Transcript File

Rectum
 The rectum is about 12 cm long & upper part breath 4 cm
 Present in pelvic cavity
Position & Extent
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begins opposite SV3 as continuation of sigmoid colon
passes downwards, following curve of sacrum & coccyx
Then extends downwards forward about 2-3 cm in front & below tip
of coccyx
It abruptly turns downwards & backwards & is continuous with anal
canal at anorectal junction
Flexures
Flexures
Remarks
3 lateral
uppermost & lowermost flexures directed to the Rt
2 anteroposterior  the first follows curvature of sacrum = sacral
flexure ( convex backwards)
 the 2nd located at junction of rectum & anal canal
= perineal flexure (Convex forwards)
External Apperance
The rectum can be distinguished by
 absence of mesentery & appendices epiploicae
 absence of sacculations
 teniae coli to form longitudinal muscle coat
Peritoneum
Posterior surface of rectum is entirely non-peritoneal
upper 1/3
middle 1/3
lower 1/3
peritoneum covers ant & lat surfaces
peritoneum covers ant surface only
uncovered
Visceral relation Relations (Anteriorly, In the male)
Upper 2/3
1. rectovesical
pouch
lower 1/3 (devoid of peritoneum)
1. Base of Urinary Bladder
2. Terminal parts of Ureter
3. Vas Deferens
4. seminal vesicles
5. prostate
In the female
Upper 2/3 (covered by peritoneum) Lower 1/3 (devoid of peritoneum)
1. rectouterine pouch
1. Lower part of vagina
Posteriorly
 Lower 3 pieces of Sacrum, Coccyx & Anococcygeal Ligament
 Piriformis, levator ani & coccygeus
 Superior, Median & Lower lateral sacral vessels
 Sympathetic trunk
 Pelvic splanchnic nerves
Interior of Rectum
Mucous membrane of empty rectum shows two types of folds
Longitudinal fold: - Are transitory.
 Present in lower part of empty rectum & obliterated by distension
Transverse fold - Permanent
 More marked in distended rectum
Upper fold –
 Near the upper end of rectum & projects from Rt. or Lt. Wall
Middle Fold
 Largest & most constant lies in upper end of rectal ampulla & projects
from anterior & Rt. Walls
Lowest Fold
 Lies 2.5 cm below middle fold & projects from left wall
Blood Supply
Artery
 sup rectal art - Continuation of Inferior mesenteric artery
 middle rectal art - Branch of Internal Iliac Artery
 median sacral art - Branch of Abdominal Aorta
Venous Drainage
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follow arteries
however free anastomosis exist between
the superior, middle & inferior rectal veins
Nerve Supply
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Sympathetic from L1, L2
Parasympathetic from S2-S4
Anal Canal
The anal canal is about 3.8 cm long
 begins at level of anorectal junction as a continuation of the rectum
 passes downwards & backwards
 opens at anal orifice in the perineum
Pecularities
 Anterior wall of canal is shorter than Posterior wall
 Surrounded by Sphincter ani muscles, the tone of which keeps canal
closed except during daefecation
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Internal Apperance
Divided into 3 parts
 Upper part = 15 mm
 Middle part = 15 mm
 Lower part = 8 mm
Upper Part of Anal Canal
 lined by mucous membrane (columnar epithelium)
 mucosa thrown into vertical folds called anal columns
 joined at their lower ends by small semilunar folds called anal valves
 The anal valves together form a transverse line that runs all round
anal canal called pectinate line
Middle Part
 The upper part is separated from the lower part by the pectinate line
 Lined by Mucous membrane (stratified squamous epithelium but no
sweat & sebaceous gland)
 anal columns are absent
 Bluishish in Colour due to deep venous plexus
 The lower limit of this zone is whitish in appearance so it is referred as
white line of Hilton
Lowest part
 Cutaneous – lined by skin containing sweat & sebaceous gland
Sphincters
Internal anal sphincter
 Formed by circular muscle
fibres of the rectum
 Extends from upper end to
white line of Hilton
 involuntary
External anal sphincter
 Formed by of striated muscle
 Surrounds whole length of canal
 voluntary
 consist of 3 parts- deep part, superficial
part, subcutaneous part
Subcutaneous part
 Lies below the level of internal sphincter & surrounds lower part of
anal canal
 Is in form of flat band about 15 mm broad
Superficial part
 Surrounds lower part of internal sphincter
Deep part
 Surrounds upper part of internal sphincter
Blood Supply, Venous Drainage, Lymphatic Drainage & Nerve Supply
Arterial Supply
Venous Drainage
Nerve Supply
Above Pectinate Line
superior rectal artery
superior rectal vein
Lower Pectinate Line
inferior rectal artery
inferior rectal vein
Sympathetic (L1 & L2)
somatic supply via
Parasympathetic S2, S3 & (S2, S3, S4 )
S4)
Histological Structure of Large Intestine
 Mucosa
 Mucus surface – Is lined by simple columnar epithelium &
numerous goblet cells
 Absence of villus
 Lamina Propria – Is loaded with numerous deep & straight glands
with innumerable mucus goblet cells, lymphatics, smooth muscle
fibres & elastic fibres
 A thin layer of muscularis mucosa
 Sub – mucosa Loose areolar tissue, abundant adipose tissue & blood
vessels
 Muscularis Inner Circular & outer longitudinal smooth muscle
 Serosa - Peritoneum