The Stomach and Pancreas Flashcards
Describe the peritoneum
The perineum is a serous membrane that lines the abdomen
- Parietal layer: lines the body wall
- Visceral layer: covers the organs
Between these layers is a fluid filled space
Retroperitoneal: posterior to the peritoneum (organs that are not in the peritoneum but are covered by it on one side, they are organs that don’t move very much)
What are the mesenteries and omenta?
- Peritoneum: serous membrane
- Mesentery: Double layer of visceral peritoneum that connects organ to body wall
- connects small intestine to body wall
- Omenta: double layer of visceral peritoneum that connects an organ to another organ
- Omentum (singular)
- lesser omentum connects liver and stomach
- greater omentum connects stomach and transverse colon
Describe the location of the stomach
- J-shaped organ
- Located at the base of the esophagus and leads to the small intestine (duodenum - first part of small intestine)
- Quite high up in the abdomen
- Esophagus passes through diaphragm (hole called esophageal hiatus)
- Lower esophageal sphincter (LES) prevents reflex (closes to stop acid from splashing up into esophagus when food isn’t coming into stomach)
Describe the four main parts of the of the stomach and what holds it in place
4 Main parts:
- Cardia: closest to the heart but doesn’t touch it
- Fundus: broad part at the top of the stomach, usually doesn’t fill with food but instead gas
- Body - where most of the stuff happens
- Pylorus (pyloric antrum): gate-keeper (gate-keeps the digestive food of the stomach, deciding if it is allowed to go into the small intestine)
Held in place by the omenta:
- Lesser omentum: stomach to liver
- Greater omentum: stomach to transverse colon
Describe the modifications to the muscularis of the stomach
Muscularis
- modified for motility
Has three layers instead of two to help churn up food:
- Oblique (inner)
- Circular (middle)
- Longitudinal (outer)
Describe the modifications to the submucosa of the stomach
- Rugae are TEMPORARY folds in the submucosa that allow for the expansion of the stomach (so that it doesn’t pop)
- Core of submucosa
- Important for storage
Describe the modifications to the mucosa of the stomach
- Simple columnar epithelium
- In-folding increases surface area of secretions (so can have lots of secretions produced) - gastric glands
- Glands do not flatten
The stomach needs:
- Acid and enzymes for digestion
- Mucous for protection
- Hormones for regulation
Gastric glands:
- Gastric pits (closest to the surface so that mucus is secreted onto surface of organ for protection)
- Mucous epithelial cells: secrete mucous (protection)
- Gastric glands (under gastric pits)
- Parietal cells: secrete acid for intrinsic factor
- G cells: secrete hormones (gastrin)
- Chief cells: secrete pepsinogen (an inactive precursor of pepsin - inactive so it doesn’t digest these cells)
Describe stomach cell histology for chid cells and parietal cells
Chief cells: produce enzymes
- Abundant rough ER
- Apical zymogen granules (contains pepsinogen)
- zymogen is short for secretory vesicle with inactive enzyme, exocytoses pepsinogen
- Basal nucleus
Parietal cells: produce acid
- Pump ions (H+)
- Abundant mitochondria (pumping ions against conc. gradient so using lots of energy, therefore needs lots of mitochondria to make more energy
- Central nucelus
- Folded structure to increase surface area
- Canaliculi (channels between microvilli for H+ ions to move through)
- Microvilli (fill up internal spaces for more surface area
Describe the regulation of stomach function
Endocrine control:
- Endocrine cells in mucosa
- Gastrin and Ghrelin secreted into the bloodstream
Neural control:
- Enteric nervous system (END) - local reflexes (primary control)
- CNS modulates END function - long neural reflexes
Describe what the pyloric sphincter does
Need controlled release of digested material (chyme) into the small intestine, pyloric sphincter controls this
Describe what happens once acidic chyme enters the small intestine
Requires:
- Further digestion (enzymes)
- Protection form acidic chyme
- Mucous
- Neutralise acid
- Mucus provided by glands in the submucosa of the duodenum
- Enzymes and bicarbonate (neutralise acid) provided by pancreas
Describe the location of the pancreas
- Retroperitoneal
- Head in C-shaped duodenum
- Tail to spleen
- Posterior to the stomach
- Duct into duodenal lumen
Describe the endocrine and exocrine functions of the pancreas
Endocrine:
- Pancreatic islet alpha cells secrete glucagon
- Pancreatic islet beta cells secrete insulin
Exocrine:
- Acinar cells secrete digestive enzymes
- Duct cells secrete bicarbonate
Describe the structure and function of pancreatic acinar cells
Structure:
- Apical zymogen granules
- Basal nucleus
- Abundant rough ER
Function:
- Secrete enzymes
Describe the ducts of the pancreas and how they are controlled
- Bile duct meets pancreatic duct at the entrance of the hepatopancreatic ampulla
- bile is essential for fat digestion
- Bile duct runs close to the pancreas and intestine and merges with the pancreatic duct into the hepato(liver)pancreatic(pancreas) ampulla - Duodenal papilla - projects into the duodenal lumen (this is how it gets into the duodenum)
- Release controlled by hepatopancreatic sphincter
