large Intestine: Structure/Function

large Intestine: Structure/Function


This lesson will discuss the structure and function of the large intestine and examine its role in digestion.

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Large Intestine

Source: Video and Images Created by Amanda Soderlind

Video Transcription

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Welcome to this lesson.

Today we are going to be taking a look at the structure and the function of the large intestine, and its role in digestion.

Basically, the large intestine is a part of the digestive system whose role is to absorb remaining nutrients and water. So as food moves from the small intestine into the large intestine, any remaining nutrients that have not already been absorbed will be absorbed in the large intestine. And water is also absorbed here, as well. And it also rids the body of any remaining waste products.

We're going to take a look at this diagram right here, and basically just label the different structures associated with the large intestine.

If we take a look, we're going to start right here. And this is actually the ilium of the small intestine.

This is the location where the small intestine connects with the large intestine. So we have the ilium of the small intestine that connects here to the large intestine.

Down here on the bottom of this part of the intestine, we have this little appendage kind of sticking off here. And this is actually our appendix.

Our appendix is a part of the large intestine that stores B and T cells, and the purpose for this is to attack and kill any parasites that are in the food at this point, as it moves through the large intestine. It's not absolutely necessary to have our appendix. You may have known somebody who's had their appendix removed before. You can survive without your appendix, so it's not necessary to have it, but it's just something that's there to kill any parasites that are still in food as it passes through. But generally at this point, most parasites, if they were in your food, have already been taken care of by the stomach acid in your stomach and so on.

OK, so moving on. Actually our large intestine is broken down into two sections. We have the colon and the rectum. So those are the two sections of the large intestine.

The colon is then broken down into three subsections.

The first subsection is called the ascending colon. We call it the ascending colon because it's going up, we're ascending upwards.

The next part of the colon is called the transverse colon. These names makes sense because transverse means across.

Then the next part is the descending colon, which is the part of the colon that is going down.

So those parts of the colon, it's easy to remember by their names which part is which.

Then the next part is the rectum. And then we have the anus.

So as food moves through the small intestine, it'll move towards the large intestine, to the ascending colon. Muscle contraction stimulated by hormones will help to move the material through the large intestine. Water and any remaining nutrients will be absorbed, until finally we get down towards the rectum, where we have waste build up.

And then waste is secreted through the anus. Basically, waste is unabsorbed water, undigested matter, and bacteria that the body can't use.

As water is absorbed throughout this process, as it moves through the large intestine, it basically concentrates the waste. And then anything that wasn't used, as I mentioned, unabsorbed water, undigested matter, bacteria are then passed.

This lesson has been an overview on the structure and function of the large intestine.

  • Large Intestine/Colon

    The last major tubular organ of the alimentary canal, it forms a frame around the small intestine. The colon is responsible for absorbing water and electrolytes and converting the bolus into fecal matter.

  • Rectum

    The digestive system analog to the urinary bladder, the rectum stores fecal matter until it’s time to excrete it from the body.

  • Appendix

    A vestigial organ that is located on the lower right side of the colon, the appendix contains lymph nodules called Peyer’s patches. Sometimes the appendix becomes inflamed and ruptures during a condition called appendicitis.

  • Anus

    The opening of the rectum, the anus is the last part of the alimentary canal that fecal matter escapes through.