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Wall Structure – Large Intestine

by James Pickering, PhD
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    00:01 If we look at the wall structure of the large intestine then we can see we have this band of longitudinal muscle. But again importantly it really is just associated with taenia we don't have that complete band of longitudinal muscle. Remember those three of those taeina coli. But we also have the circular layer which is consistent around them.

    00:22 If we look at the structure of the large intestine, it's wall, we see that it has a larger diameter than the small intestine. But the wall is actually thinner the wall is actually a lot thinner than the small intestine. There is an absence of villi so we don't have this big surface area which is enhanced by the villi in the small intestine. This is indicative of the fact that it is not actually been that active in absorption. It is just absorbing some water and vitamin. Its main priority is to store faeces until defecation and that's why we have these distinctive intestinal glands which are located in the wall of the large intestine. And within these glands there is an abundance of goblet cells and these produces lots of, lots of, lots of and lots of mucus. Because the water is being drown out from the faeces, they can actually become quite dehydrated dry. So we need to have some lubrication via this mucus to allow the faeces to pass through the large intestine and ultimately be removed.

    01:33 This is a picture of an actual piece of large intestine which has a series of little pouches and these are unusual. Well we can see in this diagram is we got a taenia coli here. And we can actually make out some little pouches which we can see here. Some little bulging pouches and these are called diverticuli. These little pouches are not normally occurring in the large intestine. But they are bulging out from the wall of the large intestine. Now diverticulosis is a series of these out-pouchings along the wall of colon and it usually found in the sigmoid colon.

    02:15 The result of changes in pressure with defaecation now what the likely cause of them is the lack of fiber within your diet. If you did not have a high level of fiber within your diet then a lot of the water from the faeces is absorbed If you have some fiber in your diet, which isn't really digested, that's going to hold onto the water and make your faeces softer. Because you know you have a high level of water in your faeces that can be easily removed; because, its quite soft and the flow can be relatively smooth. If there is a lack of fiber, a lot of the water is removed which makes the stools hard. For these to be defaecated, for these to be removed, you have to increase intra-abdominal pressure to such an extent that you are physically forcing the faeces away, they're not allowed to just glide away. This can change the pressure within the large intestine and resulting in these little out-pouchings occurring. If we have these outpouchings, and then they become occluded, they can lead to infections and inflammations and with this inflammation, you can have diverticulitis where they become inflamed.

    03:28 If they end up bleeding, they can be quite painful and then you can develop having blood in your stools. So diverticulosis leading to the diverticulitis can be quite serious condition.


    About the Lecture

    The lecture Wall Structure – Large Intestine by James Pickering, PhD is from the course Abdomen.


    Included Quiz Questions

    1. The walls are thick as compared to the small intestine
    2. The walls are thin as compared to the small intestine
    3. There is an absence of villi and microvilli
    4. Its function is to store feces
    5. It helps in the absorption of water and vitamins
    1. Goblet cells
    2. Parietal cells
    3. Chief cells
    4. Enterochromaffin-like cells
    5. Alpha cells

    Author of lecture Wall Structure – Large Intestine

     James Pickering, PhD

    James Pickering, PhD


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