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Small & Large Intestine
Abdomen, Pelvis & Perineum Unit
Lecture 6
‫ حيدر جليل األعسم‬.‫د‬
Small Intestine: (Jejunum and Ileum)
• 6 m long. Upper 2/5 make up jejunum & lower 3/5 is ileum.
• Jejunum begins at DJ junction & ileum ends at ileocecal junc.
• Distinctive features, but a gradual change from one to other.
• They are freely mobile & are attached to post. abdominal
wall by fan-shaped mesentery.
• Root of the mesentery permits
entrance & exit of branches of
superior mesenteric artery and
vein, lymph vessels and nerves.
• Small intestine wall contains
plicae circulares, which are
larger, more numerous, and
closely set in jejunum, While
in the upper part of the ileum
they are smaller and more widely
separated and in the lower part
they are absent.
Differences between jejunum & ileum
1.Jejunum lies in upper part of peritoneal cavity below left side of
transverse mesocolon; ileum is in lower part of cavity and in pelvis.
2.Jejunum is wider bored, thicker walled, and redder than the ileum.
3.Jejunal mesentery is attached to post. abdominal wall above and to
left of aorta, whereas ileal mesentery is attached below and to right
of aorta.
4.Jejunal mesenteric vessels form only 1 or 2 arcades, with long and
few branches to intestinal wall. While ileum receives many short
terminal vessels from a series of 3 or 4or even more arcades.
5.In the jejunal mesentery, fat is deposited near root and is scanty
near intestinal wall; while at ileal mesentry, fat is deposited
throughout mesentery.
6.Aggregations of lymphoid tissue (Peyer's patches) are present in
mucous membrane of lower ileum along anti-mesenteric border.
These may be visible through wall of ileum from outside.
Blood Supply
Arteries: Superior mesenteric artery. Lowest part of
ileum is also supplied by the ileocolic artery.
Veins: Superior
mesenteric vein.
Lymph Drainage:
Superior mesenteric
nodes.
Nerve Supply:
sympathetic and parasympathetic (vagus).
Meckel's diverticulum
•It is remnant of proximal part
of the yolk stalk (vitelline
duct), which extends into the
umbilical cord in embryo and
lies on antimesenteric border
of ileum.
•Rule of 2:
2 inches long, occurs in 2% of
population and about 2 feet
from ileocecal junction.
•May produce symptoms in a
small number of patients
(Meckel’s Diverticulutis)
Large Intestine
It extends from ileum to anus and is divided into
cecum, appendix, ascending colon, transverse colon,
descending colon, sigmoid, rectum & anal canal.
Function of large intestine
is absorption of water and
electrolytes and storage of
undigested material until
expelled from body as feces.
Longitudinal muscle of the
colon is restricted to three
flat band called teniae coli.
Cecum
It is a blind-ended pouch situated in right iliac fossa and lies
below level of ileocecal junction. It is completely covered with
peritoneum and considerably mobile. Peritoneal folds create
superior ileocecal, inferior ileocecal, and retrocecal recesses.
Attached to its posteromedial surface is appendix. teniae coli
of the cecum converge on base of appendix and provide it
with a complete longitudinal muscle coat. Ileocecal opening is
provided with two folds, or lips, which form ileocecal valve.
Relations of the cecum:
Anteriorly: Small intestine,
greater omentum & anterior
abdominal wall in right iliac
fossa.
Posteriorly: Appendix (commonly),
Psoas and iliacus muscles,
femoral & lateral cutaneous
nerve of thigh.
Medially: Appendix arises from
the cecum on its medial side.
Blood Supply of cecum
Arteries: Anterior & posterior cecal arteries form
ileocolic artery (branch of superior mesenteric artery)
Veins: Drain into superior mesenteric vein.
Lymph drainage: Superior mesenteric nodes.
Nerve Supply: Sympathetic and parasympathetic
(vagus) nerves form superior mesenteric plexus.
ileocecal Valve
It consists of 2 horizontal folds of mucous membrane
that project around orifice of ileum. It plays little or no
part in prevention of reflux of cecal contents into
ileum; while circular muscle of lower end of ileum
(ileocecal sphincter) serves as a sphincter to controls
flow of contents from ileum into colon.
