Gastroesophageal Junction Anatomy

Study Notes

Muscularis externa has three layers of muscle cells, unlike the two layers found elsewhere in the GI tract.
The inner oblique layer is unique to the stomach and is found near the boundary with the submucosa.
The middle circular layer and outer longitudinal layer are also present.

The cardiac stomach is the closest to the esophagus and contains mucus-secreting glands.
It is the narrow region surrounding the opening of the esophagus that contains cardiac glands in the mucosa.
The epithelium structure abruptly changes from stratified squamous non-keratinized (esophagus) to simple columnar (stomach).

Cross-sections of gastric pits and cardiac glands can be distinguished by their location and cell type.
Gastric pits are closer to the surface and have smaller, surface mucous cells.
Cardiac glands are closer to the muscularis mucosae and have larger, mucous-secreting cells.

The fundic stomach is the largest part of the stomach (body/fundus) and contains fundic (gastric) glands.
It has folds or ridges called rugae, formed from the mucosa and submucosa.
The mucosa is composed of the epithelium, lamina propria, and muscularis mucosae.
Gastric pits are surface invaginations lined with surface mucous cells.

The fundic glands have three major regions: isthmus, neck, and fundus.
The isthmus is a small region at the apex of the gland adjacent to a gastric pit.
The neck is the largest part of the gland between the isthmus and the fundus.
The fundus is the base of the gland adjacent to the muscularis mucosae.
The glands contain three major cell types: mucous neck cells, parietal cells, and chief cells.

The pyloric stomach is closest to the small intestine and contains mucus-secreting glands.
It forms the distal region of the stomach that opens into the small intestine.
The mucosa is composed of the epithelium, lamina propria, and muscularis mucosae.
Pyloric glands appear as cross-sections of the short, coiled tubular glands of only mucous secreting cells.

The small intestine does not have villi, but has folds or ridges called plicae circularis (or valves of Kerckring).
The mucosa is composed of the epithelium, lamina propria, and muscularis mucosae.
Absorptive cells (or enterocytes) have microvilli (or brush border) to expand the absorptive surface.
Goblet cells secrete mucus for lubrication.
Crypts are intestinal glands found at the base of villi.

The anal canal is the site where there is a transition from the simple columnar epithelium of the colon to the stratified squamous epithelium of skin.
The colorectal zone is on the left side of the specimen.
Anal glands secrete mucus into the anal canal.
The internal anal sphincter is an expansion of the inner circular layer of the muscularis externa.
The pectinate line (anal transition zone) is the junction between the simple columnar epithelium of the colon and the stratified squamous epithelium of the skin.
The squamous zone of the anal canal is on the right side of the specimen.
The external sphincter is a skeletal muscle that is part of the pelvic floor.
Circumanal glands are apocrine glands.