PHY 503: B12/WATER/ELECTROLYTE ABSORPTION AND
STOOL: TEST QUESTIONS WITH CORRECT ANSWERS
What are intestinal villi and crypts responsible for? -- Answer ✔✔ absorbing
nutrients/electrolytes and secreting electrolytes into the intestinal lumen, respectively
What do Paneth cells do? -- Answer ✔✔ sense bacteria in the small intestine through a
MyD88-dependent TLR activation, triggering an antimicrobial immune response that
limits the ability of the bacteria to penetrate the mucosal surface and enter the body
Where in the GI tract does most fluid absorption occur? -- Answer ✔✔ the small
intestine
Where does the fluid entering the intestines come from? -- Answer ✔✔ 25% from diet,
the rest is secreted into the GI tract from endogenous sources (salivary, gastric,
pancreatic, biliary glands)
What does the small intestine have net absorption and secretion of? -- Answer ✔✔ net
absorption of sodium, potassium, chloride, and water; net secretion of bicarbonate
What does the large intestine have a net absorption and secretion of? -- Answer ✔✔
net absorption of sodium, chloride, and water; net secretion of potassium and
bicarbonate
, What is the typical tonicity of chyme that leaves the duodenum and what would happen
if the tonicity was different? -- Answer ✔✔ isotonic to the interstitial fluid; if it were
hypotonic to the interstitial fluid the intestine would absorb water, and if it were
hypertonic water would be secreted into the lumen
What are the four mechanisms of sodium absorption in the intestines? -- Answer ✔✔ 1)
electrogenic diffusion into the cell through aqueous channels
2) coupled with nutrient uptake (glucose, galactose, amino acids)
3) electroneutral uptake of sodium and chloride through a Na+/H+ exchanger and Cl-
/HCO3- exchanger
4) coupled with extrusion of H+ in the absence of any parallel Cl- movement in the
duodenum and jejunum only (occurs when GI luminal pH is alkaline)
How can chloride be absorbed in the intestines? -- Answer ✔✔ can follow Na+
paracellularly along with water, or can move transcellularly through Cl- channels due to
negative electrical potential in the gut lumen as a result of the Na+ uptake
What is the mechanism of extrusion of Na+ across the enterocyte basolateral
membrane? -- Answer ✔✔ the Na+/K+ pump
What is the major mechanism for postprandial Na+ absorption and how does it occur? -
- Answer ✔✔ sodium-nutrient coupled transport in the jejunum; involves electrogenic
net movement of Na+ from apical to basolateral side, resulting in a change in
transepithelial voltage due to the loss of cations from the lumen
STOOL: TEST QUESTIONS WITH CORRECT ANSWERS
What are intestinal villi and crypts responsible for? -- Answer ✔✔ absorbing
nutrients/electrolytes and secreting electrolytes into the intestinal lumen, respectively
What do Paneth cells do? -- Answer ✔✔ sense bacteria in the small intestine through a
MyD88-dependent TLR activation, triggering an antimicrobial immune response that
limits the ability of the bacteria to penetrate the mucosal surface and enter the body
Where in the GI tract does most fluid absorption occur? -- Answer ✔✔ the small
intestine
Where does the fluid entering the intestines come from? -- Answer ✔✔ 25% from diet,
the rest is secreted into the GI tract from endogenous sources (salivary, gastric,
pancreatic, biliary glands)
What does the small intestine have net absorption and secretion of? -- Answer ✔✔ net
absorption of sodium, potassium, chloride, and water; net secretion of bicarbonate
What does the large intestine have a net absorption and secretion of? -- Answer ✔✔
net absorption of sodium, chloride, and water; net secretion of potassium and
bicarbonate
, What is the typical tonicity of chyme that leaves the duodenum and what would happen
if the tonicity was different? -- Answer ✔✔ isotonic to the interstitial fluid; if it were
hypotonic to the interstitial fluid the intestine would absorb water, and if it were
hypertonic water would be secreted into the lumen
What are the four mechanisms of sodium absorption in the intestines? -- Answer ✔✔ 1)
electrogenic diffusion into the cell through aqueous channels
2) coupled with nutrient uptake (glucose, galactose, amino acids)
3) electroneutral uptake of sodium and chloride through a Na+/H+ exchanger and Cl-
/HCO3- exchanger
4) coupled with extrusion of H+ in the absence of any parallel Cl- movement in the
duodenum and jejunum only (occurs when GI luminal pH is alkaline)
How can chloride be absorbed in the intestines? -- Answer ✔✔ can follow Na+
paracellularly along with water, or can move transcellularly through Cl- channels due to
negative electrical potential in the gut lumen as a result of the Na+ uptake
What is the mechanism of extrusion of Na+ across the enterocyte basolateral
membrane? -- Answer ✔✔ the Na+/K+ pump
What is the major mechanism for postprandial Na+ absorption and how does it occur? -
- Answer ✔✔ sodium-nutrient coupled transport in the jejunum; involves electrogenic
net movement of Na+ from apical to basolateral side, resulting in a change in
transepithelial voltage due to the loss of cations from the lumen
