Surgical anatomy anal canal

2018

1. Surgical anatomy- anal canal by : Dr. Belal Mansoor Taiz university 18/3/2018

2. Overview Introductions Location , extent , Dimensions of anal canal Embryology The anorectal ring ,The puborectalis muscle Anal sphincters & The intersphincteric plane The epithelium and sub epithelial structures(internal). Blood supply , Lymphatic drainge ,& Nerve supply Clinical aspects

3. The anal canal The anal canal remains an area of medicine and surgery plagued by obscurity and limited provider knowledge. Many conditions are in fact common and benign, but some lead to incapacitating interference with the patient’s daily life . SABISTON TEXTBOOK of SURGERY 20 th EDITION

4. The anal canal Therefore, attempts to improve our fund of knowledge of the anatomy and function of the anal canal and the basic physiology of the pelvic floor. should facilitate accurate diagnosis and management of both common and rare conditions . SABISTON TEXTBOOK of SURGERY 20 th EDITION

5. The surgical anal canal The surgical anal canal: It begins at the anorectal junction terminates at the anal verge.

6. The surgical anal canal The muscular junction between the rectum and anal canal can be felt with the finger as a thickened ridge – the anorectal ‘ bundle’or ‘ ring’ . Bailey & Love’s 26 th EDITION

7. The surgical anal canal- Dimensions The surgical anal canal measures 2 to 4 cm in length and is generally longer in men than in women. Schwartz’s Principles of Surgery Tenth Edition

8. The anatomic anal canal The anatomic anal canal extends from the dentate or pectinate line to the anal verge.

9. Posteriorly : Anteriorly : In the male,: the perineal body, , the membranous part of the urethra, and the bulb of the penis

10. Anteriorly : In the female ,: the perineal body , the lower part of the vagina

11. Laterally: The fat-filled ischiorectal fossae

12. The anal canal below the pectinate line develops from the proctodeum (ectoderm), while that above the pectinate line develops from the endoderm of the hindgut.

13.   The congenital anomaly in which the anal canal fails to communicate with the exterior is known as imperforate anus. Imperforate anus is a congenital anomaly in which the anal canal fails (completely or incompletely) to open to the exterior.

14. The anal canal is completely extraperitoneal .

15. The Anorectal Ring The anorectal ring marks the junction between the rectum and the anal canal . It is formed by the joining of : the puborectalis muscle the deep external sphincter, conjoined longitudinal muscle the highest part of the internal sphincter

16. The Anorectal Ring

17. The anorectal ring The anorectal ring can be clearly felt digitally , as a thickened ridge , especially on its posterior and lateral aspects.

18. the puborectalis muscle At rest , the puborectalis muscle creates a “sling” around the distal rectum, forming a relatively acute angle that distributes intra-abdominal forces onto the pelvic floor. With defecation, this angle straightens , allowing downward force to be applied along the axis of the rectum and anal canal. Nonrelaxation of puborectalis results in straining and incomplete evacuation.

19. Anal sphincters

20. The external sphincter Voluntary sphincter Composed of skeletal muscle. Surrounds entire length of anal canal Consists of 3 parts – Subcuatneous Superficial & Deep Nerve supply: Inf. Rectal br. Of pudendal n. Perineal br. of 4th sacral n.

21. The external sphincter Consists of 3 parts The parts blend with one other to form a continuous tube.

22. The external sphincter The deep external anal sphincter : ring, together wiht the puborectalis muscle. Superficial : elliptical ,and attached to coccyx Subcutanenous :ring

23. Anorectal sphincter tone can be assessed during digital rectal examination (DRE) when the patient is asked to squeeze the examining finger. The external sphincter

24. The intersphincteric plane Between the external sphincter muscle laterally and the longitudinal muscle medially exists a potential space, the intersphincteric plane. The plane can be opened up surgically to provide access for operations on the sphincter muscles.

25. The longitudinal muscle The longitudinal muscle is a direct continuation of the smooth muscle of the outer muscle coat of the rectum.,

26. At the anorectal junction the outer longitudinal layer of rectal m. become fibro elastic and, together with some striated muscles fibres of puborectalis , forms he conjoint longitudinal coat which runs down between the two sphincters.

