2. • Is the part of elimentary canal continous
proximaly with sigmoid colon and distally with
anal canal.
• Rectosigmoid junction lies anterior to S3
vertebra.
• It follows the curve of sacrum and coccyx,
forming the sacral flexure of the rectum.
• Ends anteroinferiorly to the tip of the coccyx
by turning sharply posteroinferiorly to form
anorectal flexure
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3. • With the flexures of rectosigmoid junction
superiorly and the anorectal junction inferiorly
the rectum has an S shape when viewed
laterally.
• When viewed anteriorly it demonstrate three
sharp lateral flexures (superior,intermediate
and inferior) because of internal infoldings
(transverse rectal folds).
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4. The Ampula
• Dilated terminal part of the rectum,lies
directly above and supported by the
diaphragm( levetor ani).
• Receives and holds an accumulating feces
before expulsion.
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5. The peritoneum
• Peritoneum covers the anterior and lateral
surfaces of the superior third of the rectum, only
the anterior surface of the middle third and no
surface of the inferior third bcause it is
subperitoneal.
• In males peritoneum reflects from the rectum to
the posterior wall of the bladder to form the floor
of rectovesical pouch.
• In female to the posterior fornix of vagina to form
the floor of rectouterine pouch(cul-de-sac).
• In both sexes lateral reflections from superior
1/3rd of the rectum form pararectal fossae (
permits distention of the rectum)
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6. Relations :
• The rectum rest posterioly on the inferior three
sacral vertebrae and the coccyx, anococcegeal
ligament, median sacral vessels and inferior end
of sympathetic trunks and sacral plexuses.
• Males : anteriorly- fundus of urinary bladder
,terminal parts of the ureters ,ductus
deferentes,seminal vesicle and the prostate.
Rectovesical septum - fundus of ub and rectum.
• Female: Anteriorly- Vagina, separated from its
posterior fornix and cervix by rectouterine pouch.
Rectovaginal septum separates superior ½ of
posterior vaginal wall from rectum.
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7. Arterial blood supply
• Superior Rectal artery (IMA):
- supplies the proximal part.
• Two middle rectal artery ( Inferior versical a.)
- middle and inferior parts.
• Inferior rectal artery (internal pudendal artery) :
- supply the anorectal junction and anal
canal.
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8. Venous and lymphatic drainage :
• Blood from the rectum drains through
superior,middle and inferior rectal veins.
• Anastomosis btn portal and systemic vein occur
in the wall of anal canal.
• Note: - SRV- drain in portal venous system
-MRV & IRV- drain into systemic system
• The submucosal rectal venous plexus surrounds
the rectum and communicate with vesical venous
plexus in males and the uterovaginal venous
plexus in female.
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9. • Lymphatic vessels from superior ½ of the
rectum ascend along the superior vessels of
the pararectal lymphnodes the inferior
mesenteric and lumbar lymphnodes.
• From the inferior ½ , ascend with the middle
rectal arteries and drain into the internal iliac
lymphnodes.
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10. Innervation
• Sympathetic: Lumbar part of the sympathetic
trunk and the superior hypogastric plexus.
• Parasympathetic: Pelvic splanchic nerves,
fibers pass from these nerves to the left and
right inferior hypogastric plexuses to supply
the rectum.
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13. • Is the terminal part of the large intestines
• Extend from the upper part of the pelvic
diaphragm to the anus.
• 2.5cm to 3.5cm long
• Begins where the rectal ampulla narrows.
• Ends at the anus external outlet of the GIT
• Surrounded by internal and external anal
sphincter,descend posteroinferiorly btn
anococcygeal ligament and perineal body.
• It is collapsed except during passage of feces.
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14. • External anal sphincter; large voluntary
sphincter that forms a broad band on each
side of the inferior 2/3 of anal canal.
Blend superior with puborectalis muscle.
Supplied mainly by S4 through inferior rectal nerve.
• Internal anal sphincter; Is an involuntary
sphincter surrounding superior 2/3 of the anal
canal
Thickening of circular muscles, innervated by parasympathetic
fibers from pelvic splanchnic nerves.
Tonically contracted most of the time to prevent leakage of
gases and feces.
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15. The interior of anal canal
• Superior half of the mucus membrane is
characterized by a series of longitudinal ridges-
anal columns.
• The columns contains terminal branches of
rectal artery and vein. Anorectal junction
indicated by superior end of the anal columns.
• The inferior ends of the anal columns are
joined by anal valves. Superior to the valves
are small recesses –anal sinuses.
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16. When compressed by feces the anal
sinuses exudes mucus that aids in
evacuation of feces from the anal canal.
