GIT 3: SECRETORY FUNCTIONS Flashcards
intrinsic nervous system in response to: tactile stimulation, chemical irritation and distention
enteric nervous system
intrinsic nervous system
Meissner’s plexus
parasympathetic nerves
increases rate of glandular secretion
salivary glands, esophageal gastric glands, brunner’s glands in duodenum, pancreas
glossopharyngeal and vagal nerves
increases rate of glandular secretion
parasympathetic
pelvic nerves
distal colon
sympathetic
alone: slight increase in secretion
superimposed with parasympathetic or hormonal stimulation
vasoconstriction decrease secretion
sympathetic
primary control is by parasympathetic
controls submandib and sublingual glands
facial nerve
serous secretion (saliva)
ptyalin (alpha amylase) digests starches
mucus secretions (saliva)
mucin lubrication
acinar cells
pytalin mucin
cl channels
isotonic with plasma, slight alkaline
primary secretion of salivary
duct cells reabsorb Na, Cl and secrete K, and HCO3
hypotonic, alkaline
secondary secretion
saliva is hypotonic and slightly alkaline
at rest salivary secretion
isotonic and alkaline
stimulated salivary secretion
types of tubular glands
gastric/oxyntic glands
pyloric glands
oxyntic glands cells / gastric gland cells
mucous neck cells: mucus
parietal cells: HCL, intrinsic factor
peptic cells: pepsinogen
pyloric glands cells
g cells: gastrin
mucous cells: mucus
located at the parietal cell
essential for absorption of Vitamin B12 in ileum
secreted along with HCL
intrinsic factor
located within the parietal cells
secreted by gastric cells just before ingestion of a meal
increases appetite and food intake
ghrelin
secreted in response to acid, fat, protein breakdown products and hyper or hypo osmotic fluids or irritating factors in upper small intestine
inhibits gastric activity
enterogastrones
inhibitory enterogastrones
acid
secretin
CCK
somatostatin
Prostaglandin E2
GIP
VIP
GLP-1
Calcitonin
Peptide YY
release stimulated by
distention of the stomach
presence of small peptides and amino acids
stimulation of the vagus n.
gastrin
enterogastrone
secreted throughout the GI tract in response to H+ in the lumen
inhibited by the vagus
inhibits the release of all GI hormones
Inhibits gastric H+ secretion
sight, smell, thought, taste of food
cerebral cortex, appetite center of amygdala and hypothalamus - DMN of vagus nerve
30% of acid secretion
cephalic phase
distenstion stomach/ products or protein digestion/ vagal aff/ brainstem/ vagal eff
long vagovagal reflex
local enteric reflex
gastrin-histamine mechanism
60 percent of acid secretion
gastric phase
food in duodenum
gastrin, nervous mechanism
10 percent of gastric acid secretion
intestinal phase
gastrin effects of secretion of G cells
increase gastric secretion
increase gastric motor activity
increase gastric blood flow
trophic action on the gastric mucosa
gastrin
increase water and electrolyte secretion of liver pancreas and small interstine
increase pancreatic enzyme secretion
stimulates lower esophageal sphincter and gallbladder contraction
extra-gastric effects of gastrin
an ulcerative lesion of the gastric/duodenal mucosa
caused by the erosive and digestive action of H+ and pepsin on the mucosa
loss of protective mucous barrier
excessive H+ and pepsin secretion
combination of two
peptic ulcer disease
mucus glands of duodenum
mucus for protection from digestion with large amount of bicarbonate to neutralize acid
secretes alkaline mucus in response to tactile/irritating stimuli in duodenum, vagal stimulation, GI hormones
inhibited by sympathetic stimulation
brunner’s glands
secretes mucus in intestinal villi
goblet cells
secretes large quantities of water and electrolytes
reabsorbs water and electrolytes with end products of digestion
contain digestive enzymes
enterocytes
regulates enteric secretions
local enteric nervous system
regulates colonic secretion
direct tactile stimulation of epithelial cells
local nervous reflex
parasympathetic innervation
pancreatic secretions
small volume of initial pancreatic secretion
stimulated by CCK
acinar cells
modify initial secretions by secreting bicarbonate and absorbing chloride
permeable to water
stimulated by secretin
ductal cells
same Na and K concentration than plasma
high volume
higher bicarbonate concentration than plasma
much lower chloride concentration than plasma
pancreatic amylase, lipase and proteases
pancreatic secretions
secreted by I cells
stimulates chief cells, pyloric sphincter, gallbladder contraction, enteropeptidase, enteric and colonic motor activity, trophic action on pancreas
cholecystokinin
secreted by S cells in duodenum
acts on pancreatic ductal cells to increase bicarbonate secretion
stimulates pancreatic secretion of watery alkaline juice
stimulates brunner’s glands, chief cells
stimulates water and bicarbonate secretion by liver, increases rate of bile flow
inhibits parietal cell, gastric and enteric motor activity
secretin
stimulates digestive enzyme secretion by the acinar cells
potentiates secretin effects
acetylcholine
pancreatic secretion
pancreatic enzyme secretion (acini)
cck
pancreatic secretion
pancreatic bicarbonate rich fluid
secretin
releases enzymes into acini
pancreatic secretion
vagal stimulation
stimulated by CCK
modification of primary secretion is primarily stimulated by secretin
contains bile salts, cholesterol, and phospholipid, bile pigments stored and concentrated in the gall bladder
bile
micellar solution: 10:3:1
BA, phophatidylcholine:cholesterol
