rectoanalis

Rectoanalis is a Latin anatomical term historically used to refer to the region where the rectum meets the anus, or more broadly to the relations of the rectum and anal canal. In modern anatomical language, the area is described as the anorectal region, and the preferred terms are rectoanal or anorectal.

Anatomy: The rectoanal region comprises the distal rectum, the anal canal, and the surrounding pelvic floor tissues. The junction is at the pectinate line, marking a transition from columnar to non-keratinized stratified squamous epithelium. The internal anal sphincter, a thickened ring of smooth muscle, maintains resting tone, while the external anal sphincter, composed of skeletal muscle, provides voluntary control. The puborectalis muscle contributes to the anorectal angle, aiding continence. Blood supply comes from the superior rectal artery (branch of the inferior mesenteric) and the middle and inferior rectal arteries (from the internal iliac). Venous drainage mirrors this pattern. Lymph drainage generally follows vascular patterns to internal iliac and superficial inguinal nodes. Innervation includes autonomic fibers to the internal sphincter and somatic pudendal nerves to the external sphincter.

Function: The region plays a central role in continence and defecation. The internal sphincter provides involuntary tone; the external sphincter and pelvic floor provide voluntary control; relaxation during defecation reduces anal resistance; the anorectal angle straightens during passage of stool.

Clinical considerations: Diseases of the rectoanal region include hemorrhoidal disease, anal fissures, abscesses, and cancers that involve the rectum or anal canal. Evaluation may use anoscopy or endoscopy. Injury to the sphincters or pelvic floor, including obstetric trauma, can impair continence and may require surgical repair.