Large Intestine- Structure And Function

LARGE INTESTINESTRUCTURE AND FUNCTION STRUCTURE Ø The term large intestine comes from the Latin term “Intestium crassum”. Ø It is the last part of digestive systemfinal stage of the alimentary canal-in vertebrate animals. Ø It is about 4.9 feet long(app.5 ft) and 2.5 cm in diameter.

Ø It is about one-fifth of the whole length of the intestinal canal. Ø It consists of the cecum,colon,rectum and anal canal. Ø It starts in the right iliac region of the pelvis ,just at or below the right waist, where it is joined to the bottom end of the small intestine(ileocecal junction).From here it continues up the abdomen, then across the width of the abdominal cavity, and then it turns down, continuing to its endpoint to the anus. Ø The wall of the large intestine is lined with

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COMPARING LARGE INTESTINE WITH SMALL INTESTINE

Ø Large intestine is wider than small intestine and differs in showing the longitudinal layer of the muscularis have been reduced to 3 strap- like structures known as y the taeniae coli. Ø Instead of having the evaginations of the small intestine (villi) the large intestine has invaginations (the intestinal glands). Ø While both the large and small intestine have goblet cells, they are abundant in large intestine. Ø Instead of having the evaginations of the small intestine (villi) the large intestine ha s invaginations (the intestinal glands). Ø While both the large and small intestine have goblet

STRUCTURE OF LARGE INTESTINE

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Ø The vermiform appendix , about 8-9 cm is attached to posteromedial surface of the large intestine. Ø It contains masses of lymphoid tissue. Ø It is a part of mucosa-associated lymphoid tissue which gives the appendix an important role in IMMUNITY. Ø Appendicitis is the result of a blockage that traps infectious material in the lumen. Ø The appendix can be removed with no

• On the surface , bands of longitudinal muscle fibers called taeniae coli, each about 5mm wide, can be identified. • There are 3 bands and they start at the base of the appendix and extend from the cecum to the rectum. Along the sides of the taeniae, tags of peritoneum filled with fat, called epiploic appendages are found. The sacculations, called haustra, are characteristic feature of the large intestine and distinguish it from the rest of the parts.

• Parts of the large intestine are: • Cecum –it is the first part of the large intestine. • Taeniae coli-three bands of smooth muscles. • Haustra –bulges caused by contraction of taeniae coli. • Epiploic appendages-small fat accumulations on the viscera.

FUNCTIONS OF LARGE INTESTINE • The major functions of the large intestine is to absorb water, nutrients and salts from the partially digested food that enters from the small intestine . • The large intestine takes 32 hours to finish up the remaining processes of the digestive system. food is not broken down any further in this stage of digestion. • The large intestine simply absorbs vitamins that are created by the bacteria inhabiting the colon. • It also absorbs water from the remaining indigestible food matter and compacts feces, and stores fecal matter in the rectum until eliminated through the anus

CECUM Ø It is the first part of the large intestine and is where the large and small intestines meet at the ileocecal junction. Ø The ileocecal junction or valve prevents packing up of fecal matter(stool) into the small intestine. Ø Attached to the cecum is tube called appendix; it has no known use in digestive processes.

COLON § § § § § § § §

The ascending colon The right colic flexure(hepatic) The transverse colon The transverse mesocolon The left colic flexure(splenic) Locations along the colon are: The descending colon The sigmoid colon-the v-shaped region of the large intestine

• Colon motility (the contraction of the colon muscles and the movement of its contents)is controlled by nerves, hormones and impulses in the colon muscles. • These contractions move the contents inside the colon toward the rectum . During this passage, water and nutrients are absorbed into the body and what is left over is stool. • The difference between the amount of fluid entering the colon from the small intestine and the amount of stool in the colon is what the colon absorbs each day.

• A few times each day contractions push the stool down the colon, resulting in a bowel movement. However ,if the muscles of the colon, sphincters and pelvis do not contract in the right way, the contents inside the colon do not move correctly; resulting in abdominal pain , cramps, constipation , a sense of incomplete stool movement or

RECTUM • It is a straight, muscular tube that begins at the end of the sigmoid colon and ends at the anal canal. • The anal canal is the last 2-3 cm of the digestive tract. The opening of the anal canal to the outside is called the anus.