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45 Cards in this Set

  • Front
  • Back
Average volume of secreted and ingested fluid entering body daily?
8.5 liters

(largest contributor - stomach)
Average volume of secreted and ingested fluid that is absorbed by body daily?
8.3 liters

(only 200 ml not absorbed!)
Name the two types of secretions and what their functions are.
1) serous - water and electrolytes to provide proper environ for digestion
2) protein - enzymes and mucus to digest and lubricate/buffer respectively
List the types of glands involved in secretion.
1) Mucous - single cell (goblet)
2) Tubular - invaginations of epithelium that contain secretory cells (gastric pits, intestinal crypts)
3) Compound - outside of gut wall, acini and ducts, primary secretion into center of acinus (ex. salivary, pancreatic)
Describe the difference between primary and seconday secretion that occurs in compound glands.
Primary - secretion into center of acinus
Secondary - cells lining ducts modify the secretion by adding electrolyte and water components directly into the duct as it proceeds toward the lumen of the gut
List the two mechanisms of intracellular mediators of secretion:
1) G protein - AC - cAMP - secretion (B adrenergic agents, VIP, secretin family, cholera toxin)
2) PIP2 splits - IP3 - intracellular Ca2+ release - secretion (ACh, CCK, TKs)
Name three glands that provide salivary secretion and the type of secretion.
1) parotid - serous only
2) submaxillary - serous and mucous
3) sublingual - serous and mucus, but mostly mucous
Name the functions of saliva:
1) mucous - lubricates and keeps pH normal
2) enzyme - ptyalin (alpha amylase) digests CHO and lingual lipase digests lipids
3) taste, speech, preventing oral infections
What makes up the secretion produced in primary secretion of a salivary gland?
water, electrolytes (Na, K, Cl, HCO3) mucus, enzyme

* electrolytes secreted are isotonic
What makes up the secretion produced in secondary secretion of a salivary gland?
modification of primary secretion, extract Na and Cl from the soltn and add K and HCO3 (more electrolyte is removed than added)

*solution is now hypotonic
How does flow rate affect salivary secretion?
Fast flow rate - not much time for secondary secretion - secretion most resembes primary secretion
Slow flow rate - more time for secondary secretion and exchange
What is the tonicity of a salivary secretion that had a SLOW flow rate?
Hypotonic (low in NaCl and HCO3
What is the tonicity of a salivary secretion that had a FAST flow rate?
What happens to electrolyte levels as the salivary secretion flow rate increases to above ~2 ml/min?
they level off (except Cl- still increasing)
Is control of salivary secretion hormonal, neural, or both?
neural only -- there is NO hormonal control
Are sympathetic NS and parasympathetic NS excitatory or inhibitory in salivary glands?
both are excitatory and stimulate secretion
Name the NTs in neural control of salivary secretion, and tell about their mechanisms.
Para - releases ACh, and VIP - stimulate acinars directly - since BVs dilated by VIP, secretion high in ptyalin and serous component ** most potent secretion stimulator
Symp - NE activates alpha and beta receptors - serous component decreased - high mucous concentrations
What is the optimal pH for ptyalin (salivary amylase) and where does it exist?
pH 7 (range pH 4-11) - begins in mouth, and if attached to bolus or inside bolus, can keep alkaline pH through stomach, intestine, and rest of GI tract and continue to digest CHO
What is the optimal pH for lingual lipase?
pH 4 (range pH 2-8) - continues to digest thru stomach
Name the 5 types of gastric secretion.
1) H+ (parietal/oxyntic cells)
2) Pepsinogen (chief cells)
3) Lipase (chief cells)
4) Intrinsic factor (parietal/oxyntic cells)
5) Mucus (mucous cells)
What do parietal (oxyntic) cells secrete?
1) H+
2) Intrinsic factor
What is H+ responsible for in the stomach?
1) convert pepsinogen to pepsin, which digests proteins at low pH
2) maintain low pH for continued pepsin action and to prevent bacterial growth
Where are parietal cells located in the stomach?
in the oxyntic glands located in the fundus and corpus of the stomach
What do chief cells secrete?
1) Pepsinogen
2) Gastric lipase
Where are cheif cells located?
oxyntic gland of stomach
What two kinds of lipases in the body liberate a single free fatty acid and a diglyceride from a TG and have acidic pH optimums?
lingual lipase (3rd FA) and gastric lipase

