What is the rectum and what is its function?

The rectum is the terminal part of the large intestine, located between the sigmoid colon and the anal canal. Its primary function is to store feces, with distension initiating the desire to defecate. Unlike other parts of the large intestine, it lacks features like taenia coli and haustra.

How long is the rectum and what is its anatomical course?

The rectum is approximately 12 cm (5 inches) long. Its course involves three parts: the upper third goes downward and backward, the middle third goes vertically downward, and the lower third goes downward and forward to the anorectal junction. It forms a dilated ampulla in the lower part.

What are the key anatomical relations of the rectum?

The rectum has important relations that differ by sex and location. Anteriorly, in males, it relates to structures like the bladder and prostate; in females, it relates to the vagina. Posteriorly, it is adjacent to the sacrum and coccyx in both sexes. Laterally, it is near the levator ani muscle and pelvic fascia.

What are the blood supply and venous drainage of the rectum?

The rectum receives arterial blood from the superior rectal, middle rectal, inferior rectal, and median sacral arteries. Venous drainage involves the superior rectal vein to the portal system and the middle and inferior rectal veins to the systemic system, creating a portocaval anastomosis at the mid-rectal region.

What are Houston's valves and why are they important?

Houston's valves are 3–4 permanent transverse folds inside the rectum, including a large and constant third fold on the anterior wall. They help prevent overdistension and aid in stool retention. Clinically, the third valve can impede medical instrumentation, so procedures often use a left lateral position.

What are the clinical implications of rectal prolapse?

Rectal prolapse involves protrusion of rectal tissue and can be incomplete (mucosal prolapse due to weak submucosa) or complete (full-thickness eversion from weak pelvic support). Symptoms include protrusion, mucous discharge, bleeding, pain, and incontinence.

How is the rectum supported anatomically?

The rectum is supported by several structures, including the pelvic diaphragm (levator ani and puborectalis sling), the fascia of Waldeyer binding it to the sacrum and coccyx, and lateral ligaments containing middle rectal vessels. These help maintain its position and function.

Rectum – Curvatures, Houston Valves & Support

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