endaþarm

The endaþarm, or rectum, is the final section of the large intestine, connecting the sigmoid colon to the anal canal. In adults it is about 12 to 15 cm long. Its main role is to store feces and coordinate defecation, aided by the internal and external anal sphincters and the pelvic floor to maintain continence.

Anatomy: The rectum lies in the pelvis, begins at the level of the third sacral vertebra, and ends at the anorectal junction. It has an ampullated, relatively straight segment followed by the anal canal. The mucosa above the pectinate line is simple columnar; below it, the mucosa becomes non-keratinized stratified squamous.

Vascularization: Arterial supply comes from the superior rectal artery (a branch of the inferior mesenteric) and from the middle and inferior rectal arteries (branches of the internal iliac). Venous drainage mirrors this, with the upper rectal veins draining to the portal system via the inferior mesenteric vein, and the middle and inferior rectal veins draining to the systemic circulation via the internal iliac veins.

Lymph and nerves: Lymphatics drain to inferior mesenteric nodes above the pectinate line and to internal iliac nodes below. Innervation includes parasympathetic fibers from the pelvic splanchnic nerves and sympathetic fibers via the hypogastric plexus; somatic control of the external sphincter is via the pudendal nerve.

Physiology and clinical topics: The rectum acts as a reservoir and participates in the defecation reflex. Conditions include hemorrhoids, rectal prolapse, and rectal cancer. Screening (sigmoidoscopy or colonoscopy) and treatment depend on location and pathology.