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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]