Histology of Digestive System
The Esophagus & Stomach Identification:
The gastroesophageal junction slides can be recognized by the distinct transition of the surface epithelium, from stratified squamous (1) of the esophagus to simple columnar (2) of the stomach.
Features to know:
- Distinguish between the esophagus (left of the pointer in the first slide; above the arrow in the bottom slide) and the stomach (right of the pointer and below arrow).
- Stratified squamous epithelium (1) of the esophagus.
- Simple columnar epithelium (2) of the stomach.
- Note the highly convoluted lining of the stomach, with inward folds forming gastric pits (3).
- Additional layers that are visible include the submucosa (4) and the smooth muscle (5)
The Ileum of the Small Intestine
The ileum (small intestine) slide can be identified by the highly folded (villi) mucosal surface (other parts of the small intestine also have such folds, but no microscope slides of these sections are in lab). The photo at left is at 40x total magnification and shows a section extending from the exterior serosa to interior mucosa. Below is an enlarged view of the mucosal region.
Features to know:
- The innermost (lining the lumen) layer is the mucosa (3).
- The larger folds (which also include part of the submucosa) are called the Plicae Circularis (1).
- The numerous finer folds of epithelium are the villi (2).
- Beneath the mucosa lies an extensive area of areolar connective tissue, the submucosa (4).
- Peyer's Patches (5) are largish, rounded areas located in the submucosa. They can be a bit difficult to spot: look for the slightly darker, purpler color and more speckled or grainy texture.
- The outermost layer of connective tissue is the serosa (8).
- Beneath the serosa are layers of longitudinal (7) and circular (6) smooth muscles.