The Stomach Flashcards
what are the 3 regions of the stomach?
the cardia, fundus and antrum
what do parietal cells do
produce HCl
what stimulates parietal cells
gastrin, histamine and ACh (from the vagus nerve)
what receptors does gastrin act n to activate parietal cells
CCK receptors
what receptors does histamine act on to activate parietal cells
H2 receptors
what receptors does Ach act on to activate parietal cells
Mcr receptors
what is the alkaline tide
during H+ production in the parietal cells, bicarb is also produced, which moves into the blood vessels draining the stomach making the blood here temporarily more alkaline
why do parietal cells require lots of mitochondria
they need lots of energy to use the proton pump against a large concentration gradient
what do chief cells do
produce pepsinogen
what stimulates chief cells
gastrin via the CCK receptor
vagus nerve Ach via the Mcr receptor
what do G cells produce
gastrin
what stimulates G cells
vagus nerve secreting ACh
amino acids in the stomach
what does gastrin do
activate parietal cells
what inhibits gastrin production
somatostatin
what do enterochromaffin cells do
secrete histamine
what stimulates ECL cells
gastrin via the CCK receptor
vagus Ach via the Mcr receptor
what role does histamine have in the stomach
activates parietal cells
what do D cells do
secrete somatostatin
what does somatostatin inhibit in the stomach
G cells and ECL cells
what are the roles of stomach acid
- part of the innate immune system
- chemical digestion
- converts pepsinogen into pepsin
what types of cells are mostly found in the cardia of the stomach
mucus secreting cells
what types of cells are mostly found in the Antrum of the stomach
G cells and D cells
what type of cells are mostly found in the fundus/body of the stomach
mucus secreting cells, parietal cells, chief cells
what does the stomach do to help protect itself
- bicarbonate rich mucus secretion
- prostaglandins
- high turnover of epithelia
what do prostaglandins do in the stomach
increase blood flow to the stomach - this brings more nutrients to the epithelia
what inhibits prostaglandin productions
NSAIDs like aspirin
how does alcohol affect the stomach
dissolves the mucus layer
what are the 3 phases of digestion in the stomach
cephalic
gastric
intestinal
what happens in the cephalic phase of digestion
the smell and chewing of food stimulates parietal and G cells though the vagus nerve
what happens in the gastric phase of digestion
stomach distension activates parietal and G cells (through the vagus nerve)
amino acids activate G cells
enteric NS causes smooth muscle contractions
what happens in the intestinal phase of digestion
chyme in the duodenum stimulates gastrin production before the G cells become inhibited
what stimulates D cells
when food leaves the stomach, the pH drops as it is no longer being buffered
the lower pH activates the D cells
what test can be done to diagnose h-pylori
urease breath test
what does the urease enzyme do
converts urea into ammonium
how can urease damage the stomach
the ammonium produced is directly toxic to cells
how does h-pylori cause damage
- through ammonium production which is toxic
- is cytotoxic to the epithelia itself
if h-pylori is found in the Antrum what will it cause
duodenal ulceration
if h-pylori is found in the body what will it cause
stomach cancer
give an example of a proton pump inhibitor
omeprazole
give an example of a H2 antagonist
cimetidine
what ways are there to treat stomach problems
proton pump inhibitors
H2 antagonists
stop NSAIDs
antibiotics for H-pylori
what is GORD
where the stomach contents moves into the oesophagus
what causes GORD
lower oesophageal sphincter problems
obesity
hiatus hernia (upper stomach into the thorax)
delayed stomach emptying (increase intra-gastric pressure)
what symptoms are seen in GORD
heart burn
cough
sore throat
dysphasia
what is Barrett’s oesophagus
where reflux causes metaplasia of the stratified squamous epithelia of the oesophagus to convert into simple columnar - increasing the risk of adenocarcinoma
how do you treat GORD
antacids
H2 antagonists
proton pump inhibitors
what is gastritis
inflammation of the lining of the stomach
what may cause acute gastritis
heavy NSAID use, alcohol, chemotherapy
what may cause chronic gastritis
h-pylori, autoimmune disease attacking parietal cells
why may an autoimmune disease against parietal cells cause anaemia
as parietal cells produce intrinsic factor which helps in vitamin B12 absorption - without vitamin B12 you will develop anaemia
what type of anaemia is developed from a lack of vitamin B12
pernicious anaemia
what is peptic ulcer disease
where the mucosa is eroded down through the muscularis mucosa layer
what may cause peptic ulcer disease
NSAIDs, h-pylori, stomach acid
what are the symptoms of peptic ulcer disease
epigastric pain, weight loss, bleeding (if a vessel is eroded through)
why may you get epigastric pain with peptic ulcers
as the stomach is a foregut structure
what is Zollinger-Ellison disease
where theres a gastrin secreting tumour - this causes an up regulation of parietal cells causing increased acid production
what can happen to the small intestine as a result of Zollinger Ellison
can lead to holes in the small intestine
what can cause stress ulcers
burns, sepsis, trauma, multi organ failure
when does acid production increase
when amino acids/peptides are detected in the stomach lumen and when the stomach is distended
how will H. pylori appear on a gram stain
gram negative helix shaped bacteria
how does the mucus layer help protect the stomach
it is strongly alkali so protects it from the acidic conditions
where are the cells of the stomach located
within the gastric pits of the stomach
why does the pyloric sphincter strongly control what it lets through
in order to ensure it doesn’t overflow the duodenum with liquid chyme as it is still highly acidic
how does receptive relaxation prevent reflux
vagally mediated relaxation allows food to enter stomach without raising gastric pressure
