher concentration of solute
outside the sac compared to inside
the sac.

c. Equal concentrations of solute on both sides.
a. inside
b. outside
c. no movement
When you talk about osmotic pressure in a capillary bed, why is protein the only solute that is considered?
Becaue of its high content of plasma proteins leads to having high osmotic pressure.
Why is the osmotic pressure of the interstitial fluid typically very low?
Because the leak proteins are gathered up by the lymph caps very quickly.
What is the difference in the direction of force of net hydrostatic pressure and net osmotic pressure in a capillary bed?
HP forces fluid OUT of the capillary blood.
OP pulls fluid INTO capillary blood.
If net hydrostatic pressure is higher than net osmotic pressure, in which direction will fluid flow?
fluid leaves the capillary
If net hydrostatic pressure is lower than net osmotic pressure, in which direction will fluid flow?
fluid enters the capillary.