Anal Canal

The anal canal is the final 4-5 cm of the colon, surrounded by muscles at the end of the digestive system, between the rectum and the anal verge (anal orifice).

The perianal skin, including hair, sweat glands, and sebaceous glands, has keratinized and pigmented skin appendages. The skin of the anal canal above the anal verge, also known as the anoderm, is pigmented and keratinized and is sensitive to pain but does not have skin appendages.

The surgical anal canal is defined as the border between the anal canal and the rectum, known as the anorectal ring (anorectal angle). The anorectal ring is approximately 4-5 cm long and is formed by the puborectal muscle, which encircles the anorectal junction from behind and angles it forward. The dentate line divides the surgical anal canal into upper (hindgut) and lower (proctodeum) parts.

The anatomical anal canal is defined as having the upper border at the linea dentata (linea pectinea), which is approximately 2.5-3 cm long.

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