Stomach and Pancreas Flashcards
What is the peritoneum?
The peritoneum is a serous membrane (continuous membrane that secretes watery fluid) made up of a parietal layer (lines the body wall) and a visceral layer (lines the organs). Between the two layers there is a fluid filled space (peritoneal space)
The retroperitoneal is posterior to the peritoneum and contains organs that don’t need to move (pancreas and duodenum are retroperitoneal organs)
What is the mesentery and the omenta?
The mesentery is a double layer of visceral peritoneum that connects organ to body wall. The omenta is a double layer of visceral peritoneum that connects one organ to another. The lesser omentum connects the stomach to liver which is a single layer and the greater omentum connects the stomach to transverse colon which is a double layer (contains immune cells preventing bacteria)
Where is the stomach located?
The stomach is J shaped organ and is located at the base of the oesophagus. The oesophagus passes through the diaphragm (oesophageal hiatus - gap) hence food passes through oesophagus and empties into stomach. Lower oesophageal sphincter prevents reflux, closes when food is not passing into stomach
What are the 4 key regions of the stomach?
Cardia - part where food goes into first (where oesophagus empties food into first)
Fundus - normally is not filled with food as this is where gas is collected
Body - main section
Pylorus - controls what can pass from stomach into the SI
How is the muscularis modified?
The muscularis is modified for motility and consists of three layers, the oblique layer (innermost), circular layer (middle) and longitudinal layer (outermost)
How is the submucosa modified?
The rugae are temporary folds that allow for the expansion of the stomach (1.5L), core of submucosa which allows it to flatten, important for storage
How is the mucosa modified?
In-folding into mucosa increases SA for secretion - gastric glands. Glands do not flatten. The stomach needs acid and enzymes for digestion, mucous for protection and hormones for regulation
What are gastric glands?
Entrance to glands provided by a ‘gastric pit’, extending from here are simple gastric glands. Mucous epithelial cells secrete mucous for protection, parietal cells secrete acid and intrinsic factor, G cells secrete hormones (gastrin) and chief cells secrete pepsinogen (inactive precursor of pepsin)
What are chief cells?
Chief cells are cells that produce enzymes. They are abundant in the rough endoplasmic reticulum. Apical zymogen granules (contain pepsinogen - inactive version of proteins) and have a basal nucleus
What are Parietal cells?
Parietal cells produce acid, pump H+ ions against its concentration gradient, lots of mitochondria, have a central nucleus, canalicuil (channels between microvilli) and are folded to increase SA
How is the stomach regulated?
Endocrine control occurs in endocrine cells in mucosa, gastric and gherlin are secreted into the bloodstream
Neural control is controlled by ENS (enteric nervous system) which has local reflexes
CNS modulates ENS function - long neural reflexes
Stomach to small intestine
Need controlled release of digested material (chyme) into small intestine
Acidic chyme enters small intestine, requires further digestion (enzymes) and protection from acidic chyme (mucous and neutralise acid). Mucous provided by glands in submucosa of the duodenum. Enzymes and bicarbonate provided by pancreas
What is the pancreas?
Pancreas is a retroperitoneal organ, head sit in towards C-shaped duodenum, tail to spleen, posterior to stomach, duct into duodenal lumen
Secretions travel through duct down and mix with secretions (bile) from liver and gall bladder, important for fat digestion, released out of duodenal papilla into the duodenum where acid is neutralised
What are the endocrine and exocrine functions of the pancreas?
Endocrine function: pancreatic islet alpha cells secrete glucagon and pancreatic islet beta cells secrete insulin
Exocrine function: acinar cells secrete digestive enzymes and duct cells secrete bicarbonate
What are acinar cells?
Apical zygogen granules, basal nucleus, abundant in rough ER, similar to chief cells. Function to secrete enzymes, exocytosing them into duct which are secreted into pancreatic duct
