Anatomy of the Rectum and Anal Canal

Lymph vessels from the lower rectum excrete the sacral lymph nodes and then enter the orbital lymph nodes. The sympathetic nerve of the rectum dominates the periportal plexus through the lower abdominal plexus and the superior rectal artery from the lumbar spinal cord area. Parasympathetic and visceral afferent fibers for the rectum include the internal iliac spinal cord segment and the ganglion 1. The anal canal is the terminal part of the colon 1. It extends from the top of the pelvic diaphragm to the anus 1.

When the rectum is full, as the pressure in the rectum rises, the anal canal wall separates, allowing feces to enter the duct. When a substance is pushed into the anal canal, the rectum becomes shorter and peristaltic waves push the feces out of the rectum. The internal anal sphincter and the external anal sphincter, together with the puborectal muscle, allow the feces to withdraw the anus from the excreted feces through the muscle. Defecation is usually aided by expelling this air from deep breaths and closed glottis (Valsalva action). This contraction of expiratory chest muscles, diaphragm muscles, abdominal wall muscles and diaphragm muscles of the pelvis pressure the digestive tract. Ventilation at this time temporarily stops because the lung pushes down the chest diaphragm and exerts pressure. Rise in blood pressure and reflex response in the chest

The anus is the opening at the end of the anal canal. The rectum is located between the colon and the anus and serves as a faeces holding chamber. When the rectal pressure becomes too much, the inner muscle ring called the anal sphincter relaxes, allowing feces to pass through the anal canal, the anus and the body. The anus consists of glands, ducts, vessels, mucus, tissues and nerve endings, which are very sensitive to pain, irritation and other sensations. According to cause, anal swelling is felt warm, severe or burning sensation (especially after bowel movement), bleeding and pus