Search results
Results from the WOW.Com Content Network
Colorectal surgeons instead define the anal canal as the zone from the anal verge to the anorectal ring (palpable structure formed by the external anal sphincter and the puborectalis muscle). [1] Several distinctions can be made based upon the location of a structure relative to the pectinate line:
The internal anal sphincter, IAS, or sphincter ani internus is a ring of smooth muscle that surrounds about 2.5–4.0 cm of the anal canal.It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular muscle fibers of the rectum.
In humans, the anus (pl.: anuses or ani; from Latin ānus, "ring", "circle") [1] [2] is the external opening of the rectum located inside the intergluteal cleft. Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus.
In humans, the anal canal is approximately 2.5 to 4 cm (0.98 to 1.57 in) long, from the anorectal junction to the anus. [2] [3] [4] It is directed downwards and backwards.. It is surrounded by inner involuntary and outer voluntary sphincters which keep the lumen closed in the form of an anteroposterior sl
Stylized diagram showing action of the puborectalis sling, and the formation of the anorectal angle. A-puborectalis, B-rectum, C-level of anorectal ring and anorectal angle, D-anal canal, E-anal verge, F-representation of internal and external anal sphincters, G-coccyx & sacrum, H-pubic symphysis, I-Ischium, J-pubic bone.
It terminates at the level of the anorectal ring (the level of the puborectalis sling) or the dentate line, again depending upon which definition is used. [3] In humans, the rectum is followed by the anal canal, which is about 4 centimetres (1.6 in) long, before the gastrointestinal tract terminates at the anal verge.
This pulls the bowel forwards and forms the anorectal angle, the angle between the anal canal and the rectum. A-puborectalis, B-rectum, C-level of the anorectal ring and anorectal angle, D-anal canal, E-anal verge, F-representation of internal and external anal sphincters, G-coccyx & sacrum, H-pubic symphysis, I-Ischium, J-pubic bone.
Between the termination of the vertebral column and the anus, the two pubococcygeus muscles come together and form a thick, fibromuscular layer lying on the raphe (ridge) or (anococcygeal body) formed by the iliococcygei. The greater part of this muscle is inserted into the coccyx and into the last one or two pieces of the sacrum.