Anatomy of Anal Anal

7/31/2019 Anatomy of Anal Anal

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Maham Ashraf

Roll no 66


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Anal canal commences at the level where rectum passesthrough pelvic diaphragm and ends at anal verge

The muscular junction between rectum and anal canal canbe felt wiTh the finger as thickened ridge anorectal ring


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anal canal

contains

Internalsphincter

Longitudinalmuscle

Externalsphincter


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It is the continuation of circular muscle coatof rectum

It commences where rectum passes throughpelvic diaphragm and ends at anal orifice

It is involuntary in nature


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It is formed by the fusion of puborectalis with thelongitudinal muscle coat of rectum at anorectal junction

It lies between external and internal sphincter

Its fiber fan out through the lowest part of externalsphincter to be inserted into and perianal skin


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It is subdivided into deep, superficial and subcutaneouspart

SUBCUTANEOUSpart lies below the level of internalanal sphincter and surround the lowest part of anal canal

SUPERFICIAL partarise from posterior surface ofterminal segment of coccyx and are inserted in perinealbody


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DEEP PARTsurround the upper part of internal analsphincter and is fused with puborectalis

It has no bony attachment


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It marks the junction between rectum and anal canal

It is formed by joining of puborectalis,deep externalsphincter, conjoint longitudinal muscle and highest fiberof internal anal sphincter

It can be felt digitally

Division of anorectal ring result in permanentincontinence


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It is divided into

Upper mucous part

Middle part or transition zone or pecten

Lower cutaneous part


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This part is 15mm long.It is endodermal in origin

The mucous membrane show

a) 6 to 12 vertical folds called anal column of morgagni

b) the lower end of anal column are united to each otherby transverse fold of mucous membrane called analvalve


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Above each valve there is a depression in mucosa called

anal sinus

Anal valve together form a transverse line that run allaround the anal canal called DENTATE LINE ORPECTINATE LINE


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The next 15mm of anal canal is also lined by mucousmembrane but anal column are not present

The mucosa has a bluish appearance because of densevenous plexus and is less mobile

The lower limit has a whitish appearance and is calledwhite line of Hilton


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It is about 8mm long and is lined by true skin containingsweat and sebaceous glands


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ABOVE

Cuboidal epithelium

Autonomic nervous

system [insensitive] Venous drainage is by

portal system

Lymphatic drainage is by

Para aortic nodes

BELOW

Squamous epithelium

Somatic nerve [sensitive]

Venous drainage is bysystemic vein

By superficial and deep

inguinal nodes


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The part of anal canal above dentate line is supplied by

superior rectal artery

The part below dentate line is supplied by inferior rectalartery


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INTERNAL RECTAL VENOUS PLEXES lies in the submucosa of anal canal it drain mainly into superior rectalvein but communicate freely with middle and inferiorrectal vein

EXTERNAL RECTAL VENOUS PLEXES lies outsidemuscular coat of anal canal and communicate freely withinternal rectal plexus


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The lower part of external plexus is drained by inferiorrectal vein into internal pudendal vein

The middle and superior part is drained by middle andsuperior rectal veins respectively both of which drain intoportal vein via inferior mesenteric vein


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ABOVE DENTATE LINE anal canal is supplied byautonomic nervous system

BELOW DENTATE LINE it is supplied by somatic [inferiorrectal S2,S3,S4]

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Anatomy of Anal Anal