Flashcards in GI Secretion and Digestion Deck (23):
The _____________ uses more energy than any other process in the body.
secretion of acid
What are the functions of stomach acid?
- Denatures protein, which prepares them for digestion
- Kills bacteria
How does the stomach protect itself from acid?
Tight junctions between epithelial cells
High turnover of epithelial cells
____________ increase mucus production.
The ______________ have branches.
Prior to binding intrinsic factor, cobalamin binds to _____________.
salivary R protein, which then gets cleaved by gastric proteases
Intrinsic factor, coupled to cobalamin, gets taken up by _________________.
receptors in the terminal ileum
What three molecules stimulate gastric secretion?
What is the alkaline tide?
When you eat a big meal, the gastric parietal cells secrete more protons, which pumps more bicarb into the blood.
True or false: sodium passes through a pore in the intestines.
False. Chloride passes through CFTR, but sodium passes between cells.
The surface area of the villi is _______ that of the crypts.
The main difference between carbohydrate digestion and protein digestion is that ______________.
carbohydrates have to be broken down to monomeric subunits, while proteins do not
Sodium binding to the SGLT1 receptor induces ____________.
absorption into the cell
Explain how the apical H+/K+-ATPase drives the secretion of Cl- and H2O into the stomach.
The creation of protons inside the cell also creates bicarb, because the reaction is catalyzed by carbonic anhydrase. The excess intracellular bicarb exits the cell via the basolateral Cl-/HCO3- exchanger. Chloride then builds up inside the cell and is transported out of the apical membrane down its concentration gradient. Water follows this chloride.
Gastrin and acetylcholine work by _______________, while histamine works by ______________.
raising intracellular calcium; raising cAMP, which starts a cascade that ultimately phosphorylates the H+/K+-ATPase
What are ECL cells?
Enterochromaffin-like, they secrete histamine and gastrin in response to PNS stimulation (via Ach) or local gastrin
True or false: the stomach is always secreting acid.
False. Between meals the pH of the stomach can be as high as 7.
The gastric phase and intestinal phase are mediated by ____________ effects.
local (distension and partially digested proteins in the stomach and partially digested amino acids in the small intestine)
Oxyntic cells are _____________.
Basal acid secretion is highest in the _____________.
What are canaliculi?
Little pillars of tissue that give parietal cells more surface area to secrete acid through
Which sugar does not need sodium as a co-transporter to be absorbed by the small intestine?
Fructose (absorbed by the GLUT 5 receptor)