1. THE LARGE INTESTINE
• It extends from the ileum to the anus.
• It reabsorbs water converting liquid chyme into semi solid stools.
• It consists of the following parts: 1)Caecum and vermiformis
appendix. 2)Ascending colon and hepatic flexure. 3) Transverse colon
and splenic flexure 4)Descending colon 5)Sigmoid colon 6) Rectum
and 7) Anal canal.
• The proximal half as far as the splenic flexure – reabsorbs water and
electrolytes from fluid chyme .
• The distal colon beyond the splenic flexure-stores formed faeces until
they are excreted.
2.
3. 1. CONTINUATION…..
As the name implies ,the large intestine is wider than the small intestine.
-Other features : I ) taenie coli . 3 whitish longitudinal muscle bands which
start at the base of the appendix . These muscle bands pucker the large
intestine and with the activity of the circular layer of muscles forms haustra
or sacculations. 2)Appeandicess epiploicae- are fat filled pouches of serosa
that are scattered over the surface of the large intestine.
4. Caecum.
• A wide cul-de-sac of gut below the caecal sphincter.
• It lies in the right Iliac fossa .
• Commonly it is completely invested with peritoneum and hangs free.
Sometimes 2 vertical folds connect it to the posterior abdominal wall.
• It is the 1st. Part of the large intestine and continues with ascending
colon.
6. • The appendix is attached to the caecum to the point of convergence
of the 3 tenia . On the surface of the abdomen, this point lies at Mc
Burnys point, a point 1/3 way, the oblique line from anterior superior
iliac spine and the umbilicus. This point is constant ,and it signifies the
base of the appendix.
• The mesoappendix encloses the appendicular artery which is a
branch of the ileal caecal artery.
• Both the length and position of the appendix are variable. The
average length is 5cm, and the most common positions are
retrocaecal and pelvic.
7. The Ascending Colon
• Continuous with the upper end of the caecum and it extends up to
the hepatic flexure.
• It is retroperitoneal
• A peritoneal fold ,the Rt. Phrenico colic ligament connects the hepatic
flexure to the diaphragm.
• The Rt. Lateral paracolic gutter separates the colon from the
abdominal wall and the medial paracolic gutter is occupied by coils of
jejunum and ileum.
8. Transverse Colon
• It is approximately 15” .
• It begins at the hepatic flexure and arches across the abdomen to the
splenic flexure.
• It has a transverse meso colon.
• The splenic flexure is suspended from the diaphragm by the phrenico
colic ligament.
• Relations : Anteriorly coils of the small intestine and greater omentum.
Posteriorly –lateral border of the Left Kidney, the origin transversus
abdominis muscle and the Quadratus lumborum, iliac crest and the left
psoas muscle .The ILIO INGUINAL and Iliohypogastric nerves , the lateral
cutaneous nerve of thigh and the femoral nerve also lie posteriorly.
9.
10.
11. Descending Colon
• It extends from the splenic flexure to the pelvic brim.
• It is about 12 inches long.
• It is reteperitoneal.
• Its 3 tineae are in continuity with those of the transvers colon
• The appendicae are very numerous.
12.
13. Sigmoid colon.
• It is mobile and convoluted and has a mesentery. The root of the
mesocoln forms an inverted V attached along the pelvic brim and
then on the front of the sacrum.
• It is approximately 40 CM in length, but this is very variable, as it is a
storage organ for faeces.
• In the tropics ,people eat a lot of high residue diet, a “REDUNDANT
SIGMOID COLON “. This predisposes sigmoid volvulus.
14. Blood Supply .
• The colon gets its blood supply the superior and inferior mesenteric
arteries. The superior mesenteric artery is the artery to the mid gut. It
supplies colon up to the splenic flexure .
• THE inferior mesenteric artery is the smallest of the 3 trunks. I t is the
artery to the hind gut and supplies the colon from the splenic flexure to the
rectum.
• The branches of both superior and inferior mesenteric arteries supplying
the colon anastomose freely with each other and form the Marginal artery
of Drummond.
15.
16. Branches of superior mesenteric artery to the
colon.
• 1)The ileocolic artery-It from the R. side of the of the superior mesenteric trunk low
down in the base of the mesentery. It supplies the terminal ileum ,the appendix
vermiformis and the caecum. It anastomoses freely with the R. Colic branch.
• 2)The Right Colic branch.-Arises in the root of the mesentery from the right side of
Superior Mesenteric artery. It divides near the left side of the ascending colon into 2
branches :I )The descending branch runs down to anastomose with the colic branch of
the Ileocolic artery. Ii) The ascending branch runs up across the inferior pole of the R.
Kidney to the hepatic flexure where it anastomoses with a branch of the middle colic
artery. From these 2 branches, multiple versa recta sink into the wall of the ascending
colon to supply it.
• 3) The middle colic artery is the highest branch from right side of the S. mesenteric
artery. It divides into right and left branches. THE LEFT BRANCH supplies the transverse
colon to the splenic flexure ,where it anastomoses with L. colic artery. The R. branch
anastomoses with the R. colic artery ,and it supplies the transverse colon to the splenic
flexure.
17.
18. The inferior mesenteric artery
• It is the smallest of the 3 trunks. It gives 3 branches.
• 1)the left colic artery –supplies the descending colon from the splenic
flexure to the sigmoid colon
• The sigmoid branch –supplies the sigmoid colon.
• The superior rectal artery – supplies the rectum
19.
20. Venous drainage
• All the GIT is drained by the portal venous system to the liver.
• The names of the veins correspond with the named arteries.
• The ascending colon and transverse colon is drained by the superior
mesenteric vein.
• The sigmoid colon and descending colon ,drains into the inferior
mesenteric vein ,which in turn drains into the splenic vein.
21.
22. Lymphatic drainage
• Caecum ,ascending and transverse colon drain to the para colic nodes
to the Superior mesenteric group of lymph nodes to the pre aortic
lymph nodes.
• Descending colon and sigmoid colon drain into the inferior
mesenteric group of lymph nodes to the para aortic lymph nodes
