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20 Cards in this Set
- Front
- Back
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What is located at the junction between arterioles and capillaries?
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Precapillary sphincter
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Do capillaries contain smooth muscle?
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No.
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What are capillaries composed of?
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Single layer of endothelial cells and a surrounding basement membrane.
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How do small water soluble substances enter capillaries?
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Through pores(clefts) between adjacent endothelial cells.
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Can proteins fit through the pores?
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Not normally, they are too large.
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Where are the pores the tightest?
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In the brain, where they form the blood brain barrier.
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What are the components of the blood brain barrier?
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Endothelial cells of the cerebral capillaries
Choroid plexus epithelium. |
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What substances pass readily through the barrier/
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Lipid soluble substances.
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What substances are excluded by the barrier?
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Protein and cholesterol.
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What are the functions of the blood brain barrier?
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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. |
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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) |
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Where are the pores the widest?
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In the liver and intestine(sinusoids)
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What is unique about the junctions in the sinusoids?
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They are wide enough to allow the passage of proteins.
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How do large water soluble substances enter capillaries?
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Pinocytosis.
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How do lipid soluble substances enter capillaries?
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Through the membrane of the endothelial cells by simple diffusion.
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What is lymph?
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The excess fluid that is filtered out of capillaries that is not reabsorbed.
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What is the function of lymph?
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To return the lost fluid along with any filtered proteins back into circulation.
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What type of flow do the lymphatics demonstarte?
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Unidirectional
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What permits this type of flow?
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One way flap valves.
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What causes edema?
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There is more interstitial fluid than the lymphatics can return into the circulation.
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