Terms in this set (94)
enteric nervous system
-on wall of entire GI tract
-independent of brain
-controls contractions of circular and longitudinal muscles
-Ach=stim, increases tone/mvmt
Extrinsic nervous system: parasympathetic
*increase GI function
extrinsic nervous system: sympathetic
*inhibit GI function
-hyperactivity of VIP/Ach
-inhib of VIP/Ach
-contractile ring & relaxation
-esophag & intestines
2 types of "mixing"
-uses smaller regions of contraction
-uses larger regions of contraction
1. swallowing: voluntary phase
-food goes to back of mouth where there's touch receptors that begin the swallowing reflex
2. swallowing: pharyngeal phase
-swallowing reflex initiated by food in back of mouth
-moves epiglottis & vocal cords over airways, soft palette covers nasal airways
-upper esophag. sphincter relaxes
-peristaltic contractions in upper esophag drive food down
3. swallowing: esophageal phase
-primary peristalsis (initial wave of contraction)
-secondary peristalsis (another wave of contraction if food still in esophag)
-stomach acid leaks up past LES
-poor LES tone
-can get barrets esophag/cancer
what causes LES to relax and let food pass into stomach?
if LES is NOT relaxed..
-b/c lack VIP
-triggered by swallowing
-vago-vagal reflex is active
-strong peristaltic waves
-large contraction @ pylorus...pylorus contracts and pushes all the food back (retropulsion)
-only liquified food can pass through a closed pylorus
-occur during fasting
-once every 90mn
*motillin hormone starts this
-contractions from stomach to colon
-released due to meat/distension in stomach
-increases waves of contraction/motility of stomach
once food enters the duodenum...
-decreases emptying from stomach
-CCK, secretin, GIP released from SI turn the stomach emptying off
-food in intestines
-turns off motility stomach
acid in duodenum stimulates....
secretin release (decreases gastric emptying)
fats in duodenum stimulates...
CCK/GIP release (decreases gastric emptying)
-food stretches intestine causing contractions BEHIND food, relaxation downstream
-stretch in stomach, increases peristalsis in the ileum, forcing chyme into cecum
-contract large region all at once
-push everything out at once
-caused by an irritant
-prevents backflow into SI
-food/pressure in colon inhibits mvmt of food from ileum into colon
-sphincter b/w ileum & colon is closed
-if appendix is inflamed it can close this valve
parotid salivary gland
-most of stimulated saliva
saliva is always...
ductal cells (in the salivary duct cell)
-CA catalyzes the reaction
-K & bicarb into lumen (saliva)
-Cl into blood
-K & bicarb
-mucin, amylase, R-factor, lysosyme
-Ach=stim acinar cells & mucus
-VIP=stim watery output, vasodil
-NE=increase mucus/enzymatic output, decrease watery output, vasocon
-body of stomach
-secretes intrinsic factor & HCl
2 types of glands in the stomach
-parietal, chief cells
in a parietal cell..
*H/K exchanger (pulling H into lumen)
-bicarb into blood
-alkaline flow into blood (fixed later by pancreas)
all these cells increase the action of the parietal cell, and increase the H+ secreted
what inhibits the parietal cell from secreting H+?
-somatostatin (from D cells)
zymogens and bicarb (to neutralize acid)
-enterokinase converts it to trypsin
-this activates other zymogens
breaks down carbs
pancreatic lipase, phospholipase, cholesterol esterase....
breaks down fats
lack CFTR channel (cystic fibrosis)
-no bicarb leaving the cell; can't neutralize stomach acid
-no bicarb to breakdown mucus in ducts (resp prob)
pancreatic high flow rate =
lots of bicarb, low Cl-
in response to fats/proteins...
CCK acts on acinar cells to release zymogens
in response to acid from the stomach into the small intestine...
-S cells release secretin
-secretin increases cAMP in the ductal cells, and release bicarb rich secretions
primary stim. of acinar cells is...
(Ach also stimulates zymogen release)
primary stim. of ductal cells
cholesterol makes bile salts in..
-conjugated into taurine/glycine (more soluble)
sphincter of oddi: not eating
-closed if NOT eating, so bile moves to gall bladder, where its concentrated by removing H2O/ions
once you start eating...
-CCK/secretin are released in intestines
-CCK relaxes the sphincter of oddi so it opens
-causes gallbladder to contract, and push bile into SI
once bile's in the duod...
-we can digest fats
-once bile salts are in the ileum, they're recycled back to the liver (portal circ)
what stimulates bile synthesis
nothing! its always being made
pancreatic enzymes in the intestinal lumen breakdown proteins into...
brush border enzymes break oligopeptides down into...
-amino acids (absorbed through aa specific proteins)
-di/tripeptides (absorbed through peptide transporter; broken down into aa in cell)
TG + bile salt
micelle diffuse into the epi cell of the small intestine...
where its formed into a chylomicron
chylomicron is then exocytosed into the...
-phospho. shell w/proteins
-exocytosed into lymph
-moves into lacteels, then the liver
interstitial cells of cajal
-regulate slow wave activity
-pacemakers of GI
-gap junctions b/w this and smooth muscle
saliva low flow rates
saliva high flow rates (during a meal)
(less time to modify saliva and remove Na)
chief cells secrete...
-pepsinogen=pepsin (needs HCl to become active)
chief cells secretion (pepsinogen) is stimulated by..
G cells stimulate...
-parietal cells (increase H secretion)
ECL cells are stimulated BY...
D cells are stimulated BY...
-secretin, glucagon, CIP, VIP
-secretes somatostatin which INHIBITS G-cells (gastrin) and inhibits parietal cells (HCl)
peptic ulcer disease
-ulcers in stomach
*imbalance b/w mucus production & acid secretion
causes of peptic ulcer disease
-zollinger-ellison syndrome (tumor produces gastrin, which stimulates ECL/parietal cells=overprod of acid)
other pancreatic enzymes
CFTR channel in pancreatic ductal cell
-allows Cl- to LEAVE the pancreatic ductal cell
-this way, Cl can come back in, and bicarb can go out via/ the Cl/bicarb exchanger
large intestinal crypts
-mucus secreting crypts (no villi)
-stimulated by tactile response, parasymp
-protects lining from irritation/adherence for feces
-irritations increase H2O secretion
-mass mvmts to remove irritant
-bacteria toxins increase NaCl- secretion (CFTR channel)
-increase Na secretion, so H2O will follow
*losing H2O b/c of increased secretion in crypt cells
where are carbs digested?
-saliva (parotid glands)
-brush border enzymes finish digestion
-simple sugars (glucose, galactose, fructose) absorbed
if we lack lactase=osmotic diarrhea
-lots of lactose in lumen, which holds water to it
-can't breakdown lactose into glucose and galactose
where are proteins digested?
-small intestine (pancreatic enzymes, brush border enzymes)
how are fats digested?
-emulsify fats in small intestine w/bile salts
-now have TG w/bile salts on it=micelle
-now the micelle can diffuse into the enterocyte
Vit B12 absorption
-needed for RBC production
-prob w/parietal cell (ulcers)=can't absorb B12