GI 2 Flashcards
Stomach
expandable part of GI tract that lies beneath the diaphragm Functions: Storage and digestion of food and regulation of GI function
Rugae
The folds of mucosa and submucosa that allow for the distensible feature of the stomach
Digestion in Stomach
The stomach secretes HCl and digestive enzymes including pepsin and lypase to break down proteins and trigylcerides
How does the stomach regulate GI functions?
Secretion of hormones (eg- gastrin) by enterendocrine cells
Regions of the Stomach
Cardiac Region- located near the esophageal orifice and conatins cardiac glands Fundic Region (inlcudes body)- largest part containing fundic glands Pyloric Region- part proximal to pyloric sphincter containing pyloric glands
Layers of the stomach
mucosa, submucosa, muscularis externa, serosa
Submucosa of Stomach
dense irregular CT containing blood plexus (penetrates mucosa) and nerve plexus (Meissner’s). This layer contains NO GLANDS
Muscularis Externa of the Stomach
3 layers of smooth muscle: Inner oblique layer, middle circular layer, and outer longitudinal layer. Auerbach’s plexus (myenteric nerve plexus) is located between the middle and outer layers of muscle.
Serosa
Mesothelium and thin layer of subserosal CT; makeup same as reg alimentary canal
malignant tumors of stomach
rather common, derived of surface epi cells in assoication with intestinal metaplasia or of glandular epi. Carcinomas are early if they only penetrate submucosa or late if they penetrate muscularis externa or further. The stage directly correlates to outlook of disease.
Muscularis Mucosae of the Stomach (This is still part of the Mucosa)
continuous sheet of smooth mscle with 2-3 layers oriented orthogonally- both circular and longituinal
Lamina Propria of Stomach
loose CT. scant and restricted to space b/n gastric pits and glands. Contains Immune elements like lymphocytes, plasma cells, and MΦ
Pyloric Glands of stomach
in pyloric antrum serving to produce mucus that protects pyloric mucosa. They are branch tubular glands of mucus secretory cells. The gastric pits are often very deep and extend through half the depth of the mucosa. Enteroendocrine cells commonly found interspersed within glandular epithelium.
Cardiac Glands of Stomach
limited to narrow ring surrounding the esophageal orifice. Serve to produce mucus htat contributes to gastric juice and protect esophageal epi against acid reflux. Branched tubular glands of mucus-secreting cells with basally flattend nuclei and granular cytoplasm. They lack parietal and cheif cells, which can differentiate them from Fundic glands. To diff from pyloric, note these glands only extend to half the depth of the mucosa. They also half interspersed enteroendocrine cells.
Progenitor cells
Mostly located in the isthmus of the gland and serve to replace surface mucous cells and fundic gland cells (parietal, chief, mucous neck, and enteroendocrine cells). Short 3-5 day lifespan as compared to fundic gland cells which live 6-8 months
Enteroendocrine Cells
Mostly concentrated at base of gland. Secrete product into lamina propria. Secrete gastrointestinal hormones to regulate functioning of alimentary canal. (including gastrin, ghrelin.) Rest on basement membrane and form microvilli that reach lumen of gland. Filled with membrane bound secretory granules in basilar part of cell.
Gastrin
stimulates gastric acid secretion
Ghrelin
stimulates appetite and hunger perception
What can loss of Paritel Cells cause? When would you expect to see this?
pernicious anemia due to lack of intrinsic factor and thus B12 deficiency. B12 incorporates heme into hemoglobin. Patients with atrophic chronic gastritis.
Gastric Ulcers
impairment of epithelial barrier in the stomach resulting in HCl destroying epi cells and lamina propria. Full penetration of gastric wall allows gastric content to pour into peritoneal cavity and peritonitis
Mucous Neck cells
Mostly found within the neck of the gland. Serve to secrete soluble mucus, which is diff than the insoluble mucus produced by surface mucus cells. They are small and hard to ID. Small heterochromatic nucleus basally placed and cytoplasm of mucinogen granules giving it a frothy appearance.
Gastic Chief Cells
Found at the base of the gland and serve to secrete pepsinogen that converts to pepsin (protelytic enzyme) when in contact with gastric juices. Typically Pt secreting cells. Abundant RER basally, basophilic apperance, apical secretory granules.
Parietal Cells
Mostly found within the neck of gland but also occurs in base. Produce HCl to initiate digestion, convert pepsinogen to pepsin, and destroy bacteria. Produces intrinsic factor needed for absorption of b12 by intestine. LARGEST CELL IN FUNDIC GLAND. STAIN INTENSELY WITH eosin due to MITOCHONDRIA. DISTINCTIVE FEATURE: intracellular cannaliculi with microvilli. These are principal sites of HCL synth and secretion. HCl is toxic so is only produced when needed and in lumen of cannliculi. Apical membrane is nonsecreting stored in tubulovesicular system until stimulated to secrete HCl and fusion with apical membrane and microvilli formation.
What 5 cell types are found in Fundic glands?
parietal cells, gastric chief cells, mucous neck cells, enteroendocrine cells, and progenitor cells
What are the 3 segments of a Fundic gland?
Isthmus, neck and base
Fundic Glands
Found throughout the stomach except small cardiac and pyloric region. They are branched tubular glands extending from muscularis mucosae to base of gastric pits. Straight at middle and apical part and coiled base. Isthmus is apical part adjacent to gastric pit. Base is bottom part adjacent to muscularis mucosae.
Mucosa of Stomach
The lumen of stomach is lined with SCE of surface mucus cells. SMC apical part contains mucinogen granules and produce thick viscous gel coat that adhers to epi surface to protect from chyme abrasion. Within the lamina propria there are many glands unique to the region of stomach that open into gastric pits.
