Large Intestine & Inferior Mesenteric Artery

Objectives

• Discuss anatomical structure of large intestine.

• Enlist the characteristic features of large intestine.

• What are the different positions of the Appendix.

• Describe the blood supply of the large intestine.

• The large bowel may vary considerably in length in different subjects;the average is approximately 5 feet (1.5 m).

• The large intestine is subdivided, for descriptive purposes, into:

• Caecum with the Appendix vermiform• Colon ascending colon hepatic flexure transverse colon splenic flexure descending colon sigmoid colon• Rectum & Anal canal .

Large Intestine

• The general characteristics of most of the large intestine are:

• Its large internal diameter compared to that of the small intestine;

• the appendices epiploicae (omental appendices) are fat-filled peritoneal tags

• The taeniae coli: three thickened bands of muscles• the haustra of colon are sacculations of the colon

between the taeniae

• No taeniae in the appendix or rectum.• The colon (but not the appendix, caecum or

rectum), bears characteristic fat-filled peritoneal tags called appendices epiploicae scattered over its surface.

• These are especially numerous in the sigmoid colon.

• The transverse colon and sigmoid are completely peritonealized (the former being readily identified by its attachment to the greater omentum).

• The ascending and descending colon have no mesocolon but adhere directly to the posterior abdominal wall . • The caecum is usually completely

peritonealized, • The appendix has its own mesocolon.

Features of large intestine:

Taeniae Coli: Three thickened bands of musclesNo taeniae in the appendix or rectumHaustra: Sacculations of the colon between the taeniaeOmental Appendices:Small fatty projections of the omentumCaliber:The internal diameter is much bigger than small intestine

Cecum and Appendix

IleocecalJunction

Taenia Coli

Sacculations=Haustra

• The cecum is that part of the large intestine that lies below the level of the junction of the ileum with the large intestine . It is a blind-ended pouch that is situated in the right iliac fossa. It is about 2.5 in. (6 cm) long and is completely covered with peritoneum.

• The appendix is attached to the posteromedial wall of the cecum, just inferior to the end of the ileum

• The appendix is suspended from the terminal ileum by the mesoappendix, which contains the appendicular vessels .

• Its point of attachment to the cecum, the base of the appendix, is consistent with the highly visible free taenia leading directly to it.

• But the location of the rest of the appendix varies considerably .

• The appendix is at the junction of the lateral and middle one-thirds of a line from the anterior superior iliac spine to the umbilicus (McBurney's point).

Variations in position Vermiform Appendix

64%

Variations in position Vermiform Appendix

Inferior mesenteric artery

Branches: 1. Left colic artery 2. Several sigmoid arteries 3. Superior rectal artery

• The inferior mesenteric artery and arises anterior to the body of vertebra L3. Its branches include the • left colic artery, • several sigmoid arteries, • superior rectal artery. • The veins drain into the inferior

mesenteric vein