The anal canal is located within the anal triangle of the perineum between the right and left ischioanal fossae. It is the final segment of the gastrointestinal tract, around 4cm in length. The canal begins as a continuation of the rectum , and passes inferoposteriorly to terminate at the anus. Except during defecation, the anal canal is collapsed by the internal and external anal sphincters to prevent the passage of faecal material. It is formed by the fusion of the internal anal sphincter, external anal sphincter and puborectalis muscle, and is palpable on digital rectal examination.
Histology of the anal canal.
Anal canal - Wikipedia
With the scanning objective, note the regular appearance of the intestinal mucosa with crypts and the lack of villi. Also note the abundance of goblet cells; these features are diagnostic. This is a good slide in which to review the structure of arteries, veins and the peripheral autonomic plexus. Note the cells with eosinophilic granules enteroendocrine cells in the lining epithelium. The rectum is histologically similar to the colon, and there is an abrupt transition between the rectal simple columnar epithelium and the stratified epithelium of the anal canal. The anal epithelium may appear stratified cuboidal at the junction with the rectum, but it assumes a typical stratified squamous appearance more distally.
The anal canal is the terminal segment of the large intestine between the rectum and anus , located below the level of the pelvic diaphragm. It is located within the anal triangle of perineum , between the right and left ischioanal fossa. As the final functional segment of the bowel, it functions to regulate release of excrement by two muscular sphincter complexes. The aperture at the terminal portion of the anal canal is known as the anus. In humans, the anal canal is approximately 2.
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.