The inferior comb shaped limit of the
anal valves from an irregular line the
pectinate line that indicate the superior
part of the anal canal (derived from the
embryonic hindgut) and the inferior part
(derived from the embryonic
proctodeum)
*This difference make it different in
arterical, venous and lymphodic
17. Aterial supply of the Anal canal
•Superior rectal artery supply the anal
canal superior to the pectinate line.
•The two inferior rectal arteries supply the
interior part of the anal canal as well as
the surrounding muscles and perianal skin.
•Middle rectal form anastomosis with
superior and inferior rectal arteries.
18. Venous and lymphatic
•The internal rectal venous plexus drains in both
directions from the level of pectinate line.
•Superior to the pectinate line, the internal rectal
plexus drains chiefly into the superior rectal vein
(a tributary of the inferior mesenteric vein and
portal system).
•Inferior to the pectinate line, the internal rectal
plexus drains into the inferior rectal veins tributary
of caval venous system.
19. •The middle rectal vein-tributary of internal
iliac vein; drain the muscularis external of the
ampulla and form anastomosis with superior
and inferior rectal vein.
Lymphatic
Superior to the pectinate line the lymphatic
vessels drain into the internal iliac lymph
nodes and through them into the common iliac
and lumbar lymph nodes.
Inferior to the pectinate line, the lymphatic
vessels drain into the superficial inguinal
lymph nodes.
21. Innervation of the anal canal
•The nerve supply to the anal canal superior to
the pectinate line is visceral innervation from the
inferior hypogastric plexus(sympathetic and
parasympathetic fibres)
The superior part of anal canal is sensitive to
stretching only.
•The nerves supply inferior to the pectinate line
is somatic innervation derived from inferior anal
(rectal) nerves branches of pudendal nerve.
Hence sensitive to pain, touch and temperature.
23. Applied anatomy
• Rectal prolepses- Is a common clinical
condition, The partial prolepses - mucous
membrane and submucous coat protrude for
a short distance outside the anus. In complete
prolapses the whole thickness protrude
outside the anus (slidding hernia through pelvic diaphragm).
• Causes :
Birth injuries to levetor ani muscles
Aging associated with poor muscle tone.
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24. • Cancer of rectum-prone to lymphatic spread
to the adjacent structures.
ANAL CANAL
• Internal hemorrhoids; are vericosites
tributaries of supperior rectal (hemorrhoidal)
vein covered by mucous membrane.
• Causes:
• Congenital weakness of the vein walls
• Chronic constipation a/c prolonged straining during defecation.
• Pregnancy- gravid uterus exert pressure on superior rectal vein
• Portal hypertension due to liver cirrhosis
• Cancerous tumor blocking blood flow in supperior rectal vein.
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25. • Exaternal hemorrhoids; are varicosities of the
inferior rectal (hemorrhoidal) vein. Covered by
skin and are commonly a/c the well
established internal hemorrhoids.
• Causes not known: ?chronic cough? Straining?
• Perianal hematoma:Small collection of blood btn perianal skin.
• Caused by rupture of small subcutaneous vein
possibly by external hemorrhoid.
• Very painful.
• Anal fissure: Torn of the anal valves down to the anus.
• Caused by hard stool following chronic constipation.
• Very painful
• Occur commonly in midline posteriorly
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26. • Perianal abscess: Produced by fecal trauma to the anal mucosa.
Infection enter through small mucosal lesion
Infection of anal fissure
Infection of anal mucosal gland
The abscess may localized to :
• submucosa- Submucous abscess.
• Beneath perianal skin – subcutaneous abscess
• Ischeorectal fossae – ischeorectal abscess
• Btn ampulla and levetor ani- pelvirectal abscess
• Anal Fistula:Is due to spread or inadequate treatment of
anal abscess
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31. Histology
• General histology of GIT
Is a tube consisting of 4
histological layers:
mucosa
Submucosa
Muscularis
Serosa
• Just few modification
along its length.
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1) Mucosa
Epithelium – usually simple columnar with goblets; may be stratified
squamous if protection needed
Lamina propria - connective tissue deep to epithelium
Muscularis mucosae -produces folds - plicae (small intestine) or rugae
(stomach)
2) Submucosa – made up of loose connective tissue contains submucosal
plexus and blood vessels
3) Muscularis externa – smooth muscle, usually two layers (controlled by
the myenteric plexus ) -
outer layer: longitudinal
inner layer: circular
4) Serosa
visceral layer of mesentery or adventitia depending on location
33. Histology of large intestines
1. Mucosa - abundant goblet cells, stratified
squamous epithelium near anal canal
2. No villi
3. Longitudinal muscle layer incomplete, forms
three bands or taenia coli
4. Circular muscle - forms pockets or haustra
between bands
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