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Uploaded bySneha Chaudhary
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Anal canal: features and relation

The document summarizes the anatomy of the anal canal. It begins by introducing the anal canal and its location in the gastrointestinal tract. It then describes the features, extent, course, relations, interior regions divided by the pectinate and Hilton's lines, and musculature including the internal and external anal sphincters. In summary, the document provides an overview of the key anatomical structures and regions of the anal canal.

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ANAL CANAL SNEHA CHAUDHARY ROLL NO. – 159 BATCH - 2019
LEARNING OBJECTIVES  INTRODUCTION  FEATURES  EXTENT AND COURSE  RELATIONS  INTERIOR OF ANAL CANAL  MUSCULATURE OF ANAL CANAL  MCQS
INTRODUCTION  Terminal part of gastrointestinal tract.  Situated below the level of pelvic diaphragm.  Surrounded by an inner involuntary sphincter and an outer voluntary sphincter.  keep the anal canal closed except during the defecation.
FEATURES  The anal canal is 3.8cm or 38mm long.  Like rectum it is devoid of sacculation, taenia coli. LOCATION  Lies in the anal triangle of perineum in between the left and right ischioanal fossae
EXTENT AND COURSE  Extend from the anorectal junction to the anus.  Directed downwards and backwards.  Anorectal junction is marked by forward convexity of the perineal flexure of the rectum.  Lies 2-3cm in front of and slightly below the tip of coccyx.  Anus is the surface opening of anal canal, lies 4cm below and in front of tip of coccyx.
RELATIONS  ANTERIORLY 1. In both: Perineal body. 2. In males: Membranous urethra and bulb of penis. 3. In females: Lower end of the vagina.  POSTERIORLY 1. Anococcygeal ligament. 2. Tip of the coccyx.
 LATERALLY  Ischioanal fossae.  ALL-ROUND  Surrounded by sphincter muscles.
INTERIOR OF ANAL CANAL  Divided into 3 areas by Pectinate and Hilton's line. 1. Upper mucous area (15mm) 2. Intermediate area /Pecten (15mm) 3. Lower cutaneous area (8mm)
PECTINATE LINE  Anal valves together form a transverse line that runs all-round the anal canal. WHITE LINE OF HILTON’S  The lower limit of the pecten often has a whitish appearance.  Situated at the interval between the upper part of external anal sphincter and the lower end of internal anal sphincter.
FEATURES OF UPPER PART
FEATURES OF MIDDLE PART  This regions is referred as pecten or transitional zone.  Lined by mucous membrane  Ectodermal in origin.  Anal columns are absent.  Mucosa has a bluish appearance because of a dense venous plexus.  Mucosa is less mobile than in the upper part of the anal canal.
FEATURES OF LOWER CUTANEOUS PART  This is about 8mm long.  Below the Hilton’s line.  Lined by true skin containing sebaceous glands  Epithelium of the lowest part resembles that of pigmented skin in which sebaceous glands, sweat glands, and hairs are present.
MUSCULATURE OF ANAL CANAL  ANAL SPHINCTERS  A ring of muscle surrounding and serving to guard or close an opening or tube. 1. INTERNALANAL SPHINCTER  Involuntary in nature.  Formed by the thickened circular muscle coat.  Surrounds the upper 3/4th i.e. 30mm of the anal canal upto Hilton's line.
2. EXTERNAL ANAL SPHINCTER  Voluntary in nature.  Made up of striated muscle.  Surrounds the whole length of anal canal.  Has 3 parts:-  DEEP PART  Surrounds the upper part of internal sphincter.
 SUPERFICIAL PART  Surrounds the lower part of internal sphincter.  Arises from the tip of coccyx and anococcygeal raph behind and inserted into the perineal body in front.  SUBCUTANEOUS PART  Lies below the internal sphincter.  Surrounds the lower part of anal canal.
CONJOINT LONGITUDNAL COAT  Formed by fusion of the puborectalis with the longitudinal muscle coat of the rectum at the anorectal junction.  Become fibroelastic at the level white line.  Breaks into fibroelastic septa which spread out fan-wise.  Pierces the subcutaneous part of external anal sphincter.  Attached to the skin around the anus called as corrugator cutis ani.
 ANORECTAL RING  Muscular ring present at the anorectal junction.  Formed by fusion of the puborectialis, deep fibres of external sphincter and the internal sphincter.  It is easily felt by finger in anal canal.
MCQS 1. Anal valves is present in which part of anal canal. a) Upper part b) Middle part c) Lower part d) All of the above 2. Following structure form the Anorectal ring except. a) Deep external sphincter b) Internal sphincter c) Puborectalis d) Conjoint longitudinal coat
Anal canal: features and relation