Anatomy - Resection rectopexy, laparoscopic

Functionally, the rectum represents a fecal reservoir that prevents continuous fecal discharge. It connects directly to the sigmoid colon and, similar to it, exhibits an S-shaped a/p and lateral curvature (flexura sacralis, anorectalis, and lateralis). Typically, the rectum is divided into three sections:

1. Ampulla recti (main reservoir, ventral to the sacrum)
2. Anal canal (see below, closure region between the anorectal flexure and the skin opening)
3. Between 1 and 2, an unspecified section that emerges at a right angle from 1 and similarly transitions at a right angle into 2. Here, typical folds are found in the mucosa (Kohlrausch folds).

Adjacent structures of the rectum are dorsally the sacrum and coccyx, laterally next to the internal iliac A. and V. the regional lymph nodes, the sacral plexus and parts of the autonomic nervous system as well as ureters and adnexa. Ventrally, in the female organism, uterus and vagina, in the male the urinary bladder and prostate/seminal vesicles. Caudally is the pelvic floor.

Three muscles form the closure apparatus in the wall of the lower rectum:

1. The M. sphincter ani internus represents a thickening of the last circularly running fibers of the smooth colon musculature and is innervated by the sympathetic nervous system.
2. The M. levator ani is, on the other hand, voluntarily innervated (sacral plexus) and the M. puborectalis attached to the pubic bone is also attributed to it. It pulls as a large loop around the anal canal ventrally and thereby functionally kinks it.
3. The M. sphincter ani externus is also striated and suspended between the center of the perineal region (Centrum perinei) and the coccyx. It is voluntarily innervated by the pudendal nerve. Through its contraction, the anal canal is terminally closed.

The different innervation of the three closing muscles provides additional security against failures and resulting incontinence.
In the mucosa of the anal canal, there are numerous longitudinally running folds (Columnae anales), which exhibit dense arterial (!) plexuses with venous drainage. Upon contraction of the sphincter muscles, they fill up quickly and the mucosa swells, lies against each other, and thus provides a gas-tight closure. Hemorrhoids and venous thromboses are well-known vascular-related complications of this region.

Defecation occurs on the one hand through the relaxation of the closure mechanisms (initiated by the voluntary musculature, emptying of the vascular cushions) and on the other hand through active abdominal press and the peristalsis of the intestine.