Rectum The rectum belongs to the last section of the large intestine (colon). Together with the anal canal (Canalis analis), the rectum is used for stool excretion (defecation).
Structure
The rectum is about 12 – 18 cm long, although this can vary from person to person. The name rectum is somewhat misleading for the rectum, because the rectum is not straight, but has curves in two planes. In the lateral view, the rectum has two curves, the so-called flexura sacralis and the flexura perinealis.
The flexura sacralis points more in the direction of the sacrum, while the flexura perinealis curves more in the direction of the abdominal cavity, i.e. the front wall. When viewed from the front, one can also see bends in the rectum which are deviated to the side. These bends are called flexurae laterales.
There are three flexurae laterales. Opposite each bend is a corresponding fold in the mucosa of the rectum (plicae transversae recti). Of these three mucosal folds, the middle fold is particularly significant.
This middle mucosal fold is also called the Kohlrausch fold. The kohlrausch-fold is the most pronounced of the three folds and protrudes 6-7 cm into the intestinal lumen. The kohlrausch-fold marks the end of the ampulla recti.
The ampulla recti extends below the kohlrausch-fold and is the lowest section of the rectum. It is clinically important that a digital rectal examination (a palpation in which the doctor palpates the rectum with his finger) can be palpated approximately up to the Kohlrausch fold. Thus, hardenings such as tumors can be manually diagnosed here.
Below the ampulla recti, the junctio anorectalis limits the transition from rectum to anal canal. The anal canal is still about 3 – 4 cm long and represents the very last part of the gastrointestinal tract. The end of the anal canal opens outwards as an anus between the two buttocks.
The wall structure of the rectum has three layers. The outermost layer is formed by the peritoneum and fasciae. The middle layer is the muscle layer.
This consists of longitudinal muscles and ring muscles. The ring musculature is strengthened especially in the area of the anal canal as the muscle sphincter ani internus (inner sphincter muscle). The innermost layer in the wall structure is the mucosa. It lines the inside of the rectum.
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