The large intestine, commonly known as the colon, represents the final stage of the human digestive process. While the small intestine handles the bulk of nutrient absorption, the colon is responsible for transforming liquid digestive residue into solid waste. It plays a significant role in managing the body’s fluid balance and preparing materials for elimination. This muscular tube reclaims remaining water and electrolytes, consolidating waste before it is expelled.
Defining the Transverse Colon’s Position
The transverse colon is the longest and most mobile section of the large intestine, spanning horizontally across the upper abdomen. It begins on the right side of the body at a sharp bend known as the hepatic flexure, or right colic flexure, which is situated just beneath the liver. From this point, the colon travels across the abdominal cavity in a somewhat downward-curving arch.
This section earns its name because it lies perpendicular to the rest of the digestive tract, moving from the right side toward the left. It terminates at the splenic flexure, or left colic flexure, a second sharp bend located high up near the spleen. The splenic flexure is often more securely anchored to the diaphragm by the phrenicocolic ligament, making it less mobile than the hepatic flexure.
The transverse colon is considered an intraperitoneal structure, meaning it is suspended within the abdominal cavity by a double layer of peritoneum called the transverse mesocolon. This mesentery connects the colon to the posterior abdominal wall and the inferior border of the pancreas, providing both support and a pathway for blood vessels. Due to this suspension, the transverse colon can vary in its exact position, sometimes dipping low into the lower abdomen.
Essential Functions in Waste Processing
The primary role of the transverse colon is to finalize the process of turning liquid chyme into solid stool. This is achieved through the absorption of residual water and salts from indigestible material. Although the small intestine absorbs up to 90% of ingested water, the colon reclaims the final remaining volume.
This segment also participates in microbial fermentation, carried out by trillions of bacteria residing within the large intestine. These commensal bacteria break down undigested carbohydrates and fiber, producing short-chain fatty acids (SCFAs) that the colon absorbs and uses as an energy source. The bacteria also synthesize certain vitamins, including Vitamin K and B vitamins like biotin, which are then absorbed into the bloodstream.
Movement of waste through the transverse colon occurs via two main types of contractions: haustral contractions and mass movements. Haustral contractions are slow, mixing movements that expose the fecal residue to the mucosal wall to enhance water and electrolyte absorption. Periodically, strong, coordinated peristaltic waves known as mass movements sweep the contents rapidly forward, propelling the forming feces toward the descending colon and ultimately the rectum for storage and elimination.
Notable Conditions Associated With This Segment
Several health issues can affect the transverse colon, disrupting its function and structure. Colorectal cancer can develop here, where malignant polyps grow into the lining of the bowel. The location of a tumor influences symptoms and treatment approaches.
Another concern is diverticulitis, though it is less common here than in the sigmoid colon. Diverticulosis involves the formation of small, bulging pouches called diverticula in the colon wall; diverticulitis occurs when these pouches become inflamed or infected. This inflammation causes abdominal pain and changes in bowel habits, which may occasionally be mistaken for other conditions.
A more acute, though rare, mechanical issue is volvulus, which involves the twisting of a loop of the intestine around its mesentery, leading to an obstruction. While volvulus most frequently affects the sigmoid colon or cecum, the transverse colon’s long and mobile mesocolon can predispose it to this torsion. If the twist is severe, it can cut off blood supply, requiring immediate medical intervention.