Anal Channel

Anal canal Definition according to the doctor Shcheglov's dictionary The anal canal is a long, narrow, straight lacrimal passage at the end of the large intestine between the inner lining of the rectum and the muscles of its anterior wall. It is part of the anus. Its length is about 4-5 cm. With its outer end, the canal faces forward, with its inner end facing the posterior wall of the rectum. The external opening of the anal canal is covered with skin, its internal surface is covered with mucous membrane. In addition to skin and muscle tissue, it is covered with a layer of connective tissue for shock absorption and protection from shock and mechanical damage, as well as from tension in the abdominal wall muscles during defecation. Between the transverse septum of the anal canal and the wall of the rectum there is a special anal papilla that prevents the mucous membrane from everting into the intestinal lumen during exercise. In contact with the papilla, the sphincters tense, compressing the lumen and relaxing the urethral muscle, facilitating the release of urine from the bladder. The anal rectum is not a direct continuation of the intestine. In the lower part of the rectum there is a venous plexus, the duct of which is interconnected by bundles of striated muscles and forms the anal-rectal artery. It connects the veins of the rectum with the inferior vena cava system, while the veins of the anal part of the colon connect with the left common iliac vein through tributaries (superior epigastric vessels). Thus, the distribution of blood flow in the area of ​​the underlying anal region differs from the anastomoses of the small and large intestines. The importance of the pelvic venous plexus should be emphasized, because its expansion and metabolic disturbances occur under the influence of acute or chronic inflammatory processes in the pelvic peritoneum