The colon extends from the cecum to the rectum and consists of four parts: the ascending colon, transverse colon, descending colon, and sigmoid colon. It is supplied by branches of the superior and inferior mesenteric arteries and drains into the portal vein. The colon is innervated by the sympathetic and parasympathetic fibers of the autonomic nervous system.

1. Colon

2. Colon
• Extends superiorly from the cecum.
• Consists of 4 parts:
-ascending colon
-transverse colon
-descending colon
-sigmoid colon
• Ascending and
descending segments
are retroperitoneal and
transverse and sigmoid
segments are intraperitoneal.

3. Ascending Colon
• Lies in the right lower quadrant of trunk.
• It extends from the cecum, upward to the inferior surface
of right lobe of liver.
• At this position, it turns left to form the right colic
flexure and becomes continuous with the
transverse colon.
• The peritoneum covers the front and the sides of
the ascending colon and binds it to the posterior
abdominal wall.

5. Relations of ascending colon:
Anterior relations:
• Coils of small intestine
• Greater omentum
• Anterior abdominal wall
Posterior relations:
• Iliacus muscle
• Iliac crest
• Quadratus lumborum muscle
• Origin of transversus abdominis muscle
• Lower aspect of the right kidney
• Iliohypogastric and ilioinguinal nerves

6. • Blood supply:
Arteries
-ileocolic and
-right colic branches of the superior mesenteric artery
Veins
-The veins correspond to the arteries and eventually drain into
the superior mesenteric vein.
• Lymph drainage:
-The lymph vessels drain into lymph nodes lying along the course
of the blood vessels of the ascending colon. Ultimately the
lymph reaches the superior mesenteric lymph nodes.
• Nerve supply to ascending colon:
- receives sympathetic and parasympathetic nerves from the
superior mesenteric plexus.

7. Transverse Colon
• Passes from right
hypochondriac region into
left hypochondriac region.
• Extends from right colic
flexure to left colic flexure
below the spleen.
• The left colic flexure is
higher and more posterior
than the right colic flexure
,and is attached to the
diaphragm by the phrenicocolic
ligament.
• The transverse colon has its own
mesentery, known as the transverse
mesocolon. It suspends the transverse
colon from the anterior border
of pancreas.

8. Relations of transverse colon:
• Anterior relations:
-Greater omentum
-Umbilical and hypogastric
regions of anterior
abdominal wall
• Posterior relations:
-Descending part of the
duodenum
-Head of the pancreas
-Coils of jejunum and ileum
• superior relations –
– Liver
– Gall-bladder
– Greater curvature of stomach
– Lower end of spleen
• Inferior relations–
– Small intestine

9. • Blood supply:
Arteries
-proximal 2/3 by medial colic artery(branch of superior mesenteric
artery)
-distal 1/3 by left colic artery(branch of inferior mesenteric artery)
Veins
-The veins correspond to the arteries. Those from the proximal 2/3
drain into the superior mesenteric vein and those from the distal 1/3
drain into the inferior mesenteric vein.
• Lymph drainage:
-The lymph from the proximal 2/3 drain into the superior mesenteric
nodes, via the colic nodes.
-the lymph from the distal 1/3 drains into the inferior mesenteric
nodes, via the colic nodes.
• Nerve supply to ascending colon:
-The proximal 2/3 are innervated by sympathetic and parasympathetic
nerves from the superior mesenteric plexus.
-The distal 1/3 innervated by sympathetic and parasympathetic fibers
from the inferior mesenteric plexus.

10. Descending Colon
• lies at the left side of the
abdomen in both the upper
and lower quadrants.
• Begins at the left colic
flexure and ends by
becoming continuous with
the sigmoid colon, at the
pelvic brim.
• is covered from the front
and sides by the peritoneum,
which binds it to the posterior
abdominal wall.

11. Relations of descending colon:
• Anterior relations:
-Coils of small intestine
-Greater omentum
-Anterior abdominal wall
• Posterior relations:
-Lateral border of left
kidney
-Origin of transversus abdominis muscle
-Quadratus lumborum muscle
-Iliac crest
-Iliacus muscle
-Left psoas muscle
-Iliohypogastric and Ilioginuinal nerves
-Lateral cutaneous nerve of thigh
-Femoral nerve

12. • Blood supply:
Arteries
-left colic artery and
-sigmoid artery (branches of inferior mesenteric artery)
Veins
-The veins correspond to the arteries and eventually drain
into the inferior mesenteric vein.
• Lymph drainage:
-The lymph first drains into the colic lymph nodes, from
where it eventually drains to the inferior mesenteric
lymph nodes, which are situated around the root of
inferior mesenteric artery.
• Nerve supply to ascending colon:
- receives sympathetic and parasympathetic pelvic
splanchnic nerves through the inferior mesenteric plexus.

13. Sigmoid Colon
• Begins where descending
colon passes in front of the
pelvic brim. Below, it
becomes continuous with
the rectum at the level of S3.
• Completely surrounded
by peritoneum.
• Sigmoid colon is mobile
up to a certain extent.
• It hangs down into the pelvic
cavity in the form of a loop. It is
attached to the posterior wall of
the pelvis by a fan shaped fold of
peritoneum, known as sigmoid mesocolon. 1-lesser omentum 2-transverse mesocolon
3-small bowel mesentery
4-sigmoid mesentery

14. Relations of sigmoid colon:
• Anterior relations:
-Urinary bladder (in males)
-Posterior surface of uterus and
upper part of vagina (in females)
• Posterior relations:
-Lower coils of terminal
part of ileum
-Rectum
-Sacrum
-external iliac vessels
-left piriformis
-left sacral plexus of nerves

16. • Blood supply:
Arteries
-sigmoid branches of the inferior mesenteric artery.
Veins
-venous drainage through the inferior mesenteric
vein, which eventually drains into the portal venous
system.
• Lymph drainage:
-The nodes that receive lymph from
sigmoid colon lie along the course of the sigmoid
arteries. From these nodes, the lymph eventually
drains into the inferior mesenteric lymph nodes.
• Nerve supply to ascending colon:
-Inferior hypogastric plexus supplies both the
sympathetic and parasympathetic nerves.