Histology - Stomach, Small and Large Intestine

Large Intestine - ▪ Enterocytes ▪ Goblet cells

▪ Enteroendocrine cells ▪ M cells (antigen-transport)

NO paneth cells.

Small Intestine

Appendix with prominent GALT - numerous lymphatic nodules.

Oblique, circular, longitudinal layers of muscularis externa in stomach.

Esophagus epithelium - Simple Squamous, Non-Keratinized.

Gastritis in lamina propria (Loose CT inflammation)

Enteroendocrine cells - found at stomach glands, mostly at their base.

Fundus and Body with fundic glands, surface, stem cells, muscous neck cells, parietal cells, chief cells, enteroendocrine cells.

Parietal cells - (HCl secretion) - acidophilic, proton pumps, canaliculi, tubulovescular membranes - secreting acid.

Chief Cells - ABC - apical, basophilic, chief cells

Esophagogastric junction with esophageal cardiac glands - mucus secreting glands in the laminal propria of the lower esophagus.

Enteric nervous system (ENS) - regulates motility, secretion, blood flow. Responds to mechanical, chemical ANS stimuli.

Peyer’s patches - large accumulations of GALT in the lamina propria of ILEUM - may extend into submucosa.

Cardicac Gland - pale, alkaline

Muscularis Mucosae - agitates luminal contents, aids gland expression. Smooth muscle. Same innervation as glands.

Brunner’s glands (or duodenal glands) found in the duodenum which is above the hepatopancreatic sphincter. Produce a mucus-rich alkaline secretion (containing bicarbonate) in order to: protect the duodenum from the acidic content of chyme;
provide an alkaline condition to activarte intestinal enzymes, and lubricate the intestinal walls.

Appendix with mucosa, lamina propria, submucosa, lymphatic nodule

PS is pyloric sphincter - thickening of circular layer of muscularis externa

Appendix - Promitent GALT

Enteroendocrine cells - basal SGs, fundic gland.

Secrete hormones like gastrin, CCK, secretin
Regulate gastric, intestinal, pancreatic, gallbladder activity.

Ileocecal junction

Adhesion of serosa or adventitia. Clinical application, fubrous scar tissue, type 1 collagen.

Large intestine - simple columnar, intestinal glands and goblet cells that secrete mucus for lubrication and protection.

Pyloric Gland

GALT - plasma cells, protection, abundant in ileum and appendix

Rectoanal Junction - Transition from simple columnar to stratified columnar to stratified squamous non keratinized

Top to Bottom - Mucosa, GALT, submucosa, Muscularis externa, serosa

Mucosa, lamina propria. (Loose CT, fenestrated cap, glands, GALT)

Small Intestine - with intestinal folds, villi.

Paneth Cell - epithelium of the small intestine located just below the intestinal stem cells in the intestinal glands (in the crypts of Lieberkühn). Large granules that consist of anti-microbial compounds important in immunity and host-defense.

Stomach - Pylorus - numerous glands

Stomach rugae.

Fundus (or body) of Stomach with surface mucous cells and neck cells - aka Fundic Glands within the lamina propria of fundus and body.

Paneth Cell - epithelium of the small intestine located in the intestinal glands (in the crypts of Lieberkühn). Large granules that consist of anti-microbial compounds important in immunity and host-defense.

Upper third muscularis externa in esophagus. Skeletal swallowing. Lower motor neurons, vagus nerve. neuromuscular synapse, upper esophageal sphincter.

Esophagus - Esophageal glands in submucosa lubricate and protect GI wall from self-digestion.

Intestinal glands (crypts of Lieberkühn) contains multiple types of cells: enterocytes (absorbing water and electrolytes), goblet cells (secreting mucus), enteroendocrine cells (secreting hormones), and at the base, Paneth cells (secreting anti-microbial peptides) and stem cells.

The black bracket is the mucosa; the blue bracket is the submucosa; the red bracket is the muscularis; the green arrow indicates the serosa.

Submucosa - Dense CT aids in supprt, tension. Larger vessels, give rise to capillaries. Submucosal Plexus. Involved in metastasis (lymph vessels) and hemorraging (ulcer).

Stomach

Epithelium: simple columnar

Mucosal glands: fundic, cardiac, pyloric glands

NO submucosal glands.

Small intestine with enterocyte, goblet cell, smooth muscle, and a central lacteal.

Duodenum with Brunner's Glands above the hepatopancreatic sphincter (Sphincter of Oddi). The main function of these glands is to produce a mucus-rich alkaline secretion (containing bicarbonate).

Large Intestine - OL is outer longitundinal folded up to become teniae coli

Large Intestine Mucosa - no villi, plenty of glands in LP. Abundant goblet cells. Similar to small intestine, but NO paneth cells.

Small Intestine with circular folds and villi.

Villus epithelium: ▪ Enterocytes ▪ Goblet cells

Villus lamina propria:
▪ Lacteals: lymphatic capillaries, uptake chylomicrons (modified triglycerides)
▪ Fenestrated (type II) capillaries: uptake of other molecules
▪ Smooth muscle: contract villi; fluid enters lacteals
▪ GALT: immune response

Middle third transition of esophageal muscularis externa.

ENS Myenteric Plexus - regulates peristalsis (muscularis externa)

Muscularis Externa - Myenteric Plexus regulates peristalsis. Clinical - dysmotility and T2 carcinoma.