The Large Intestine

Large Intestine

The large intestine consists of the cecum, the appendix; the ascending, transverse, descending, and sigmoid colon; the rectum; and the anal canal

Starts at the ileocecal valve & ends at the anus.

Absorption of water & electrolytes & storage of feces.

The large intestine can be distinguished from the small intestine by

• 1.Omental appendices: small, fatty, omentum-like projections.

• 2.Three taeniae coli: Presence of 3 bands of longitudinal smooth muscle called Taenia Coli.

Continued

• 3.Haustra: sacculations of the wall of the colon between the teniae

• 4.A much greater caliber (internal diameter).

Cecum

• The cecum is the first part of the large intestine that is continuous with the ascending colon.

• Approximately 7.5 cm in both length and breadth

• Cecum has no mesentery

• The terminal ileum enters the cecum obliquely and partly invaginates into it.

ileocecal valve

• ileocolic lips (superior and inferior) at the ileal orifice, which form the ileal papilla

• Arterial supply from the ant & post cecal arteries (branches of the ileocolic).

Appendix

• Worm shaped muscular tube containing lymphoid tissue.

• It arises from the posteromedial aspect of the cecum inferior to the ileocecal junction.

• The position of the appendix is variable, but it is usually retrocecal.

• The appendix has a short triangular mesentery, the mesoappendix.

Common Positions of the Appendix

Blood Supply of the Appendix

• Appendicular artery:branch of the posterior cecal, runs in the mesoappendix.

• Venous blood drains into the superior mesenteric.

• Visceral pain fibers enter spinal cord at T10.

Mc Burney’s point

For identification of the appendix – its base (tip of appendix is variable)

1.The base of the appendix lies deep to a point that is one third of the way along the oblique line joining the right ASIS to the umbilicus (the McBurney point on the spinoumbilical line).

2. Rt 1/3rd & L 2/3rd (McBurney’s point)

Pain in Appendicitis

• The initial pain in appendicitis is felt around the umbilicus region. This is referred pain via T10 segment of spinal cord

• Later on the inflammation involve the local peritoneum overlying the appendix in right iliac fossa. So pain is felt there.

Rovsing's sign• Rovsing's sign is a sign

of appendicitis.

• If palpation of the left lower quadrant of a person's abdomen increases the pain felt in the right lower quadrant, the patient is said to have a positive Rovsing's sign and may have appendicitis.

Psoas sign• A retrocecal appendix in a retroperitoneal

location may cause flank pain. • In this case, stretching the iliopsoas muscle can

elicit pain. • The psoas sign is elicited in this manner: the

patient lies on the left side while the examiner extends the patient's right thigh.

Obturator sign• Patient with a pelvic appendix may

show no abdominal signs.

• An obturator sign (pain on passive internal rotation of the flexed right thigh) may be present in a patient with a pelvic appendix.

Appendectomy

• Surgical removal of the appendix (appendectomy) is usually performed through a transverse or gridiron (muscle-splitting) incision centered at the McBurney point

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Appendectomy

Colon

• The colon is described as having four parts ascending, transverse, descending, and sigmoid that succeed one another in an arch

Colon• Ascending colon:

• Right iliac fossa to liver

• Hepatic flexure

• Secondarily retroperitoneal

• Transverse colon

• Approximately 45 cm long

• Hepatic flexure to splenic flexure

• Transverse mesocolon – mobile part of colon

Colon

• Descending colon

• Splenic flexure to left iliac fossa (sigmoid colon)

• Secondarily retroperitoneal

• Diverticulosis common

• Sigmoid colon

• Sigmoid mesocolon inverted V shaped

• Most common site for diverticulosis (60%)

Inferior mesenteric artery

• Branches.—Its branches are:   

• 1.Left Colic.2.Sigmoid.3.Superior rectal

Nerve supply

• The nerve supply to the cecum and appendix derives from the sympathetic and parasympathetic nerves from the superior mesenteric plexus.

• The left colic flexure also marks the divide between cranial (vagal) and sacral (pelvic splanchnic) parasympathetic innervation of the alimentary tract.

iIeostomy

Colostomy

Indications- Colostomy

Diverticulosis• Diverticulosis is a disorder in

which multiple false diverticula (external evaginations or out-pocketings of the mucosa of the colon) develop along the intestine.

• Diverticula may develop anywhere in the large intestine, but they are more common in the sigmoid colon, which is the last part of the large intestine just before the rectum.

•

Colonoscopy

References

• Clinically oriented anatomy 7th Edition – Keith L. Moore, Arthur F. Dalley, Anne M. R. Agur

• Google Images