This structure begins from the rectum and extends to the skin.

Arteries:

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Superior rectal artery, which is a branch of the inferior mesenteric artery. It supplies the rectum and anus up to the anal valves. It is the main arterial supply to the rectum and anus and it anastomoses with other branches.

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Inferior rectal artery, which is a branch of the internal pudendal artery. This gives blood supply mainly to the anus distal to anal valves but anastomoses with the superior rectal branches across the valves.

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Middle rectal artery, which is a branch of the internal iliac artery. Its supply is minimal but supplies muscles of the lower part of rectum (e.g. internal anal sphincter and external anal sphincter). Its anastomoses is poor.

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Median sacral artery supplies posterior wall of anorectal junction. It is derived from the point of bifurcation of aorta. It forms appreciable anastomoses with other rectal veins, especially the inferior rectal vein.

Veins:

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Superior rectal vein, which is a tributary of the inferior mesenteric vein. It drains the rectum and anus up to the anal valves. It anastomoses with other branches.

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inferior rectal vein, which is a tributary of the internal pudendal vein. This gives blood supply, mainly to the anus from distal to anal valves but anastomoses with the superior rectal venous tributaries across the valves.

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Middle rectal vein which is a tributary of the internal iliac vein. It drains the muscles of the lower part of rectum (e.g. the internal and external anal sphincters). Its anastomoses is poor.

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Median sacral vein drains posterior wall of anorectal junction. It does not form any appreciable anastomoses.

Muscles

Anus at Layer 4 of female pelvis

Muscles of the anal canal occupy the position of muscularis in the large intestine. There are two sphincters and one subcutaneous muscle as follows

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External anal sphincter

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Internal anal sphincter

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Corrugator cutis ani

 

Layer 2 of male perineum.. Anus

The external anal sphincter is further divided into three parts

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Superficial external anal sphincter , which is the most superficial

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Subcutaneous xternal anal sphincter  

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Deep external anal sphincter . This is placed at the anorectal junction.

Nerves:

Autonomic fibers supply the upper 2/3 of anal canal -the visceral part -as follows

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Parasympathetic fibers are through the pelvic splanchnic nerves (or nervi erigentes) from S2-4.

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Sympathetic fibers are from the lumbar splanchnic nerves, which relay in the inferior mesenteric ganglion of the inferior mesenteric plexus and are from the inferior hypogastric plexus.

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Nerve of the anal-pit part of the anal canal are somatic and derived from the inferior rectal nerve

Nerve to the muscles are somatic and are as follows-

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Corrugator cutis ani by the perineal branch of S4

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Subcutaneous external sphincter is by inferior rectal nerve

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Superficial external sphincter by perineal branch of S4

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Deep external sphincter by the  inferior rectal nerve

More

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Electronic School of Medicine
Creator: Oluwole Ogunranti


Anus 


Intestine to anus- 3D model

 
DIGITAL LOCATOR OF FEMALE ANUS: Layer 1, layer of skin of female pelvis. Layer 2, layer of pelvic fascia. Layer 3 layer of greater pelvis, Layer 4, layer of lesser pelvis.  Rollover mouse to label, click to display page.; click blinking end page to display anus.

 
DIGITAL LOCATOR OF MALE ANUS:  Layer 1 Layer of skin of male perineum. Layer 2 Layer of superficial fascia of male perineum.  Roll over mouse to label and click to display. Click blinking end page to display anus page.

 

  


Hemorrhoid

 

1 rectum 2 levator ani 3 anal column 4 deep part of external anal sphincter 5 superficial part of external anal sphincter 6 peri-anal fascia 7 subcutaneous part of external anal sphincter 8 internal anal sphincter 9 (Hilton's) white line 10 anocutaneous junction 11 annulus hemorrhoidalis 12 pecten 13 anal sinus

 

 

1 anus, 2 rectum

 

  Layer 1 Layer of skin of male perineum

 

 

 

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