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20 Cards in this Set

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  • Back
What is located at the junction between arterioles and capillaries?
Precapillary sphincter
Do capillaries contain smooth muscle?
No.
What are capillaries composed of?
Single layer of endothelial cells and a surrounding basement membrane.
How do small water soluble substances enter capillaries?
Through pores(clefts) between adjacent endothelial cells.
Can proteins fit through the pores?
Not normally, they are too large.
Where are the pores the tightest?
In the brain, where they form the blood brain barrier.
What are the components of the blood brain barrier?
Endothelial cells of the cerebral capillaries
Choroid plexus epithelium.
What substances pass readily through the barrier/
Lipid soluble substances.
What substances are excluded by the barrier?
Protein and cholesterol.
What are the functions of the blood brain barrier?
1. Maintains a constant environment for the neurons in the CNS.
2. Protects the brain from toxic substances
3. Prevents movement of neurotransmitter into the circulation.
Indicate where the following substances are found in higher concentrations. In the blood or the CSF?
Ca+
Cholesterol
Cl-
Creatinine
Glucose
HCO3-
K+
Mg+
Na+
Protein
Ca+-Blood
Cholesterol-Blood(absent in CSF)
Cl- Equal in both
Creatinine-CSF
Glucose-Blood
HCO3- Equal in both
K+-Blood
Mg+2-CSF
Na+-Equal in both
Protein-Blood(absent in CSF)
Where are the pores the widest?
In the liver and intestine(sinusoids)
What is unique about the junctions in the sinusoids?
They are wide enough to allow the passage of proteins.
How do large water soluble substances enter capillaries?
Pinocytosis.
How do lipid soluble substances enter capillaries?
Through the membrane of the endothelial cells by simple diffusion.
What is lymph?
The excess fluid that is filtered out of capillaries that is not reabsorbed.
What is the function of lymph?
To return the lost fluid along with any filtered proteins back into circulation.
What type of flow do the lymphatics demonstarte?
Unidirectional
What permits this type of flow?
One way flap valves.
What causes edema?
There is more interstitial fluid than the lymphatics can return into the circulation.