Transverse Colon: Definition & Function

Instructor: Rachel Torrens
The transverse colon is a part of the large intestines. In this lesson, learn the structural details, as well as the functionality of this important part of the digestive system.

Digestion: An Impressive Journey

You open your mouth wide and bite into a delicious slice of watermelon. You may think ''Yum!'', but within seconds your mind forgets about that particular bite. Well, that particular bite is going to be a part of you for approximately the next 36 hours. And that little bit of watermelon will cover a distance of approximately 30 feet in your digestive system!

From start to finish, the watermelon will travel through the body in this order: mouth, esophagus, stomach, small intestine, large intestine, and finally anus. The large intestine is comprised of the cecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum. In this lesson, we will focus on a very specific bit of that journey, namely the transverse colon, which represents about 18 inches of that 30 foot journey.

The large intestines is the last part of the digestive system in which components may be absorbed.
Large Intestine Diagram

The Transverse Colon

The transverse colon is the portion of the large intestine which crosses the upper abdomen from right to left. Obviously, it's dawning on you how this section of large intestines got its name. It's the only bit that transverses the abdomen from one side to the other, and thus, became known as the transverse colon.

Structure of the Transverse Colon

The transverse colon is rather like a large tube, the inner diameter of which is about 2.5 inches. However, the tube is not simply an open cylinder, but has band-like structures, which cinch the tube in periodically. The bulges produced by these intestinal bands are known as haustra, or singularly as haustrum. Have you ever rolled up a sleeping bag? You roll it up, then put the elastic bands around either end, and what happens to the middle? That's right, it bulges slightly. Same idea with the transverse colon. This is why instead of looking like a smooth tube, the transverse colon looks like a puckered, bulging tube.

Haustra, or the out-pockets of the transverse colon, function in moving feces forward.
Haustra

Functions of the Transverse Colon

The transverse colon performs several critical functions, including moving waste material forward and the absorption of key components for proper body functioning.

Moving Waste Forward

So how does a puckered tube move waste material forward? Well, the smooth-muscle in the walls of the intestines involuntarily contract propelling waste material forward. This passive movement is known as peristalsis.

But the large intestines has a second means of helping waste materials continue the journey through the digestive tract! I refer to haustral churning. When waste product has filled a single haustrum to capacity, the haustrum contracts, squishing the waste product into the next haustrum and so on and so forth, until the waste product finally reaches the rectum.

Absorbing Key Components

As the food material is moved through the entire digestive tract, the composition changes significantly. In the stomach, food is broken down into smaller products. As these products enter the small intestines they resemble a liquid, but the small intestines absorb the majority of the nutrients in the liquid. Thus by the time the food material enters the large intestines, it's significantly firmer, and is referred to as feces.

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