Stomach Flashcards
What is the function of the stomach?
Digestion
Disinfection
Mechanically disrupt food
Short term food storage
What are the 2 broad categories of GI hormones?
Gastrin family
Secretin family
What hormones are in the gastrin family?
Gastrin
Cholecystokinin
Where is gastrin released from?
G cells in antrum of stomach
What is the role of gastrin?
Increases gastric acid secretion
Where is CCK released from?
I cells in duodenum + jejunum
What is the role of CCK?
Increases pancreatic/gallbladder secretions
What hormones are in the secretin family?
Secretin
Gastric inhibitory polypeptide
Where is secretin released from?
S cells in the duodenum
What stimulates CCK release?
Fat + protein
What stimulates secretin release?
H+
Fatty acids
What is the role of secretin?
Increases HCO3 from pancreas/gallbladder
Decreases gastric acid secretion
Where is GIP released from?
Cells in duodenum + jejunum
What stimulates GIP release?
Sugars
Amino acids
Fatty acids
What is the role of GIP?
Increases insulin
Decreases gastric acid secretion
What are the main parts of the stomach?
Cardia Fundus Body Antrum Greater curvature Lesser curvature Pyloris
What is the cardia?
Where the food enters stomach from oesophagus
What is the fundus?
Superior aspect of the stomach
What is the body?
Main part of the stomach - contains rugae
What are the purpose of rugae?
Folds that expand and increase stomach volume
What is the greater curvature?
Long edge of the stomach - lateral
What is the lesser curvature?
Short edge of the stomach - medial
What is the angularis?
Junction between body and antrum - starts at bottom of lesser curve
What cells are in the gastric pits?
Epithelial cells Mucous cells Parietal cells Chief cells G cells D cells Enterochromaffin like cells
What provides arterial supply to the stomach?
Coeliac trunk
What is the venous drainage from the stomach?
Portal vein
What does the stomach secrete?
HCL
Intrinsic factor
Mucus/HCO3-
Pepsinogen
What do parietal cells secrete?
HCL
Intrinsic factor
What do G cells secrete?
Gastrin
What to ECL cells secrete?
Histamine
What do chief cells secrete?
Pepsinogen
What do D cells secrete?
Somatostatin
What do mucous cells secrete?
Mucous
Where in the stomach are parietal cells found?
Body
Where in the stomach are chief cells found?
Body
Where in the stomach are G cells found?
Antrum
Where in the stomach are mucous cells found?
Antrum
What are parietal cells stimulated by?
Gastrin
Histamine
ACh
How is HCL production stimulated?
Vagus nerve -> release ACh -> acts on parietal cells
ECL cells -> releases histamine -> acts on H2 receptors on parietal cells
Gastrin released by G cells -> acts on CCK receptor on parietal cells
How is HCL production inhibited?
Food leaves stomach -> drop in pH -> D cells release somatostatin -> inhibits G cells
Stomach distension decrease -> drop in vagal activity
PPIs
H2 receptor antagonists
What are G cells stimulated by?
Peptides in stomach
Vagal activity
What inhibits G cells?
Somatostatin
What are the phases of digestion?
Cephalic
Gastric
Intestinal
What stimulates the cephalic stage of digestion?
Parasympathetic stimuli
- smelling/tasting
- vagus nerve stimulates parietal cells
- vagus stimulates G cells
Anticipating food
What stimulates the gastric stage?
Distension of stomach - stimulates vagus nerve
Presence of amino acids/small peptides - stimulate G cells
Food in stomach - removes gastrin secretion inhibition
What stimulates the intestinal stage?
Partially digested proteins in duodenum
- chyme release
- stimulates gastrin
What happens in the intestinal stage?
G cells inhibited
- lipids activate enterogastric reflex
- reduces vagal stimulation
- chyme stimulates CCK and secretin
How does the stomach protect itself from autodigestion?
Mucus - forms thick alkaline layer
High turnover of epithelial cells
Prostaglandins - maintain mucosal blood flow
What can damage the stomach defences?
Alcohol - dissolves mucus layer
H. pylori
NSAIDs - inhibit prostaglandins