ANAL CANAL

TRIANGLES – PELVIC OUTLET

LEVATOR ANUS MUSCLES - COMPONENTS

STRUCTURE OF RECTUM

SerousMuscular – Ouer Longitudinal - Inner circularSubmucousMucous

Anal canal

Terminal part of alimentary tract

Begins at ano-rectal junction

Rectal ampulla suddenly narrowsat ano-rectal junction

2-3 cms infront and slightly belowTip of coccyx

From ano-rectal junction canal passesDownwards & backwards through Pelvic diaphragm

Opens at anal orifice situated in the cleft between buttocks 4 cms below & in front of tip of coccyx.

Ano-rectal junction in male corresponds to apex of prostate

4 cms in front of tip of coccyx

FeaturesAnterior wall shorter than posterior wallSurrounded by sphincter ani muscles Canal closed except during defaecation MeasurementsLength (adult) 3.8 cmsBreadth when empty lateral walls approximated (antero-posterior slit)

RELATIONS

In front:1. Perineal body2. In male – bulb of penis & spongy urethra In female – Lower part of post. wall of vagina

Behind:Ano-coccygeal rapheFibro-fatty tissue bet’ peri-anal skin & raphe

On each side:Ischio-rectal fossa and its contents

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

INTERIOR OF ANAL CANAL

Anal columnAnal valves (of Ball)Pectinate / dentate line - sentinal pileAnal papillaeAnal sinusesAnal glands

Anal columnAnal valves (of Ball)Pectinate / dentate line - sentinal pileAnal papillaeAnal sinusesAnal glands

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

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 arteriesVein Superior rectal vein Middle & inferior rectal veinsHemorrhoids classification

Internal hemorrhoids (not painful)

External hemorrhoids (painful)

Nerves Inferior hypogastric plexusSymp L1,L2 & parasymp S2,S3,S4

Inferior rectal nerves

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 sphincterAnal 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

HILTON’S LINE

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.

SPHINCTERS OF THE ANAL CANAL

Two – Internal & external, surround the anal canal.

SPHINCTER ANI INTERNUS

Involuntary sphincterThickening of circular muscle of lower part of rectumSurrounds upper 3/4th of anal canalLower end corresponds with Hilton’s lineMiddle corresponds with pectinate lineInternally the sphin. Is separated from mucous membrane by internal venous plexusExternally separated from ext. sphin. Muscle byConjoint sheath derived from levator ani and longitudinal muscles of rectum

Nerve supply: Sup.Hypogastric & pelvic splanchnic

SPHINCTER ANI EXTERNUS

Voluntary sphincter Surrounds entire length of anal canalConsists of 3 parts – Subcuatneous Superficial & DeepSubcutaneous: Flat band around anus separated from perianal skin by external venous plexusSuperficial part: Ellipical in shape Arises from tip of coccyx & anococcygeal raphe, inseted into perineal bodyDeep: 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.

CONJOINT FIBRO – ELASTIC SHEATHFormed by longitudinal muscle of rectum blending at ano-rectalJunction with puborectalis part of leavto ani

CONJOINT FIBRO – ELASTIC SHEATHFormed by longitudinal muscle of rectum blending at ano-rectalJunction with puborectalis part of leavto ani

BLOOD SUPPLY

VENOUS DRAINAGE

LYMPHATIC DRAINAGE

NERVE SUPPLY - SYMPATHETIC & PARASYMPATHETIC

ANAL FISTULAE

Fibrous tracts communicating with two surfacesAno-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

Normal Veins Internal & externalhaemorrhoids

Sentinal pile is a tag formed by a ruptured anal valve

11 O’ clock

7 O’ clock

3 O’ clock

PR - Per rectal examination