Organ
Anal canal
The continence-controlled outlet of the gut
High-yield
The pectinate line organizes regional distinctions, but epithelial transitions and vascular or lymphatic territories overlap instead of switching uniformly at one line.
Overview
The anal canal links rectum to body surface. Internal smooth muscle, external skeletal muscle and puborectalis work with vascular cushions and sensation to maintain continence. Anatomical and surgical definitions account for differing quoted lengths.
Reference facts
- Location
- Extends from the anorectal junction to the anal verge in the perineum, flanked by ischioanal fat.
- Parts
- Proximal columns and sinuses end at valves forming the pectinate line. Distally the lining becomes squamous and then perianal skin. The surgical canal includes the anorectal ring and is often about 4 cm long.
- Blood supply
- Superior rectal branches predominate proximally and inferior rectal branches distally; middle rectal contributions and anastomoses vary.
- Innervation
- Proximal sensation is predominantly visceral. Inferior rectal somatic nerves provide distal sharp-pain, temperature and touch sensitivity; the proximal region is not wholly insensate.
- Venous/Lymphatic drainage
- Proximal venous return favors the portal route, with systemic connections. Proximal lymph uses mesorectal/inferior mesenteric and internal iliac routes; distal lymph commonly reaches superficial inguinal nodes.
- Relations
- Perineal body anteriorly, anococcygeal tissues posteriorly and ischioanal fossae laterally; sphincters surround the canal.
- Function
- Maintains closure between bowel movements and permits coordinated evacuation.
Clinical correlation
Obstruction and infection of anal glands can initiate an abscess and later a fistula. Their relation to the internal sphincter and intersphincteric tissues explains common routes of spread.
Frequently asked questions
Where is the anal canal located?
The anal canal lies extends from the anorectal junction to the anal verge in the perineum, flanked by ischioanal fat.
What does the anal canal do?
Maintains closure between bowel movements and permits coordinated evacuation.
What are the parts of the anal canal?
Proximal columns and sinuses end at valves forming the pectinate line. Distally the lining becomes squamous and then perianal skin. The surgical canal includes the anorectal ring and is often about 4 cm long.
What is the blood supply of the anal canal?
Superior rectal branches predominate proximally and inferior rectal branches distally; middle rectal contributions and anastomoses vary.