Anatomy of anal canal


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Anatomical description of anal canal

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  • Outer longitudinal Coat:At ano-rectal Jn. blends with Puborectalis (part of levatorani) forms conjoint fibro-elastic sheath, extends downwards bet’ sphincter aniexternus & internus muscles. At the lower end of the internal sphincter the sheath splits into a number of septa which pierce the subcutaneous part of the external sphincter muscle and are inserted into the peri anal skin. Thesefibres form so called corrugator cutis muscle. The medial most septum known as anal intermuscular septum, is attached to anal canal at the Hilton’s white line and is considered by some authors to produce the anal inter-sphincteric groove. Some of the septa spread are lost in the ischio-rectal fat.Circular muscle:Surrounds entire rectum and is thickened in the lower part to form sphincter aniinternus muscle which encircles upper three-fourths of the anal canal.
  • Anatomy of anal canal

    3. 3. STRUCTURE OF RECTUM Serous Muscular – Ouer Longitudinal - Inner circular Submucous Mucous
    4. 4. Anal canal Terminal part of alimentary tract Begins at ano-rectal junction Rectal ampulla suddenly narrows at ano-rectal junction 2-3 cms infront and slightly below Tip of coccyx From ano-rectal junction canal passes Downwards & backwards through Pelvic diaphragm Opens at anal orifice situated in the cleft between buttocks 4 cms below & in front of tip of coccyx.
    5. 5. Ano-rectal junction in male corresponds to apex of prostate 4 cms in front of tip of coccyx
    6. 6. Features Anterior wall shorter than posterior wall Surrounded by sphincter ani muscles Canal closed except during defaecation Measurements Length (adult) 3.8 cms Breadth when empty lateral walls approximated (antero-posterior slit)
    7. 7. RELATIONS In front: 1. Perineal body 2. In male – bulb of penis & spongy urethra In female – Lower part of post. wall of vagina Behind: Ano-coccygeal raphe Fibro-fatty tissue bet’ peri-anal skin & raphe On each side: Ischio-rectal fossa and its contents
    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. INTERIOR OF ANAL CANAL Anal column Anal valves (of Ball) Pectinate / dentate line - sentinal pile Anal papillae Anal sinuses Anal glands
    10. 10. Anal column Anal valves (of Ball) Pectinate / dentate line - sentinal pile Anal papillae Anal sinuses Anal glands
    11. 11. PECTINATE LINE Muco-cutaneous junction of anal canal Corresponds with position of anal valves Situated at the middle of internal sphincter Divides anal canal into upper and lower areas (proctodeum) which are different in development, blood supply, lymph drainage and in nerve supply
    12. 12. Distinction Above Pectinate line Below Pectinate line Destination of lymph drainage Internal iliac lymph nodes (pararectal lymph nodes) Superficial inguinal lymph nodes (Below Hilton’s line) Epithelium Columnar epithelium (as is most of the digestive tract – the line represents the end of the part derived from the hind gut) Stratified squamous epithelium , non keratinized (until Hilton’s white line, where the anal verge becomes continuous with the perianal skin containing keratinized epithelium) Embryological origin Endoderm Ecotoderm Artery Superior rectal artery Middle & inferior rectal arteries Vein Superior rectal vein Middle & inferior rectal veins Hemorrhoids classification Internal hemorrhoids (not painful) External hemorrhoids (painful) Nerves Inferior hypogastric plexus Symp L1,L2 & parasymp S2,S3,S4 Inferior rectal nerves
    13. 13. HILTON’S LINE 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 Anal intermuscular septum is attached carrying the fibres of levator ani and longitudinal muscle of rectum Anal fascia and lunate fascia extends upto this line Ischiorectal abscess when communicates with anal canal usually opens at or below Hilton’s line
    14. 14. HILTON’S LINE
    15. 15. ANAL GLANDS Floor of the sinus receives the ducts of the tubular anal glands, which ramify in the sub-mucous coat of the anal canal and sometimes penetrate the internal sphincter muscle. These glands are occasionally Infected and act as a source of anal fistula.
    16. 16. SPHINCTERS OF THE ANAL CANAL Two – Internal & external, surround the anal canal. SPHINCTER ANI INTERNUS Involuntary sphincter Thickening of circular muscle of lower part of rectum Surrounds upper 3/4th of anal canal Lower end corresponds with Hilton’s line Middle corresponds with pectinate line Internally the sphin. Is separated from mucous membrane by internal venous plexus Externally separated from ext. sphin. Muscle by Conjoint sheath derived from levator ani and longitudinal muscles of rectum Nerve supply: Sup.Hypogastric & pelvic splanchnic
    17. 17. SPHINCTER ANI EXTERNUS Voluntary sphincter Surrounds entire length of anal canal Consists of 3 parts – Subcuatneous Superficial & Deep Subcutaneous: Flat band around anus separated from perianal skin by external venous plexus Superficial part: Ellipical in shape Arises from tip of coccyx & anococcygeal raphe, inseted into perineal body Deep: annular in shape surrounds ano-rectal junction No bony attachment – inserted into perineal body Nerve supply: Inf. Rectal br. Of pudendal n. Perineal br. of 4th sacral n.
    18. 18. CONJOINT FIBRO – ELASTIC SHEATH Formed by longitudinal muscle of rectum blending at ano-rectal Junction with puborectalis part of leavto ani
    19. 19. CONJOINT FIBRO – ELASTIC SHEATH Formed by longitudinal muscle of rectum blending at ano-rectal Junction with puborectalis part of leavto ani
    20. 20. BLOOD SUPPLY
    24. 24. ANAL FISTULAE Fibrous tracts communicating with two surfaces Ano-rectal mucosa and skin Es – Extra-sphincteric fist. Ts – Trans-sphincteric fist. Sf – Superficial fist. Is – Inter-sphincteric fist. Ss – Suprasphincteric fist. Key : fist = fistula
    25. 25. Normal Veins Internal & external haemorrhoids
    26. 26. Sentinal pile is a tag formed by a ruptured anal valve
    27. 27. 11 O’ clock 7 O’ clock 3 O’ clock
    28. 28. PR - Per rectal examination