No abstract

The anal canal is an important body part clinically. However, there is no agreement about the epithelium of the anal canal, the anal transitional zone (ATZ) epithelium in particular. The aim of this study is to clarify the structure of the epithelium of the human lower rectum and anal canal. Intact rectum and anus obtained from patients who underwent surgery for rectal carcinoma were examined by light and scanning electron microscopy (LM and SEM). By LM, three types of epithelium were observed in the anal canal: simple columnar epithelium, stratified squamous epithelium, and stratified columnar epithelium. The lower rectum was composed of simple columnar epithelium. SEM findings showed stratified squamous epithelium that consisted of squamous cells with microridges, changing to simple columnar epithelium consisting of columnar cells with short microvilli at the anorectal line. LM and SEM observations in a one-to-one ratio revealed that the area of stratified columnar epithelium based on LM corresponded to the anal crypt and sinus. In conclusion, the epithelium of the human anal canal was fundamentally composed of simple columnar epithelium and stratified squamous epithelium. We found no evidence of the ATZ.

The aim of the present study was to clarify the anatomical structure of the lamina muscularis mucosae (LMM) in the human stomach and to correlate it with the lymphatic spread of gastric cancer cells. Human stomachs taken at operation or autopsy were used. The specimens derived from these stomachs were examined by light microscopy immunohistochemistry and scanning electron microscopy (SEM). In the cardia and pyloric wall, bundles of smooth muscle cells of the LMM were relatively loose and thin and formed a reticular configuration. Small lymphatic capillaries (approximately 10-30 μm in diameter) were present directly above the LMM, and relatively large lymphatics (approximately 80-100 μm in diameter) were observed in the submucosal layer and within the LMM. In contrast, the LMM in the fundus, body, and antral wall was composed of tight, thick bundles of smooth muscle cells that ran straight. Large lymphatics were found directly beneath the LMM, but they were few in the lamina propria mucosae. In addition, lymphatics adjacent to veins were also found in the submucosa of the fundus. Structural differences in the LMM of the stomach wall might depend on physiological function. In this study, the relationship between the cytoarchitecture of the LMM or the distribution of lymphatic vessels and cancer invasion is discussed.

Morphological studies examined communication routes between the epithelium and lamina propria mucosae in the human esophagus, using a series of techniques including silver staining, immunohistochemistry, transmission electron microscopy, and scanning electron microscopy (SEM). For SEM, tissue blocks were treated with either osmium/ultrasonication or NaOH. Observations showed the esophageal papillae to be arranged regularly in a mostly longitudinal row. The reticular fibers, consisting of fibrils approximately 40 nm in diameter, were situated just beneath the epithelial basal lamina. They showed a positive reaction with a type III collagen antibody, and formed a continuous sheet 2-3 microm thick with dense networks. This sheet as well as the epithelial basal lamina had numerous foramina of diameters of 3-5 microm. Immune cells such as lymphocytes and Langerhans cells were situated around these foramina. The foramina were situated both around papillae and the duct orifice of the esophageal gland. In addition, lymphoid follicles surrounded the duct of the esophageal gland. The structural characteristics around the duct appear to be those of duct-associated lymphoid tissue (DALT). Thus, these foramina in the epithelial basal lamina and reticular fiber sheet may represent important communication routes between the epithelium and lamina propria mucosae. In addition, they may play an important role in the mucosal immune response in the human esophagus.

The structural organization of the lamina muscularis mucosae of the human esophagus was studied by light microscopy and scanning electron microscopy (SEM). The organization of the lamina muscularis mucosae varied considerably among the cervical, the thoracic, and the abdominal part of the esophagus. In the cervical part, the lamina muscularis mucosae was not well developed and only islets of the smooth muscle bundles were scattered within the connective tissue. In the thoracic part, the lamina muscularis mucosae consisted of several layers of smooth muscle bundles, individual muscle cells of which ran in a longitudinal direction. In the abdominal esophagus near the cardia, the muscular bundles in the lamina muscularis mucosae ran in various directions forming a reticular configuration. The differences in density and arrangement of the lamina muscularis mucosae are discussed in relation to the swallowing of food and submucosal invasion of esophageal cancer.