Rektums

The rectum is the final section of the large intestine, extending from the end of the sigmoid colon to the anal canal. It serves primarily as a temporary storage site for feces before defecation. Positioned in the pelvis, the rectum delivers stool to the anal canal and coordinates the defecation reflex through neural and muscular mechanisms.

Anatomy and structure include several distinctive features. The rectal mucosa is lined by simple columnar epithelium in most of its length, transitioning to non-keratinized stratified squamous epithelium in the anal canal. It contains three transverse folds known as the valves of Houston, which help sustain fecal continuity. The rectal ampulla is a dilation just above the anal canal that accommodates fecal matter. The taeniae coli converge as they approach the rectum, contributing to the organ’s muscular configuration. The rectum is supplied by the superior rectal artery (from the inferior mesenteric artery) and by the middle and inferior rectal arteries (branches of the internal iliac arteries). Venous drainage follows similar pathways to the portal and systemic circulations. Innervation involves the autonomic nervous system: parasympathetic input from pelvic splanchnic nerves and sympathetic input from the hypogastric plexus, with sensory fibers conveying distension signals to regulate defecation.

Functionally, the rectum acts as a reservoir and participates in defecation. The internal anal sphincter (involuntary) relaxes in response to stretch, while the external anal sphincter (voluntary) provides conscious control. Clinically relevant conditions include hemorrhoids, rectal prolapse, rectal cancer, and disorders of continence or evacuation. Screening and examinations, such as digital rectal exams and endoscopic assessments, aid in diagnosis.