Jump to content

Anal canal: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Apparently the original text was wrong and it should be cm
c/e
Line 16: Line 16:
| Lymph = [[Superficial inguinal lymph node]] (below pectinate line) and [[internal iliac lymph nodes]] (above line)
| Lymph = [[Superficial inguinal lymph node]] (below pectinate line) and [[internal iliac lymph nodes]] (above line)
}}
}}
The '''anal canal''' is the terminal segment of the [[large intestine]] between the [[rectum]] and [[anus]], located below the level of the [[pelvic diaphragm]]. It is located within the [[anal triangle]] of [[perineum]], between the right and left [[ischioanal fossa]]. As the final functional segment of the bowel, it functions to regulate release of excrement by two muscular sphincter complexes. The aperture at the terminal portion of the anal canal is known as the anus.
The '''anal canal''' is the terminal segment of the [[large intestine]], between the [[rectum]] and [[anus]], located below the level of the [[pelvic diaphragm]]. It is located within the [[anal triangle]] of the [[perineum]], between the right and left [[ischioanal fossa]]. As the final functional segment of the [[bowel]], it functions to regulate release of [[excrement]] by two muscular [[sphincter]] complexes. The anus is the aperture at the terminal portion of the anal canal.


==Structure==
==Structure==
Line 27: Line 27:
* upper zone (zona columnaris)
* upper zone (zona columnaris)
** mucosa is lined by [[simple columnar epithelium]]
** mucosa is lined by [[simple columnar epithelium]]
** features longitudinal folds or elevations of tunica mucosa which are joined together inferiorly by folds of [[mucous membrane]] known as anal valves
** features longitudinal folds or elevations of tunica mucosa which are joined together inferiorly by folds of [[mucous membrane]] known as [[anal valves]]
** supplied by the [[superior rectal artery]] (a branch of the [[inferior mesenteric artery]])
** supplied by the [[superior rectal artery]] (a branch of the [[inferior mesenteric artery]])
* lower zone
* lower zone
** divided into two smaller zones, separated by a white line known [[Intersphincteric groove|Hilton's line]]:
** divided into two smaller zones, separated by a white line known [[Intersphincteric groove|Hilton's line]]:
*** zona hemorrhagica - lined by [[stratified squamous epithelium|stratified squamous non-keratinized]] epithelium
*** zona hemorrhagica - lined by [[stratified squamous epithelium|stratified squamous non-keratinized epithelium]]
*** zona cutanea - lined [[stratified squamous epithelium|stratified squamous keratinized]] epithelium, which blends with the surrounding perianal skin
*** zona cutanea - lined [[stratified squamous epithelium|stratified squamous keratinized epithelium]], which blends with the surrounding perianal skin
** supplied by the [[inferior rectal artery]] (a branch of the [[internal pudendal artery]])
** supplied by the [[inferior rectal artery]] (a branch of the [[internal pudendal artery]])


The ''anal verge'' refers to the [[Anatomical terms of location#Proximal and distal|distal]] end of the anal canal, a transitional zone between the epithelium of the anal canal and the [[perianal skin]]. It should not be confused with the [[pectinate line]] between the upper and lower zones within the anal canal.
The ''anal verge'' refers to the [[Anatomical terms of location#Proximal and distal|distal]] end of the anal canal, a transitional zone between the [[epithelium]] of the anal canal and the [[perianal skin]]. It should not be confused with the pectinate line between the upper and lower zones within the anal canal.


[[Anal gland]] secretes lymphal discharge and built up fecal matter from the colon lining. In some animals this gland expungement can be done routinely every 24 – 36 months to prevent infection and fistula formation.
[[Anal gland]] secretes lymphal discharge and built-up [[feces|fecal matter]] from the [[colon]] lining. In some animals this gland expungement can be done routinely every 24–36 months to prevent infection and [[fistula]] formation.


===Relations===
===Relations===
Line 45: Line 45:


==Function==
==Function==
The external anal sphincter muscle is the voluntary muscle that surrounds and adheres to the anus at the lower margin of the anal canal. This muscle is in a state of tonic contraction, but during defecation, it relaxes to allow the release of feces.
The [[external anal sphincter]] muscle is the voluntary muscle that surrounds and adheres to the anus at the lower margin of the anal canal. This muscle is in a state of [[tetanic contraction|tonic contraction]], but during [[defecation]], it relaxes to allow the release of [[feces]].


