Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
28 Cards in this Set
- Front
- Back
What is the average daily volume of ingested or secreted fluids, and from what sources?
|
9L:
2-diet, 1-saliva, 2-gastric juice, 3-pancreatic juice and bile, 1-small intestine |
|
How much fluid is absorbed versus excreted on average daily?
|
small intestine r/a's ~7L, colon r/a's ~2L
100-200mL e/c in feces |
|
What is there net absorption of in the jejunum?
|
NaHCO3 (also monosaccharides, AAs)
|
|
Transport in jejunal epithelial cells parallels that of which part of the kidney?
|
early proximal tubule
|
|
What are the 4 main ways Na is reabsorbed in the small and large intestines?
|
1. nutrient-stimulated: Na-monosacc and Na-AA cotransport (w/facilitated diffusion into blood)
2. high pH stimulated: apical Na-H exchange (duod and jej) 3. interdigestive: parallel Na-H and HCO3-Cl exchangers (ileum and prox colon) 4. diffusion via apical ENaC channels (distal colon) |
|
What is there net absorption of in the ileum?
|
NaCl (and sugar and AAs)
|
|
Transport in epithelial cells of the colon parallels that of which part of the kidney?
|
principal cells of the late distal tubule and collecting ducts
|
|
What effect does aldosterone have on Na transport in the colon?
|
induces synthesis of ENaC channels, to increase Na r/a and K s/c (like in principal cells of LDT and CDs)
|
|
What are the 3 main ways Cl is reabsorbed in the small and large intestines?
|
1. voltage-dependent: passive r/a (follows Na), cellular or paracellular
2. electroneutral: Cl-HCO3 exchanger in ileum and colon 3. interdigestive: parallel Na-H, HCO3-Cl channels in ileum and prox colon |
|
What is the mechanism of K reabsorption and/or secretion in the small intestine?
|
K r/a passively via solvent drag (no s/c)
|
|
What is the mechanism of K reabsorption and/or secretion in the large intestine?
|
1. passive paracellular (net) s/c of K
2. active K s/c via Na-K-2Cl pump (stimulated by aldosterone) |
|
Does diarrhea cause hypo- or hyperkalemia?
|
hypokalemia; flow rate-dependent secretion of K (like in distal tubules), causes excessive K s/c, e/c
|
|
What is the mechanism of Cl secretion in the intestinal crypts?
|
in response to secretagogues (i.e. ACh, VIP); NaK2Cl pump, and diffusion through apical Cl channels (CFTR)
|
|
What substances are secreted by the crypts, in addition to Cl?
|
Na and water passively follow Cl s/c
|
|
What type of diarrhea results from cholera toxin?
|
secretory diarrhea (excessive secretion overwhelms absorptive capacities of intestine/colon)
|
|
What is the mechanism by which cholera toxin causes diarrhea?
|
cholera toxin binds to apical receptors of crypt cells, activates AC, cAMP, permanently opening apical Cl channels; Na and water follow
|
|
What are the fat soluble vitamins?
|
A, D, E, K
|
|
How are fat soluble vitamins absorbed?
|
incorporated into micelles, diffuse across apical membrane, incorporated into chylomicrons and extruded into lymph
|
|
What are the water soluble vitamins?
|
B1, B2, B6, B12, C, biotin, folic acid, nicotinic acid, pantothenic acid
|
|
How are most water soluble vitamins absorbed? What is the exception?
|
via Na-dependent cotransport mechanisms; except B12
|
|
What is the mechanism of B12 absorption?
|
B12 is transferred to intrinsic factor in duodenum (resistant to degradation by panc proteases), binds to receptor in ileum and is absorbed
|
|
What is a critical consequence of a gastectomy? How is this remedied?
|
loss of gastric parietal cells = no intrinsic factor = pernicious anemia; give B12 injections (to bypass need for GI r/a)
|
|
What does Ca depend on for intestinal absorption?
|
active vitamin D (1,25-dihydroxycholecalciferol) (activated in kidney)
|
|
How does 1,25-dihydroxycholecalciferol promote Ca r/a?
|
it induces synthesis of vitamin D-dependent Ca-binding protein (calbindin D-28K) in intestinal epithelial cells
|
|
What happens in vitamin D deficiency or chronic renal failure?
|
inadequate Ca absorption = osteomalacia (adults) or rickets (kids)
|
|
In what forms is iron absorbed across the apical membrane of intestinal epithelial cells?
|
as free iron or heme iron (heme iron is then converted to free iron in cell)
|
|
How is iron transported across the basolat membrane of intestinal epithelial cells?
|
free iron binds to apoferritin and is transported across memb
|
|
What is the form in which free iron circulates in the blood, and where does it go to?
|
bound to transferrin, goes to storage sites in liver, then to bone marrow for synthesis of hemoglobin
|