27. The internal sphincter When exposed during life, it is pearly - white in colour and its circumferentially placed fibres can be seen clearly.

28. The Defecation Defecation has four components: mass movement of feces into the rectal vault. rectal–anal inhibitory reflex , by which distal rectal distention causes involuntary relaxation of the internal sphincter; voluntary relaxation of the external sphincter mechanism and puborectalis muscle; increased intra-abdominal pressure.

29. The Continence Continence requires: normal capacitance, normal sensation at the anorectal transition zone, puborectalis function for solid stool , external sphincter function for fine control , internal sphincter function for resting pressure .

30. THE INCONTINENCE INCONTINENCE : is the inability to prevent elimination of rectal contents. Etiologies include : (1) mechanical defects , sphincter damage from obstetric trauma , fistulotomy , and scleroderma affecting the external sphincter; (2) neurogenic defects, spinal cord injuries, pudendal nerve injury due to birth trauma or lifelong straining, and systemic neuropathies such as multiple sclerosis; and (3) stool content-related causes, such as diarrhea and radiation proctitis .

31. Interior of anal canal

32. Interior of anal canal

33. Interior of anal canal

34. The anal valves join together the lower ends of the  anal columns

35. most important landmark both morphologically and surgically

36. The pectinate line The pectinate line is not seen on inspection in clinical practice , but under anesthesia the anal canal descends down, and the pectinate line can be seen on slight retraction of the anal canal skin.

37. The  anal sinuses  are furrows in the  anal canal , that separate the  anal columns  from one another. The anal sinuses end below in small valve-like folds, termed  anal valves .

38. The glands themselves are located at varying depths in the anal canal wall

39. The pecten : is a smooth area of hairless stratified epithelium that lies between the anal valves superiorly and the inferior border of the internal anal sphincter inferiorly.

40. ANAL FISSURE: it is a split in the anoderm . (a longitudinal tear in the mucosa and skin of the lower third of the anal canal). 90%occur posteriorly (comparatively low blood flow)

41. If surgery is required , lateral internal sphincterotomy is 90% successful. ANAL FISSURE

42. Blood supply The blood supply is based on embryology: ■ Hindgut : Inferior mesenteric artery (IMA) ■ Distal anus: Internal pudendal artery branches

43. arterial supply above dentate line:   superior rectal artery  (from  inferior mesenteric artery ); small contributions from  middle rectal artery   (directly from  internal iliac artery ) and  median sacral arteries below dentate line:   inferior rectal artery  (from  internal pudendal artery ).

44. venous drainage:  continuous with rectal venous plexus (i.e. rich anastomoses ). above dentate line:  superior rectal vein to  inferior mesenteric vein  (portal venous system) below dentate line :  inferior and middle rectal veins to  internal iliac veins The anal canal is a site of  portosystemic anastomosis . 

45. Haemorrhoids (‘piles’) Haemorrhoids (piles) are engorged vascular cushions found within the submucosa of the anal canal that exist in three columns in the anal canal: right anterolateral , right posterolateral , and left lateral.

46. Innervation above dentate line and internal anal sphincter Sympathetic L1,L2: from pelvic plexus ……. Cause contraction parasympathetic S2,S3,S4( cause relaxsion )and afferent sensory:  pelvic splanchnic nerves below dentate line and external anal sphincter inferior rectal branches  of the  pudendal nerve

47. last

48. SUMMARY The anorectal area consists of a relatively small but complex region where multiple anatomic and physiologic interactions occur to help aid continence and defecation .

49. References Short Practice Of Surgery Bailey & Love’s 26 th Edition Sabiston Textbook Of Surgery 20TH Edition Schwartz’s Principles Of Surgery Tenth Edition Netter’s Surgical Anatomy 2 ND Edition Clinical Anatmy BY Regions ,Snell 9 TH Edition Last Anatomy 2011 . Cracking The Mrcs Viva 2007. Slideshare ,Google .

50. THANK YOU