Movement of the feces is also controlled by the involuntarily controlled internal anal sphincter which is an extension of the circular muscle surrounding the anal canal. It relaxes to expel feces from the rectum and anal canal.
Movement of the feces is also controlled by the involuntarily controlled internal anal sphincter, which is an extension of the circular muscle surrounding the anal canal. It relaxes to expel feces from the rectum and anal canal.


==Additional images==
==Additional images==
<gallery>
<gallery>
Image:Anorectum-en.svg |Anatomy of the anus and rectum
Image:Anorectum-en.svg |Anatomy of the anus and rectum
Image:Gray404.png|Left levator ani from within.
Image:Gray404.png|Left levator ani from within
Image:Gray1080.png|The interior of the anal canal and lower part of the rectum.
Image:Gray1080.png|The interior of the anal canal and lower part of the rectum
Image:Gray1228.png|Median sagittal section of male pelvis.
Image:Gray1228.png|Median sagittal section of male pelvis
Image:Gray1230.png|Median sagittal section of female pelvis.
Image:Gray1230.png|Median sagittal section of female pelvis
</gallery>
</gallery>


Line 62: Line 62:
* [[Anal columns]]
* [[Anal columns]]
* [[Anal sinuses]]
* [[Anal sinuses]]
* [[Anal valves]]
* [[Anus]]
* [[Pectinate line]]
* [[Anal sex]]
* [[Anal sex]]


Revision as of 02:46, 17 October 2020

Anal canal
Anatomy of the anus and rectum
Coronal section through the anal canal. B. Cavity of urinary bladder V.D. Ductus deferens. S.V. Seminal vesicle. R. Second part of rectum. A.C. Anal canal. L.A. Levator ani. I.S. Sphincter ani internus. E.S. Sphincter ani externus.
Details
PrecursorHindgut, proctodeum
Arterysuperior rectal artery (above pectinate line) and inferior rectal artery (below line)
Veinsuperior rectal vein (above pectinate line) and inferior rectal vein (below line)
Nerveautonomic inferior hypogastric plexus (above pectinate line) and somatic inferior rectal nerves (below line)
LymphSuperficial inguinal lymph node (below pectinate line) and internal iliac lymph nodes (above line)
Identifiers
LatinCanalis analis
MeSHD001003
TA98A05.7.05.001
TA23009
FMA15703
Anatomical terminology

The anal canal is the terminal segment of the large intestine, between the rectum and anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional segment of the bowel, it functions to regulate release of excrement by two muscular sphincter complexes. The anus is the aperture at the terminal portion of the anal canal.

Structure

In humans, the anal canal is approximately 2.5 to 4 cm long, from the anorectal junction to the anus.[1][2][3] 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 slit.

The canal is differentiated from the rectum by a transition along the internal surface from endodermal to skin-like ectodermal tissue.

Anal canal is traditionally divided into two segments, upper and lower, separated by the pectinate line (also known as the dentate line):

The anal verge refers to the distal end of the anal canal, a transitional zone between the epithelium of the anal canal and the perianal skin. It should not be confused with the pectinate line between the upper and lower zones within the anal canal.

Anal gland secretes lymphal discharge and built-up fecal matter from the colon lining. In some animals this gland expungement can be done routinely every 24–36 months to prevent infection and fistula formation.

Relations

Function

The external anal sphincter muscle is the voluntary muscle that surrounds and adheres to the anus at the lower margin of the anal canal. This muscle is in a state of tonic contraction, but during defecation, it relaxes to allow the release of feces.

Movement of the feces is also controlled by the involuntarily controlled internal anal sphincter, which is an extension of the circular muscle surrounding the anal canal. It relaxes to expel feces from the rectum and anal canal.

Additional images

  • Anatomy of the anus and rectum
    Anatomy of the anus and rectum
  • Left levator ani from within
    Left levator ani from within
  • The interior of the anal canal and lower part of the rectum
    The interior of the anal canal and lower part of the rectum
  • Median sagittal section of male pelvis
    Median sagittal section of male pelvis
  • Median sagittal section of female pelvis
    Median sagittal section of female pelvis

See also

This article uses anatomical terminology.

References

  1. ^ "Anal canal".{{cite web}}: CS1 maint: url-status (link)
  2. ^ Anal+Canal at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  3. ^ https://www.knowyourbody.net/anal-canal.html
  • pelvis at The Anatomy Lesson by Wesley Norman (Georgetown University)
  • Anatomy figure: 44:05-00 at Human Anatomy Online, SUNY Downstate Medical Center — "The rectum and anal canal in the male pelvis"
Retrieved from "https://en.wikipedia.org/w/index.php?title=Anal_canal&oldid=983926367"