stomach - physiology + disease Flashcards
what is the function of the stomach (4)
stores/churns food
continues the digestion of carbohydrates
initiates digestion of protein
regulates the delivery of chyme
name the main anatomical regions of the stomach
lower oesophagus sphincter fundus body antrum greater and lesser curve pylorus/pyloric sphincter
what are the two sphincters associated with the stomach
lower oesophagus sphincter (LOS)
pyloric sphincter
what are the two types of glands within the stomach
PGA = pyloric gland area OM = oxyntic mucosa
what is the location of the pyloric gland area
antrum
what is the location of the oxyntic mucosa
body and fundus
what cells are found in the oxyntic mucosa
D cells and G cells
what cells are found in the pyloric gland area
parietal cells, chief cells, and entrochromaffin-like cells
what is produced in the oxyntic mucosa
HCL
pepsinogen
intrinsic factor & gastroferrin
histamine
what is produced in the pyloric gland area
somatostatin
gastrin
what does gastrin do
stimulates HCL secretion
where is gastrin produced and by what cells
G cells in the pyloric gland area
what does somatostatin do
inhibits HCL secretion
where is gastrin produced and by what cells
D cells in the pyloric gland area
what does HCL do
activates pepsinogen to pepsin
denatures proteins
where is HCL produced and by what cells
parietal cells in the oxyntic mucosa
what does pepsinogen do
inactivate precursor to pepsin
where is pepsinogen produced and by what cells
chief cell in the oxyntic mucosa
what does histamine do
stimulates secretion of HCL
where is histamine produced and by what cells
entrochromaffin-like cells in the oxyntic mucosa
what does in the intrinsic factor and gastroferrin
binds to B12 to allow absorption in terminal ileum
where are intrinsic factor and gastroferrin produced and by what cells
parietal cell in the oxyntic mucosa
what does parietal cells produce
HCL
intrinsic factor and gastroferrin
what does chief cells produce
pepsinogen
what does entrochromaffin-like cells produce
histamine
what does D cells produce
somatostatin
what does G cells produce
gastrin
what determines the passage of chyme
the strength of the astral wave
what are the 3 phases of gastric acid secretion
cephalic phase
gastric phase
intestinal phase
when does the cephalic phase take place
before food reaches the stomach, prepares it to receive food
how is the cephalic phase driven
directly and indirectly by the CNS and vagus nerve (CNX)
when does the gastric phase take place
when food is in the stomach
when does the intestinal phase take place
after food has left the stomach
what stimulates the intestinal phase
chyme entering the upper small intestine via neuronal and hormonal mechanisms (WEAK stimulation)
how is are gastric secretions in the cephalic phase inhibited
vagal nerve activity decreased upon cessation of eating and following stomach emptying
(pain, nausea and negative emotions also decrease vagal activity)
how are the gastric secretions in the intestinal phase inhibited
via the same methods that reduce gastric motility
how are the gastric secretions in the gastric phase inhibited
antral pH falls when food leaves the stomach causing somastostain release from D cells
how is the mucosa protected from HCL and pepsin
located produced prostaglandins: PGE2 and PGI2
what do prostaglandins PGE2 and PGI2 do
reduce acid secretion
increase mucus and bicarb secretion
increase mucosal blood flow
what causes acute gastritis
⇒ irritant chemical injury ⇒ Severe burns ⇒ Shock ⇒ Severe trauma ⇒ Head Injury
what are the 3 causes of chronic gastritis
autoimmune (rare)
bacterial/H.pylori (most common)
chemical
what is the cause of autoimmune chronic gastritis
anti-parietal and anti-intrinsic factor antibodies
what is the main symptom of autoimmune gastritis
pernicious anaemia
what causes pernicious anaemia
B12 deficiency
what causes chemical chronic gastritis
NSAIDs
alcohol
bile reflux
describe what happens in chemical chronic gastritis
direct injury to mucus layer by fat solvents leading to marked epithelial regeneration, hyperplasia, congestion and little inflammation
