Large Intestine Anatomy

Intestine is that portion of the digestive tract, that runs between the stomach to the anus. It is divided into the small intestine and large intestine. The small intestine forms a major part of the human intestine with a length of around six meters. It can be found in the center of the abdominal cavity. Large intestine starts at the point, where the small intestine ends. As compared to the small intestine, large intestine has more width, but is only 1.5 meters in length, which is around one fifth of the length of the intestinal canal. The large intestine consists of the cecum, ascending colon, transverse colon, descending colon and sigmoid colon. Scroll down for more details about large intestine anatomy.

Large Intestine Anatomy and Physiology

As mentioned earlier, large intestine starts from the point, where the small intestine ends. To be more precise, it starts from the right iliac region of the pelvis, which is located at the right waist or just below it. The large intestine starts with the cecum (where the end point of the small intestine opens into the large intestine) and travels upwards, and then runs across the abdominal cavity, again turns down to end with the sigmoid canal, which is followed by the rectum, anal canal and the anus. The portion of the large intestine that comes after the cecum and runs upwards is called ascending colon and that travels across the abdomen is called transverse colon. The descending colon follows the transverse colon and turns downward to end in sigmoid colon, which is followed by the rectum.

The large intestine is almost like an arch, which surrounds the coiled small intestine in the abdominal cavity. As a major part of the digestive process is done in the small intestine, the large intestine is left with the function of absorbing water and some vitamins. It is mainly responsible for storing the fecal matter, solidifying it by absorbing water and expelling it with the help of rhythmic contractions (peristaltic movements) of the intestinal muscles.

Cecum: The large intestine starts with the cecum, which is like a pouch in structure and connects the ileum (the last part of the small intestine) to the ascending colon. It is separated from the ileum by the ileocecal valve or Bauhin's valve and from the ascending colon by the cecocolic junction. It is about six centimeters in length and the vermiform appendix hangs from the cecum.

Ascending Colon: Ascending colon comes after the cecum and travels upwards till it reaches the hepatic flexure or right colic flexure, which is the turn of the colon near the liver. In other words, hepatic flexure is the bend between the ascending colon and the transverse colon. The transverse colon bends to form the hepatic flexure, which is followed by the transverse colon, which travels across the abdominal cavity.

Transverse Colon: The transverse colon starts from the right hepatic flexure and is the longest and the movable part of the large intestine. It is slightly curved downwards with a sharp upward rise near its end, where it bends downwards to form the left colic flexure or splenic flexure, which is located near the spleen. It is from this left colic flexure, the descending colon starts. The transverse colon is connected to the stomach by a band of tissues, which is known as the greater omentum. The posterior side of the transverse colon is attached to the posterior abdominal wall by peritoneum (the membrane that lines the abdominal cavity) and this attachment is called transverse mesocolon.

Descending Colon and Sigmoid Colon: The descending colon starts from the splenic flexure and ends at the beginning of the sigmoid colon. It is more deeply placed, as compared to the ascending colon and has some parts of the small intestine in front of it. It ends with the sigmoid colon, which is the last part of the large intestine, which ends at the point, where the rectum starts. Sigmoid colon is an S-shaped structure, which contains muscles, that contract to create a pressure in the colon, in order to expel the stools and move the stools to the rectum.

Now, you know more about small and large intestine anatomy, which may help you in understanding more about the functions of this organ. The main functions of the large intestine is to absorb water, store waste, absorption of some vitamins (like vitamin K), thickening and expulsion of the stools. The large intestine houses around 700 species of bacteria, which aids in the fermentation of the fibers in the food materials. These bacteria also produce large amounts of vitamins, like vitamin K and Biotin (a B vitamin), which is absorbed into the blood.