* pancreatic lipase is different
For what purpose is intrinsic factor needed?
to absorb vitamin B12 in the ileum
Where is mucus secreted from in the stomach and what is its main purpose here?
- secreted from mucous cells in surface epithelium and in neck of oxyntic gland
- protects stomach from autodigestion
What kind of glands are oxyntic glands and what kind of cells are located within these glands?
- tubular glands (from gastric pits) in fundus and corpus areas
- parietal cells, chief cells, mucous neck cells
What cells are more numerous at the base of oxyntic glands?
parietal cells
What is the purpose of cannilculi formation in parietal cells upon their stimulation?
canniliculi increase surface area of parietal cells for more H+/K+ ATPase (proton pumps) thus more H+ secretion (and K+ import)- final gastric pH <1
What generates H+ inside of the parietal cell?

(HCO3- formed from rxn diffuses into blood when exchanged with Cl-)
What is omeprazole and how does it work?
a proton pump (H+/K+ ATPase) inhibitor - decreases amount of H+ secreted - increases pH in lumen -- used to treat gastric ulcer disease and gastroesophageal reflex (GERD)
What is the net reaction in the parietal cell?
H2O + CO2 + NaCl --> NaHCO3 (blood) + HCl (lumen)
What is secreted from the basolateral membrane of the parietal cell during high rates of stimulation vs. low rates of stimulation?
high stimulation - HCl secreted (via HCO3/Cl- exchanger)
low stimulation - NaCl secreted (Na+/K+ ATPase)
** hthe reason for this is that when there is low stimulation, less H+ out/K+ in, lower conc. of K+ in cell, want more K+ inside cell Na+/K+ going strong, Na+ out, combine with Cl- for NaCL
Name the 3 controls of acid secretion in parietal cells.
1) neural (enteric and parasympathetic)
2) hormonal (gastrin)
3) paracrine (histamine, SS)
How does parasympathetic stimuation (vagal activation) increase acid secretion?
1) ACh
2) Histamine release via enterochromaffin-like cells
3) Gastrin secretion by antral G cell (using GRP)
To what are type of receptors does gastrin bind, and what do the do when stimulatated?
- when stimulated intracellular Ca2+ is elevated and HCl secretion occurs
- competitive antagonism also exists
What type of receptors in the stomach are activated by histamine and what happens when they are activated?
- H2 receptors on parietal cells
- increases cAMP and HCl secretion
What does cimetidine do?
- blocks H2 receptors to treat gastric ulcer disease (by decreasing HCl secreted)
What kinds of receptors does SS bind to and what happens when they are stimulated?
- SS receptors
- decreases cAMP and HCl secretion and inhibit gastric secretion
Name and describe the phases of acid secretion.
1) Cephalic
(think about eating a meal)
2) Gastric
(presence of meal in stomach)
3) Intestinal
(presence of chyme in intestine)
What happens in the cephalic phase of acid secretion?
- vagal reflex stimulates parietal cell directly and induces the release of gastrin from the G-cell
What happens in the gastric phase of acid secretion?
- maximal stimulation of acid secretion via neural stimulation of parietal cell
- G cell stimulation by distention, vagal, and aas
What happens in the intestinal phase of acid secretion?
- inhibit acid secretion via fall of pH inhibiting gastrin
- neural reflexes due to presence of food in duodenum inhibits acid secretion (GIP, CCK, secretin, enterogastrone)