The Rectum. Introduction

investinum). It means straight intestine.
- is the final straight portion of the large intestine.
- the human Rectum is about 12 cm long and begins rectosigmoid junction.

has an important role as a temporary store of feces.
- it is continuous proximally with the sigmoid colon and terminates into the anal.

by the tone of the puborectalis muscle, and contributes significantly to faecal continence.

Rectum

Sacral flexure – anteroposteriorcurve with concavity anteriorly (follows the curve of the sacrum and coccyx).

formed by transverse folds of the internal rectum wall.
The final segment of the rectum, the ampulla, relaxes to accumulate and temporarily store faeces until defecation occurs. It is continuous with the anal canal; which passes through the pelvic floor to end as the anus.

As the rectal walls expand due to the materials filling it from within, stretch receptors from the nervous system located in the rectal walls stimulate the desire to defecate. If the urge is not acted upon, the material in the rectum is often returned to the colon where more water is absorbed from the feces. If defecation is delayed for a prolonged period, constipation and hardened feces results.
When the rectum becomes full, the increase in intrarectal pressure forces the walls of the anal canal apart, allowing the fecal matter to enter the canal. The rectum shortens as material is forced into the anal canal and peristaltic waves propel the feces out of the rectum. The internal and external sphincter allow the feces to be passed by muscles pulling the anus up over the exiting feces

The rectum is a continuation of the sigmoid colon, and connects to the anus. The rectum follows the shape of the sacrum and ends in an expanded section called the rectal ampulla, where feces are stored before their release via the anal canal. An ampulla is a cavity, or the dilated end of a duct, shaped like a Roman ampulla.
Unlike other portions of the colon, the rectum does not have taeniae coli.
The rectum connects with the sigmoid colon at the level of S3, and connects with the anal canal as it passes through the pelvic floor muscles.Supports of the rectum include:
• Pelvic floor formed by levator and muscles.
• Waldeyer's fascia
• Lateral ligaments of rectum which are formed by the condensation of pelvic fascia
• Rectovesical fascia of Denonvillers, which extends from rectum behind to the seminal vesicles and prostate in front.
• Pelvic peritoneum
• Perineal body