The anal canal is the final segment of the digestive tract, about 4 cm long, running from the anorectal junction to the anal opening. It is surrounded by the internal and external anal sphincters and is normally held closed. Its upper part has vertical anal columns joined at their bases by anal valves, which form the pectinate line.
| Location | Perineum, from the anorectal junction at the level of the puborectalis sling to the anal verge, between the ischioanal fossae |
|---|---|
| Parts |
|
| Nerve Supply | Inferior hypogastric plexus (above the pectinate line); Inferior rectal (anal) nerves from the pudendal nerve, S2-S4 (below the pectinate line) |
| Blood Supply | Superior rectal artery (above the pectinate line); Middle rectal arteries; Inferior rectal arteries (below the pectinate line) |
| Venous drainage |
|
| Lymphatic drainage |
|
Maintains continence through its sphincters and vascular cushions and allows controlled passage of faeces and gas.
The pectinate line divides the canal into an upper part with visceral nerves, portal venous drainage and internal iliac lymphatics, and a lower part with somatic nerves (so very sensitive to pain), systemic venous drainage and superficial inguinal lymphatics. Anal glands open into the anal sinuses above the valves, and their infection causes most anal abscesses and fistulas. Fissures typically occur in the posterior midline.
Enlarged vascular cushions of the anal canal causing painless bright red bleeding (internal) or painful swelling when thrombosed (external).
Tear in the lining of the lower anal canal, usually in the posterior midline, causing severe pain on defecation and sphincter spasm.
Abnormal tract between an infected anal gland and the perianal skin, usually following an anal abscess.
This website uses cookies to enhance your experience. Some are essential for site functionality, while others help us analyze and improve your usage experience. Please review your options and make your choice.
If you are under 16 years old, please ensure that you have received consent from your parent or guardian for any non-essential cookies.
Your privacy is important to us. You can adjust your cookie settings at any time. For more information about how we use data, please read our privacy policy. You may change your preferences at any time by clicking on the settings button below.
Note that if you choose to disable some types of cookies, it may impact your experience of the site and the services we are able to offer.
Some required resources have been blocked, which can affect third-party services and may cause the site to not function properly.
This website uses cookies to enhance your browsing experience and ensure the site functions properly. By continuing to use this site, you acknowledge and accept our use of cookies.
