anatomy of rectum
TRANSCRIPT
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RECTUM
Dr Rishi PokhrelMBBS, MD
Maj
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LARGE INTESTINE
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• 3 unique features:
Teniae coli – Three bands of longitudinal smooth muscle
Haustrations – Pocket like sacs caused by tone of teniae coli
Epiploic appendages – Fat-filled pouches of visceral peritoneum
Subdivided into Caecum, Appendix, Colon, Rectum & Anal canal
LARGE INTESTINE
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Rectum
• Intro• Extent• Course & directions• Relations• Mucosal folds• Blood & nerve supply• Supports• Applied anatomy
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RectumTerminal part of large intestine before anal canalCardinal features of large intestine – absentLength – 12 cmDiameter – upper part 4 cm, lower part dilated
as rectal ampullaCurved in both sagittal and coronal planesFunction – temporary storage of fecal matter;
distension causes desire to defecate
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Extent Begins at S3, lower end of
sigmoid mesocolon – recto-sigmoid junction
Ends slightly below and 2-3 cm in front of tip of coccyx – anorectal junction
Males – at level of apex of prostate
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Course and directions
Anal canal
CURVATURES
Sacral flexure
Perineal flexure
Lat view AP viewupper
middle
lower
• Beginning and end lie in median plane• 2 AP curvatures
• Sacral flexure – follows curvature of sacrum and coccyx• Perineal flexure – backward bend in anorectal junction
• 3 lateral curvatures• Upper – convex to right• Middle – convex to left – most prominent• Lower – convex to right
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Peritoneal relations• Upper 1/3 – in front and sides• Middle 1/3 – only in front• Lower 1/3 – devoid of peritoneum
– Dilated to form ampulla– Below rectovesical pouch in males– Below recto uterine pouch in females
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Visceral relations• Anteriorly - in males
– Upper 2/3 – rectovesical pouch with coils of intestine
– Lower 1/3 – base of urinary bladder, ureters, seminal vesicle, vas and prostate
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• Anteriorly in females• Upper 2/3 – recto- uterine pouch with coils of intestine and
sigmoid colon, pouch separates the rectum from uterus and upper part of vagina
• Lower 1/3 – lower part of vagina
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Visceral relations
• Posterior in both sexes– Lower 3 sacrum, coccyx and anococcygeal ligament
– Piriformis, coccugeus and levator ani
– Median sacral, sup rectal and lower lat sacral vessels
– Sympathetic chain with ganglion impar, ant primary rami of S3-5, Co1, and pelvic splanchnic nerves
– Lymph nodes, lymphatics and fat
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POST. RELATIONS
Symp. chain
Piriformis
S-4 nerve & Lower lat. Sacral artery
CoccygeusS-5 nerve
Co-1 nerve
Levator ani
Median sacral A.
Ganglion imparCoccyx
Anococcygeal ligament
Sacrum
Rule of Three• 3 Bones & ligs.• 3 Muscles• 3 Vessels• 3 Sets of
nerves• 3 Other
structures
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Mucosal folds• 2 types of folds
– Longitudinal – temporary, in lower part, disappear on distension
– Transverse / Houston’s valves – permanent
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INTERIOR OF RECTUM: MUCOSAL FOLDS
Recto-sigmoid junction
Valves of HOUSTON
Anorectal junctionLevator ani
Peritoneal reflection
Upper fold• At commencement ( S-3)• 12 cm from anal orifice• From Rt. Lt. Ant. wall
Middle fold• Largest & most
constant• Projects from Rt. Wall• At jn. of upper 2/3 with lower 1/3• 5 cm above anal
margin• Forms Neleton’s
sphincterLower fold• Inconstant• Projects from Lt. wall• 2.5 cm below middle
fold
Fourth fold• May be present• 2.5 cm above M F• From Lt. wall
U
L
M
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TRANSVERSE MUCOSAL FOLDS
Midline
Upper end
Lower end
U
M
L
A
C
B
LUMEN
Middle Tr. fold
UpperTr. fold
LowerTr. fold
Three valves of rectum stop feces from being passed with gas
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TRANSVERSE MUCOSAL FOLDS
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Blood supply
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Venous drainage
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Lymphatic drainage
• Upper ½ - sup rectal vessels -> para rectal & sigmoid nodes -> inf mesenteric nodes
• Lower ½ - middle rectal vessels -> internal iliac nodes
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Nerve supply
• Sympathetic – L 1-2• Parasympathetic – S 2-4• Distension – Parasympathetic• Pain - both
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DEFECATION
• Distension of rectal walls caused by feces
– Stimulates contraction of the rectal walls
– Relaxes internal anal sphincter
• Voluntary signals stimulate relaxation of the external anal sphincter and defecation occurs
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Supports
• Pelvic floor by levator ani• Waldeyer’s fascia – lower part of rectal ampulla to
sacrum, contain sup rectal vessels and lymphatics• Lateral ligaments – contain middle rectal vessels,
nerves• Rectovesical pouch• Pelvic peritoneum• Perineal body
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APPLIED
PR EXAMPROCTOSCOPYRADIOLOGICAL STUDIESPROLAPSE AND INTUSUCEPTIONPOLYPCARCINOMA
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RECTUM: DOUBLE CONTRAST STUDYApplied anatomy
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RECTAL INTUSSUSCEPTION & RECTAL PROLAPSE
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PROLAPSE OF RECTUM
COMPLETE PROLAPSE
• Complete - consists of full thickness of rectal wall.
• Partial prolapse - only mucous membrane of rectal wall.
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RECTAL POLYP
• Growth or mass Protruding from the mucous membrane
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