Anal canal
Anal Canal
The Anal Canal (pronunciation: /ˈeɪnəl kəˈnæl/) is the terminal part of the large intestine. It is situated between the rectum and anus, below the level of the pelvic diaphragm. It lies in the anal triangle of perineum in between the right and left ischioanal fossa.
Etymology
The term "Anal Canal" is derived from the Latin words "anus" meaning ring or circle, and "canalis" meaning tube or pipe.
Anatomy
The anal canal is approximately 3 to 4 cm long, extending from the anorectal junction to the anus. It is directed downwards and backwards. It is surrounded by inner involuntary and outer voluntary sphincter muscles, the internal anal sphincter and the external anal sphincter respectively, which control the expulsion of feces.
Histology
The upper half of the anal canal is lined by rectal columnar epithelium, while the lower half is lined by stratified squamous epithelium. The point of transition is a serrated line, known as the pectinate line.
Function
The anal canal functions as a pathway for the removal of fecal matter from the body. The internal and external sphincters control the passage of feces.
Related Terms
- Anus: The external opening of the anal canal.
- Rectum: The final straight portion of the large intestine, connecting the sigmoid colon to the anal canal.
- Sphincter: A circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning.
- Pectinate Line: The line which divides the upper two-thirds and lower one-third of the anal canal.
External links
- Medical encyclopedia article on Anal canal
- Wikipedia's article - Anal canal
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