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Anal Canal

DIVISIONS OF ANAL CANAL

Anal canal is unequally divided into two sections; Upper and Lower.

  1. Upper Division

2/3 of this canal is upper division and has longitudinal folds of Tunica Mucosa. Its lower ends are joined by folds of mucus membrane known as Anal Valves. This 2/3 upper region is supplied by Superior Rectal Artery, which is a branch of Inferior Mesenteric Artery.

  1. Lower Division

The remaining 1/3 of this canal is lower division and is lined by Stratified Squamous Epithelium which blends with skin. This region is supplied with Inferior Rectal Artery, which is a branch of the Internal Pudendal Artery.

EMBRYOLOGY

Anal canal develops from the Proctodeum below the dentate line while above the dentate line it develops from Hindgut’s endoderm.

NERVES

The anal canal skin doesn’t have skin appendages i.e. hairs and sweat glands, but has somatic nerve endings which are sensitive to pain.

MUSCLES

The anorectal ring is formed by innermost fibers of levator ani muscle extending from Pubic Bone, Obturator Fascia and Ischial Spine (Puborectalis).

ANAL CANAL CANCER

There are many cases of death from anal, anal canal, and anorectal cancer in USA. It is curable. The three major factors for it are Site,(anal canal vs. perianal skin) Size(primary tumors) and Nodal Status. The basic risk factor for this type of cancer is certain sexual practices like anal intercourse or a person with having a high lifetime number of partners. HPV (Human Papillomavirus) infections are also strongly related with anal cancer.

 


DIVISIONS OF ANAL CANAL

Anal canal is unequally divided into two sections; Upper and Lower.

  1. Upper Division

2/3 of this canal is upper division and has longitudinal folds of Tunica Mucosa. Its lower ends are joined by folds of mucus membrane known as Anal Valves. This 2/3 upper region is supplied by Superior Rectal Artery, which is a branch of Inferior Mesenteric Artery.

  1. Lower Division

The remaining 1/3 of this canal is lower division and is lined by Stratified Squamous Epithelium which blends with skin. This region is supplied with Inferior Rectal Artery, which is a branch of the Internal Pudendal Artery.

EMBRYOLOGY

Anal canal develops from the Proctodeum below the dentate line while above the dentate line it develops from Hindgut’s endoderm.

NERVES

The anal canal skin doesn’t have skin appendages i.e. hairs and sweat glands, but has somatic nerve endings which are sensitive to pain.

MUSCLES

The anorectal ring is formed by innermost fibers of levator ani muscle extending from Pubic Bone, Obturator Fascia and Ischial Spine (Puborectalis).

ANAL CANAL CANCER

There are many cases of death from anal, anal canal, and anorectal cancer in USA. It is curable. The three major factors for it are Site,(anal canal vs. perianal skin) Size(primary tumors) and Nodal Status. The basic risk factor for this type of cancer is certain sexual practices like anal intercourse or a person with having a high lifetime number of partners. HPV (Human Papillomavirus) infections are also strongly related with anal cancer.

 

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