KEY Adv, adventitia Ep, stratified squamous epithelium L, longitudinal layer of muscularis externa LP, lamina propria LV, lymphatic vessels Lym, lymphocytes ME, muscularis externa MM, muscularis mucosae Muc, mucosa SM, smooth muscle StM, striated muscle SubM, submucosa arrows (upper figure), lymphocytes in epithelium asterisks (lower figure), areas containing striated muscle in the muscularis externa
PLATE 55 Esophagus And Stomach, Cardiac Region
The esophagogastric junction marks a change in function from that of a conduit (esophagus) to that of a digestive organ (stomach). The epithelium of the mucosa changes from stratified squamous (protective) to a simple columnar secretory epithelium that forms mucosal glands that secrete mucinogen, digestive enzymes, and hydrochloric acid. The very cellular lamina propria is rich in diffuse lymphatic tis-sue, emphasizing the role of this layer in the immune system.
Esophagogastric junction, esophagus-stomach, human, H&E ×100.
The junction between the esophagus and stomach is shown here. The esophagus is on the right, and the cardiac region of the stomach is on the left. The large rectangle marks a representative area of the cardiac mucosa seen at higher magnification in figure below; the smaller rectangle shows part of the junction examined at higher magnification in figure on right. As noted in Plate 54, the esophagus is lined by stratifed squamous 608 epithelium (Ep) that is indented on its undersurface by deep connective tissue papillae. When these are sectioned obliquely (as five of them have been), they appear as islands of connective tissue within the thick epithelium. Under the epithelium are the lamina propria and the muscularis mucosae
Cardiac region, stomach, human, H&E ×260.
The cardiac glands and pits seen in top figure are surrounded by a very cellular lamina propria. At this higher magnification, it can be seen that many cells of the lamina propria are lymphocytes and other cells of the immune system. Large numbers of lymphocytes (L) may be localized between the smooth muscle cells of the muscularis mucosae (MM ), and thus, the muscularis mu cosae in these locations appears to be disrupted.
Cardiac region, stomach, human, H&E ×440.
The epithelium of the cardiac glands (GL ) also consists of mucous gland cells (MGC ). As seen in the photomicrograph, the nucleus of the gland cell is typically flattened; one side is adjacent to the base of the cell, while the other side is adjacent to the pale-staining cytoplasm. Again, mucus is lost during processing of the tissue, and this accounts for the pale-staining appearance of the cytoplasm. Although the cardiac glands are mostly unbranched, some branching (MM ). At the junction between the esophagus and the stomach (see also middle right figure ), the stratified squamous epithelium of the esophagus ends abruptly, and the simple columnar epithelium of the stomach surface begins.
The surface of the stomach contains numerous and relatively deep depressions called gastric pits (P ), or foveolae, that are formed by epithelium similar to, and continuous with, that of the surface. Glands (GL ) open into the bottom of the pits; they are cardiac glands. The entire gastric mucosa contains glands. There are three types of gastric glands: cardiac, fundic, and pyloric. Cardiac glands are in the immediate vicinity of the opening of the esophagus; pyloric glands are in the funnel-shaped portion of the stomach that leads to the duodenum; and fundic glands are throughout the remainder of the stomach.