Lecture 21: STOMACH AND PANCREAS Flashcards
What is the shape of the stomach?
J-shaped organ
Where is the stomach located?
At the base of the esophagus
What does the esophagus pass through?
The diaphragm at the oesophageal hiatus
What does the lower oesophageal sphincter do?
Prevent reflux. Relaxes to let food through and contracts to prevent reflux
What are the main parts of the stomach?
Cardia, fundus, body and pylorus (pyloric antrum)
What does the lesser omentum do?
Connects the lesser curvature of the stomach to the liver
What does the greater omentum do?
Connects the greater curvature of the stomach to the transverse colon
What does the greater omentum contain?
Blood vessels, fat and immune cells
What is the muscularis of the stomach modified for?
Motility
What are the layers of the stomach muscularis?
Oblique (inner), circular (middle) and longitudinal (outer)
What is the thickness of the muscularis of the stomach?
Thicker in the pylorus (distal) compared to the cardia (proximal) as there is more mechanical digestion here
What are rugae?
Temporary folds that allow for the expansion of the stomach
What volume can the stomach expand to?
1.5L
What is the rugae important for?
Storage, as well as the sphincters
What is the structure of rugae?
They have a folded core of submucosa with overlying mucosa
What is the epithelium of gastric gland mucosa?
Simple columnar
What does folding of the gastric gland mucosa do?
Increase surface area for secretion (3L/day)
What are gastric glands?
Permanent
Where re gastric glands found?
In the mucosa only
What do we need from the gastric glands?
Acid and enzymes for digestion, mucous for protection and hormones for regulation of secretory and motility events
What cells are in the gastric pits?
Goblet cells
What do the goblet cells do?
Secrete mucous for protection
What cells are in the gastric glands?
Parietal cells, G cells and chief cells
What do parietal cells do?
Secrete acid (particularly HCl) and intrinsic factor (important for vitamin B12 absorption)
What do G cells do?
Secrete hormones (gastrin)
What do chief cells do?
Secrete pepsinogen (an inactive precursor of pepsin which digests proteins)
What do chief cells produce?
Enzymes
What is abundant in chief cells?
Rough endoplasmic reticulum (as making proteins)
What is apical in chief cells?
Zymogen granules (contain enzymes to be exocytosed)
What is basal in chief cells?
Nucleus
What do parietal cells produce?
Acid
What is abundant in parietal cells?
Mitochondria
What do parietal cells do?
Pump hydrogen ions
Where is the nucleus of parietal cells?
central
Why is the parietal cell membrane folded?
To increase surface area for ion pumps for secretion
What is the endocrine control of the stomach?
Endocrine cells of mucosa, gastrin and ghrelin secreted into the bloodstream
What is the neural control of the stomach?
enteric nervous system (ENS) - local reflexes (primary control), CNS modulates ENS function- long neural reflexes
What is needed between the stomach and small intestine?
Controlled releasee of digested material (chyme)
How is controlled releasee into the SI achieved?
Pyloric sphincter
What does acidic chyme do?
Enter the small intestine
What is required from the stomach to small intestine?
Further digestion and protection from acidic chyme (mucous and neutralise acid)
How is mucous provided?
By glands in the submucosa of the duodenum
How is acid neutralised?
Enzymes and bicarbonate provided by pancreas
What is the shape of the pancreas?
Round head in c shaped duodenum
Where is the tail of the pancreas?
To the spleen
What is the pancreas posterior to?
The stomach
What does the pancreas have a duct into?
The duodenal lumen (bile duct + pancreatic duct = duodenal papilla)
Where is the pancreas found?
Retroperitoneal
Where does the bile duct meet the pancreatic duct?
At the entrance to the hepatopancreatic ampulla
What does the duodenal papilla do?
Project into the duodenal lumen
What is release into the pancreas controlled by?
Hepatopancreatic sphincter
What does endocrine mean?
inside, into blood
What is the endocrine function of the pancreas?
Pancreatic islet alpha cells secrete glucagon and pancreatic islet beta cells secrete insulin
What is the exocrine function of the pancreas?
Acinar cells secrete digestive enzymes and duct cells secrete biacrbonate
What does exocrine mean?
Outside, into the GI tract
What is the structure of pancreatic acinar cells?
Apical zymogen granules, basal nucleus and abundant rough ER
What is the function of pancreatic acinar cells?
Secrete enzymes