Appendix
It is a narrow, muscular tube containing a large amount of lymphoid
tissue. Its length from 8 to 13 cm (sometimes 20 cm). Its base is attached
to posteromedial surface of cecum about below ileocecal junction and
remainder is free. It has a complete peritoneal covering (attached to
mesentery of small intestine by a short mesentery (mesoappendix) that
contains appendicular vessels and nerves.
Arteries: appendicular artery (branch of
posterior cecal artery).
Veins: appendicular vein drains into
posterior cecal vein.
Lymphatics: Superior mesenteric nodes.
Nerve Supply: sympathetic &
parasympathetic (vagus) nerves
from superior mesenteric plexus.
(Referred pain to umbilicus)
T10 (umbilical region pain)
Appendectomy Operation
Appendix lies in right iliac fossa and its base is situated at
(McBurney's point) 1/3 of line joining right anterior superior
iliac spine to umbilicus. Base of appendix is easily found by
identifying the teniae coli of cecum and tracing them to base
of appendix, where they converge.
Common Positions of Tip of Appendix:
(a) Pelvic position: hanging down into
pelvis against right pelvic wall.
(b) Retrocecal position: coiled up
behind cecum.
(c) Paracecal position: projecting
upward along lateral side of cecum.
(d) Pre-ileal or Retro-ileal postion:
in front of or behind terminal part of
ileum.
Ascending Colon
It lies in right lower quadrant and extends upward from cecum to
inferior surface of right lobe of liver, where it turns to the left, forming
right colic flexure, and becomes continuous with transverse colon.
Peritoneum covers front and sides of ascending colon.
Relations:
Anteriorly: Coils of small intestine,
greater omentum & anterior abdominal wall.
Posteriorly: Iliacus, iliac crest, quadratus
lumborum, origin of transversus abdominis
Muscle & lower pole of right kidney. Iliohypogastric & ilioinguinal nerves cross behind it.
Blood Supply
Arteries: ileocolic & right colic branches of
superior mesenteric artery.
Veins: drain into superior mesenteric vein.
Lymph Drainage: Superior mesenteric nodes.
Nerve Supply: Sympathetic &parasympathetic
(vagus) nerves from superior mesenteric plexus.
Transverse Colon
It extends across abdomen, occupying umbilical region. It begins at right
colic flexure below right lobe of liver and hangs downward, suspended
by transverse mesocolon from pancreas. It then ascends to left colic
flexure below the spleen. Left colic flexure is higher than the right one
and is suspended from the diaphragm by phrenicocolic ligament.
Relations:
Anteriorly: Greater omentum &
anterior abdominal wall.
Posteriorly: 2nd part of duodenum,
head of the pancreas& jejunum & ileum.
Blood Supply:
Arteries: proximal 2/3 by middle colic
Artery (superior mesenteric artery).
Distal 1/3 by left colic artery (inferior
mesenteric artery).
Veins: Superior and inferior mesenteric veins.
Lymph Drainage: proximal 2/3 into colic nodes (superior mesenteric
nodes); distal 1/3 into colic nodes (inferior mesenteric nodes).
Nerve Supply: proximal 2/3 by Superior mesenteric plexus; distal 1/3
pelvic splanchnic nerves through inferior mesenteric plexus.
Descending Colon
It extends downward from left colic flexure, to pelvic brim, where it
becomes continuous with sigmoid colon. Peritoneum covers front &sides
Relations:
Anteriorly: Coils of small intestine, greater
Omentum & anterior abdominal wall.
Posteriorly: Lateral border of left kidney,
origin of transversus abdominis muscle,
quadratus lumborum, iliac crest, iliacus,
and left psoas. Iliohypogastric & ilioinguinal
nerves, femoral nerve & lateral cutaneous
nerve of thigh, lie posteriorly.
Blood Supply:
Arteries: left colic and sigmoid branches of
inferior mesenteric artery.
Veins: inferior mesenteric vein.
Lymph Drainage: inferior mesenteric nodes.
Nerve Supply: Sympathetic & parasympathetic
pelvic splanchnic nerves (inferior mesenteric plexus)
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