anus

Definition: The anal canal extends from the anorectal junction to the anal margin.

The dentate line marks the junction between squamous and mucosal epithelium in the anal canal. Immediately above the dentate line there is a zone of transitional epithelium. Below the dentate line, the canal is lined by non-keratinising squamous epithelium, which merges with the perianal skin.

The anal margin is the pigmented skin immediately surrounding the anal orifice.

The lymphatic drainage varies in different parts of the canal. Proximally drainage is to perirectal nodes along the inferior mesenteric artery. Lymph from immediately above the dentate line drains to internal pudendal nodes, and to the internal iliac system. Infra-dentate and perianal skin drains to the inguinal, femoral and external iliac nodes.

Pathology : anal pathology

 anal malformations
 anal anomalies
 anal lesional syndromes
 anal diseases
 anal tumors

See also

 digestive system

• digestive tube