Histology - Esophagus and stomach

Pernicious anemia

Lack of GIF results in lack of B12 uptake, which inhibits RBC production

Parietal cells

Large, acidophilic cells in upper 1/2 of glands. Contain intracell. canaliculi and abundant mitochondria. Produce H+ and HCO3- via carbonic anhydrase (A)

Undifferentiated stem cells

Located at base of pits and in neck of glands, provides for renewal of surface epithelium every 3-5 days. Cells in glands renewed every 180 days.

Cardiac glands

Located in cardiac region of stomach. Contain primarily mucous cell - mucus protects esophageal epithelium. Also contains enteroendocrine cells, mucous neck cells, and undifferentiated stem cells. Empty into short gastric pits in shallow mucosa.

Mucous neck cells

Located in upper part of gastric glands, different than surface mucous cells. Produce characteristic soluble mucinogen (A)

Gastric glands

Major type of mucosal gland, found in fundic stomach. Produces gastric juice. Characteristic 2-tone staining appearance in H&E 2/2 multiple cell types

Mucosal or cardiac glands

May be present near end of esophagus in lamina propria, simple branched tubular glands similar to those in cardiac region of stomach.

Submucosa of digestive system

Dense irreg. CT w/ BVs, lymphatic vessels, and nerves Contains ganglion cells of submucosal (Meissner's) plexus Contains glands in esophagus and duodenum only

Mucosa of stomach

Epithel. - simple columnar, surface and gastric pits lined w. surface mucous cells - mucous film has high bicarb content to protect epithel. from acidity Lamina propria - loose CT in between mucosal glands, with BVs, lymphocytes, plasma cells, eosinophils, mast cells, and macrophages Muscularis mucosae - sends smooth muscle cells in between glands to help empty

Esophagogastric junction

Epithelium changes from stratified squamous to simple columnar

Inactive parietal cells

Exhibit increase in cytoplasmic tubulovesicular membrane system, canaliculi retracted back into cytoplasm.

Histamine (H2) receptor antagonist

I.e. Zantac, used to treat heartburn

Pyloric glands

In pyloric region of stomach. Empty into long gastric pits, glands contain primarily mucous cells that secrete mucus to protect pyloric mucosa and lysozyme (anti-basterial). Also contains enteroendocrine cells (gastrin cells concentrated here), mucous neck cells, undifferentiated stem cells. Lamina propria surrounding these glands contains more lymph tissue.

Gastric pits

Indentations in mucosa. Mucosal glands empty into this.

Pepsinogen

Activated from zymogen form by acidic gastric juice to form pepsin - initiates protein digestion. Made by chief cells. (made by B)

Mucosa of digestive system

*Epithelium - protective, secretory, or absorptive; either stratified squamous nonkeratinized or simple columnar *Lamina propria - loose CT w/ many capillaries, contains gut associated lymphatic tissue (GALT), may contain mucosal glands *Muscularis mucosae - thin layer of smooth muscle, usually inner circular and outer longitudinal

Muscularis externa and serosa of stomach

3 layers of smooth muscle - inner oblique, middle circular, outer longitudinal; contractions churn and homogenize food. Myenteric plexus found b/w circular and longitudinal layers. Serosa - loose CT covered w/ mesothelium

Chief cells

Basophilic cells in lower part of glands, typical protein secretory cells (granules, lots of rER, prominent Golgi) that produce pepsinogen granules which are concentrated apically

Submucosal glands

Compound tubuloalveolar glands. Mostly mucous cells but some serous cells producing lysozyme. Found in submucosa of esophagus and duodenum.

Esophagus

Mucosa - SSNK epithelium; lamina propria w. loose CT and mucosal/cardiac glands near end of esophagus; muscularis mucosae is single layer of long. smooth muscle Submucosa - Dense irreg. CT, submucosal glands present Muscularis externa - inner circ. and outer long. layer, transition from skeletal m. (upper 1/3) to smooth m. (lower 1/3) Adventitia - loose CT blends w/ adj. structures

Oropharynx

Mucosa - epithelium is stratified squamous non-keratinized; lamina propria is loose CT w/ elastic fibers, some mucous glands, prominent elastic layer that sends fibers into muscle layer Submucosa not present Muscularis externa - inner circular and outer longitudinal layer of skeletal muscle Adventitia - tough fibroelastic CT

Submucosa of stomach

No glands! Dense irreg. CT, nerves and ganglion cells of submucosal (Meissner's) plexus present

Alimentary canal

Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal

Serosa

Outermost layer of CT covered by simple squamous epithelium called mesothelium - if organ is suspended in peritoneal cavity

Adventitia (fibrosa)

Outermost layer when organ is not suspended in peritoneal cavity, no mesothelium

Helicobacter pylori

PRoduces ammonia via urease which neutralizes acid and allows bacteria to survive. Epithel. is then destroyed and results in gastric ulcers w/ bleeding. This bacteria also promotes production of excess stomach acid - believed to increase gastrin by inhibiting somatostatin producing cells.

Gastrin cells

Primary enteroendocrine cell in the stomach. Concentrated in pyloric region, main fxn is to stimulate production of HCl via parietal cells. Inhibited by somatostatin

Gastric Intrinsic Factor (GIF)

Produced by parietal cells, it is a glycoprotein which complexes w/ B12 so it can be absorbed in the small intestine -> important in RBC production

Endocrine products made in small intestine but functioning in stomach

Secretin and gastric inhibitory peptide (GIP) which both inhibit gastric acid secretion Motilin - increases gastrointestinal motility

Mammillated or gastric areas

Small, bulging areas with thickened mucosa. Provide increased SA for secretion

Rugae

Temporary longitudinal submucosal folds, causing mucosa to fold, that accommodate expansion of stomach.

Ganglia of myenteric (Auerbach's) plexus

This and submucosal plexus belong to intrinsic enteric component of autonomic nervous system. Regulate peristaltic muscular contractions and secretory functions of mucosal and submucosal glands.

Principal organs associated with alimentary canal

Tongue, teeth, salivary glands, pancreas, liver, and gallbladder

Active parietal cells

Tubulovasicular membranes w/ H+, K+ ATPase fuse w/ plasma membrane -> increasing canaliculi. H+ and Cl- released into gland lumen, NaHCO3 released concurrently into underlying lamina propria. Secretion of H+ and Cl+ stimulated by gastrin, acetylcholine, and histamine.

Enteroendocrine cells

Typically found singly throughout gland. Exhibit basal granules for release into lamina propria. Hormones (released via merocrine) can act in paracrine or true endocrine manner. Those that contact lumen are open type, those that don't are closed. Cells can respond to pressure, luminal content, or neuroendocrine stimulation. Some stain w/ silver/dichromate salts => designated as argentaffin, argyrophilic, or chromaffin cells. Cells in GI tract coordinate gastric function.

Muscularis externa

Usually 2 muscle layers - inner circular and outer longitudinal (in stomach there is also inner oblique layer), which provide for luminal and longitudinal constriction Composed of smooth muscle except in esophagus and end of anal canal (skeletal muscle), also contain ganglia of myenteric (Auerbach's) plexus