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Anatomy of anal canal

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MEDICAL.. ANATOMY.. SURGICAL.. CLINICAL IMPORTANCE

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Anatomy of anal canal

  1. 1. ANATOMY OF ANAL CANAL Presented by : AYESHA JALIL Roll# 43
  2. 2. What is ANAL CANAL?
  3. 3. SURGICAL ANATOMY  The anal canal is about 1.5”(4 cm) long, commences at the level where the rectum passes through the pelvic diaphragm, downward and backward from rectal ampulla and ends at the anal verge
  4. 4. LOCATION  PELVIS  PERINEUM  ANAL TRIANGLE
  5. 5. RELATIONS POSTERIORLY Anococcygeal body LATERALLY Ischiorectal fossas
  6. 6.  ANTERIORLY IN MALE  Perineal body  Urogenital diaphragm  Membranous part of urethra  Bulb of penis  ANTERIORLY IN FEMALE  Perineal body  Urogenital diaphragm  Lower part of vagina
  7. 7. STRUCTURE  EMBRYOLOGY
  8. 8. INTERIOR OF ANAL CANAL Divided by pectineal line & Hilton’s line into 3 areas 1. Upper (15 mm) 2. Intermediate (15 mm) 3. Lower (8 mm) (Anal verge) Pectinate / dentate line Hilton’s line
  9. 9. UPPER HALF(2/3) LOWER HALF(1/3) STRUCTURE  Mucous membrane of upper half of anal canal is derived from hindgut entoderm.  It is lined by columnar epithelium  It is thrown into vertical folds called anal columns, which are joined together at their lower end by semilunar folds called anal valves(remains of proctodeal membrane).  Nerve supply is derived from autonomic hypogastric plexus. It is sensitive to stretch only.  Mucous membrane of lower half is derived from ectoderm of anal pit.  It is lined by stratified squamous epithelium.  There are no anal columns • The nerve supply is from somatic inferior rectal nerve.; it is thus sensitive to pain, temperature, touch and pressure.
  10. 10. BLOOD SUPPLY
  11. 11. VENOUS DRAINAGE
  12. 12. LYMPHATIC DRAINAGE
  13. 13.  The arterial supply is that of hindgut- superior rectal artery, branch of inferior mesenteric artery.  The venous drainage is by the superior rectal vein, a tributary of inferior mesenteric vein, and the portal vein.  The lymphatic drainage is to the pararectal nodes and then eventually to inferior mesenteric nodes.  The arterial supply is inferior rectal artery, a branch of internal pudendal artery.  The venous drainage is by inferior rectal vein, a tributary of the internal pudendal vein, which drains into the internal iliac vein.  The lymphatic drainage is downward to the medial group of superficial inguinal nodes.
  14. 14. NERVE SUPPLY
  15. 15. IMPORTANT!!!  When considering metastasis of cancer cells, tumors in superior part are painless, and those in inferior part painful.
  16. 16. MUSCULARIS EXTERNA  As in the upper parts of GIT, it is divided into an outer longitudinal and inner circular layer of smooth muscle.
  17. 17. ANAL FOLDS AND COLUMNS  The mucosa and submucosa above the dentate line is uneven and thrown into folds, the so-called anal cushions. there are usually three, the left lateral, right posterior and right anterior positions, and they continue proximally as the primary rectal foldings. Secondary foldings (the rectal columns of Morgagni) lie both over and between the primary folds.
  18. 18. MUCOSA SUSPENSORY LIGAMENT  the increased density of fibres that insert into the mucosa of the anal crypts at the level of the dentate line, termed the ‘mucosal suspensory Ligament.
  19. 19. INVOLUNTARY INTERNAL VOLUNTARY EXTERNAL ANAL SPHINCTERS  2-5 mm of thickening of the smooth muscle of the circular coat at the upper end of the anal canal.  Supplied by autonomic plexus and remains in tonic state of contraction.  It has three parts  Subcutaneous  Superficial  Deep  Supplied by pudendal nerve.
  20. 20. ANORECTAL RING  At the junction of rectum and anal canal, the internal sphincter, the deep part of external sphincter, conjoined longitudinal muscle and puborectalis muscles form anorectal ring.
  21. 21. INTERSPHINCTERIC PLANE  Between the external sphincter muscle laterally and the longitudinal muscle medially exists a potential space, the intersphincteric plane.  IMPORTANCE  Contains anal glands  Route for spread of pus  The plane can be opened up surgically to provide access for operations on the sphincter muscles.
  22. 22. HILTON’S LINE ALSO CALLED WHITE LINE/ANOCUTANEOUS INE. It is a color contrast bet’ bluish pink area above and black skin below. The line is represented by inter-sphincteric groove at the lower end of the internal sphincter . Indicates lower end of internal sphincter. Ischiorectal abscess when communicates with anal canal usually opens at or below Hilton’s line.
  23. 23. ANAL GLANDS  Anal glands may be found in the submucosa and intersphincteric space, and normally number between 0 and 10 in an individual.  Their function is unknown, although they secrete mucin. which perhaps lubricates the anal canal to ease defaecation.  The importance of intersphincteric anal glands is that they are widely considered to be the potential source of anal sepsis, either acute, presenting as perianal, ischiorectal or even pelvic sepsis, or chronic, presenting as a cryptoglandular (non-specific) anal fistula.

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