Rectum
It stretches from the limit of the sigmoid colon to the pectinate line (limit between the rectal mucosa and the skin of the anus), with a length that goes from 12 to 15 centimeters. It is catalogued as the place where the solid waste is retained prior to defecation (elimination).
Because of this, it is usually empty, except before and during the evacuation of feces. It follows the curve of the sacrum and coccyx (stretching from the second sacral vertebra to the vertex of the coccyx). It has a mucous lining (of shiny appearance) that contains mucus glands similar to those located along the intestinal tract, which ease the advancement of waste towards the anal orifice.
Anus
With a length close to four centimeters, it is the final part of the digestive tube. It communicates with the rectum on its superior side and with the skin that surrounds the anal orifice on its inferior side, reason for which it is covered by mucosa and skin.It has three important muscles: the external sphincter, the internal one and the levator muscle of the anus. The first of them consists of striated muscle fibers and acts voluntarily, enabling us to hold off the need to defecate (it does so through successive contractions).
The internal anal sphincter resembles a flat sheet of muscles and responds to a series of unconscious stimuli that are unleashed when its time to evacuate the feces. Finally, the levator muscle of the anus allows retention and fractioning of the feces, also preventing them from coming out due to gravity.
Muere Evita