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Large Intestine

Large Intestine

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

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Tutorial

What's Covered

Welcome to this lesson. Today you are going to be taking a look at the structure and the function of the large intestine, and its role in digestion. Specifically, you will learn about:

  1. Large Intestine Function
  2. Large Intestine Structure

1. Large Intestine Function

The large intestine is the part of the digestive system whose role is to absorb remaining nutrients and water.

Term to Know

    • 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.

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. Any water and undigested materials that remain within the large intestine will be removed as waste i.e. fecal matter.


2. Large Intestine Structure

As you go through the structure of the large intestine, refer to the diagram below for a visual representation.

The ilium of the small intestine is the part where the small intestine connects with the large intestine. Also, down at the bottom of the large intestine near where it meets the small intestine, there is a little appendage protruding out known as the appendix.

Term to Know

    • 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.

The appendix is a part of the large intestine that stores B and T cells within lymph nodules. Its purpose is to attack and kill any parasites that are in the food at this point as it reaches this part of the large intestine.

Did You Know

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; it's just there to kill any parasites that are still in food as it passes through. Generally at this point, most parasites, have already been taken care of by stomach acid.

The large intestine is broken down into two sections: the colon and the rectum.

Term to Know

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

The large intestine is then broken down into three subsections. The first subsection is called the ascending colon, because it's going up or ascending upwards. The next part of the colon is called the transverse colon, because transverse means across. Then the next part is the descending colon, which is the part of the colon that is going down. After these three structures you'll find the rectum and the anus where waste is stored and removed.

Term to Know

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

As food moves through the small intestine it moves toward the ascending colon. Muscle contractions stimulated by hormones will help to move the material through the large intestine. Water and any remaining nutrients will be absorbed, until finally you get down towards the rectum, where you have waste build up.

Waste is secreted through the anus and is nothing more than unabsorbed water, undigested matter, and bacteria that the body can't use. As water is absorbed throughout this process the large intestine concentrates the waste. Anything that wasn't used (unabsorbed water, undigested matter, bacteria) are then passed.

Summary

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

Keep up the learning and have a great day!

Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND​

TERMS TO KNOW
  • Anus

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

  • 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.

  • Rectum

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

  • 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.