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17 Cards in this Set

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From the flow equation, what is the critical consideration for epithelial flow?
In this case, area. Think about it.
What are the two trans-epithelial routes?
Paracellular and transcellular. Transcellular is modulated by the presence or absence of certain transporters in either the apical or basal membranes.
What are the three mechanisms of trans-epithelial flow?
1. Lipid solubility.
2. Membrane transport proteins
3. Exo/Endo cytosis.
How does a cell maintain it's electrically negative state?
1. Na/K/ATP-ase develops ion gradients using chemical processes converted to electrical differences.
2. K channel generates negative Em.
**What is the point of all chemical and electrical activity?
1. VOLUME IS MOVED ELECTRICALLY
2. MEMBRANE POTENTIAL IS MODULATED VIA MOVEMENT.
3. KEEP OSMOTIC PRESSURE HAPPY.
Is Na absorbed or secreted?
Na is absorbed from the luminal side and ejected on the basal side.
Why is the entry for Na a channel and the exit an active transporter?
The cell is more negative than the lumen, so Na enters easily. Kicking it back out requires effort.
What does Na bring with it through a cell and what is the result? Why does that happen?
Water. Osmotic gradient. Water doesn't like to be made hypotonic, it would much rather osmose with it's solutes.
Is Cl absorbed or secreted?
Cl is pumped through basal membrane and loves escaping out through the apical membrane. This happens because the lumen is "more positive" than the cell.
Describe the distinction between the major bronchi and the alveolar ducts.
In large bronchi and airways, epithelia secrete Cl more. In the alveoli, they absorb Na.
What does blood pressure do in the alveoli and how do epithelia fix the problem?
Blood pressure is so high in small alveoli that fluid is kicked out of the cell into the lungs! Na absorption takes water back in with it. BUT THIS REQUIRES ENERGY FROM MITOCHONDRIA.
But why is there a "wet" layer in the alveoli anyway?
Facilitate gas exchange.
How do the pseudostratified epithelia in the trachea move stuff?
Cilia. With help from mucus and the Cl secretion. When there's too much mucus, the epi secrete more Cl and increases fluidity. Vice-versa.
What is the primary defect in cystic fibrosis, from a physio standpoint?
The defective CFTR gene does not produce the apical Cl channel.
Describe the pathology of a missing Cl channel in respiration.
1. Not enough fluid is secreted for ciliary movement.
2. Mucus containing bacteria remain resident.
3. Infection rates rise and cannot be resolved.
Describe the pathology of a missing Cl channel in digestion.
1. The pancreas cannot secrete digestive enzymes.
2. The buildup of pancreatic precursors can lead to auto-activation of digestion: pancreatitis.
Describe the pathology of the missing Cl channel in sweat.
1. The gland is still capable of secreting Cl via another gene, so the NaCl enters the duct as normal.
2. However, the duct is missing the Cl channel, so Cl cannot be secreted and conversely, very little Na is induced to leave the lumen.
3. The NaCl concentration of sweat is very high compared to functional ducts.