GI tract secretion Flashcards
Digestive enzymes are secreted towards the
lumen
hormones for regulation are secreted towards the
blood
GI-associated glands
salivary
pancreas
liver
4 Type of accessory GI assoc. glands
single-mucous glands
tubular glands
esophageal glands
brunner’s glands
Gastric glands and intestinal glands are an example of what type of glands
tubular galnds (stomach - colon)
esophageal glands are also known as
submucosal glands
the most potent stimulus for secretion
food in the GI tract
other types of stimulation for secretion
mechanical
distention of gut wall
chemical irritation
hormones
gastrin
GIP
GLP-1
are hormones that stimulate
GI secretion
Mucus fxns.
protects gut mucosa from damage by lowering resistance to slippage
resistant to digestive enzymes
restrains enteric microbiota
buffer for small amounts of acids
salivary glands of the head
parotid
mandibular
sublingual
The salivary glands of the head can be categorized as
serous or mucus
parotid salivary gland is
serous
mandibular salivary gland is
serous + mucous
sublingual gland is
serous + mucous
name two salivary digestive enzymes
salivary amylase
salivary lipase
fxn. of salivary amylase
breakdown of starch into maltose
not present in cattle, dog, cats or horses
fxn. of salivary lipase
breakdown of lipids, limited action in farm animals
General fxns. of saliva
lubrication of food
slightly basic in dogs and ruminants
inhibits bacterial growth
prevents tooth decay
t/f in dogs, saliva works as an evaporative cooling
true
t/f in cows the fluid environment is to neutralize acid
true
type of epithelium in the mucosa, submucosa and muscularis layers
thick stratified squamous epithelium
located in the submucosal layer of the esophageal wall
consists of mucous cells with or without a minor serous component and produces mucins and bicarbonate
prevents mucosal excoriations (peeling), stomach acid caused ulceration
esophageal gland
t/f the stomach contains gastric rugae
true
known as foveolar epithelium, similar to the goblet cells secreting mucus, covering the surface and gastric pit
surface mucous cells
location of gastrics glands in stomach
caridac
fundic = oxyntic
pyloric
4 types of secretory cells in gastric glands
neck cells
chief cells
parietal cells
enteroendocrine cells
mucus, continuation of the surface mucous cells
neck cells
secrete pepsinogen
chief cells
secrete HCL and intrinsic factor
parietal oxyntic cells
3 types of enteroendocrine cells
ECL celld
D cells
G cells
ECL enteroendocrine cells secrete
HIstamine
D enteroendocrine cells secrete
somatostatin
G enteroendocrine cells secrete
gastrin
gastric epithelial cells and gland cells secrete
intrinsic factor B12
mucus
water
pepsinogen
HCl
specific site of parietal cells that secretes HCl
apical membrane containing canaliculi
t/f ATPase proton pump is in charge of HCL transport
trye
1 characteristic of parietal cells
contain the proton pump
mechanism to increase acid production
increasing the surface area in the apical membrane with extensive caniculi by fusing tubular and vesicular organelles containing high concentration of H-K pumps when stimulated by histamine, gastrin and ACh
What neurotransmitter is involved in neural/endocrine regulation of acid secretion?
ACh
3 steps of the neural/endocrine mechanism of acid secretion
amino acids in the stomach stimulate and ACh from vagus nerve stimulate gastrin sceretion
gastrin stimulates histmine release form ECL cells
Histamine stimulates parietal cells to secrete HCl
in the neural/endocrine secretion mechanism, whicih substance is the more important regulator?
histamine
gastrin
ACh
histamine
Which receptor of parietal cells does histamine act on?
H2 in a paracrine manner
Which receptor of parietal cells does ACh act on?
M receptors
What substance inhibits ACh, and which cells produce it?
somatostatin produced by D cells
3 mechanism of gastric acid secretion regulation
aluminum or magnesium hydroxide
H2 blockers
proton pump inhibitor
3 phases of gastric secretion
cephalic phase
gastric phase
intestinal phase
The cephalic phase of gastric secretion is mediated by___ and will cause _____
vagus nerve
PSNS excitement and pepsin and acid production
In what phase of gastric secretion is this occurring?
local nervous secretory reflexes
vagal reflexes
gastrin-histamine stimulation
gastric phase
In what phase of gastric secretion is this occurring?
nervous mechanisms
, and hormonal mechanisms
intestinal phase
what inhibits gastric secretion in intestinal phase?
Reverse enterogastric reflex via myenteric nervous system
hormones
The reverse enterogastric reflex via the myenteric nervous system is initiated by
presence of food in upper intestine
Hormones that inhibit gastric secretion
GIP
GLP-1
somatostatin
Where does most of the enzymatic digestion occur?
small intestine
What is secreted and reabsorbed in the small intestine during the digestive process?
water
Water flows in the small intetsine in response to
osmotic gradients
2 mechanisms of secretion that etsablish osmotic gradient pulling water into lumen of intestine
Increases in luminal osmotic pressure resulting from influx and digestion of foodstuffs
Crypt cells actively secrete electrolytes, leading to water secretion
cyclic AMP-dependent chloride channel - cystic fibrosis transmembrane conductance regulator CFTR
Water secretion mechanism by crypt cells in small intestine
Mutation in cyclic AMP-dependent chloride channel causes
cystic fibrosis
steps of water secretion mediated by cyclic cAMP
Cl ions enter the crypt cells by contrasnport with Na and K
activation of adebyl cyclase leads to generation of cAMP
Elevated intracellular concentrations of cAMP in crypt cells activate the CFTR, resulting in secretion of chloride ions into the lumen.
Accumulation of negatively-charged chloride anions in the crypt creates an electric potential that attracts sodium, pulling it into the lumen, across tight junctions - the net result is secretion of NaCl.
Secretion of NaCl into the crypt creates an osmotic gradient across the tight junction and water is drawn into the lumen
example of sickness cause by the excessive activation of cAMP
cholera
Abnormal activation of the cAMP-dependent chloride channel (CFTR in crypt cells causes
massive secretion of water due to the chloride channels stuck in open position, resulting in massive secretion of water
2 effects that hormone secretion in the small intestine cause
ihibit gastric secretion
stimulate insulin sercetion
incretins:
GIP
GLP-1
induce insulin secretion
inuslin is serceted from where in the pancreas?
islets
fxns. or large intestine
mucous secretion
reabsoroption of water and electrolytes
Crypts of Lieberkuhn
Large intestine glands with a lot of goblet cells for mucus production
t/f Chemical digestion is completed in the small intestine before the chyme reaches the large intestine
true
