Jejunum and Ileum – Small Intestine

by James Pickering, PhD

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    00:00 If we now look at the jejunum and the ileum, well these are very similar. And many students ask well where exactly does the jejunum finish and the ileum begin? And that's quite a difficult question.

    00:15 Because as a very gradual change there is a clear demarcation between duodenum and jejunum and that's a sling like piece of muscle or ligament.

    00:26 And that helps to separate the duodenum and the jejunum helps to maintain the duodenojejunal flexure allowing chyme to pass through the duodenum into the jejunum.

    00:36 But it’s very difficult to see a noticeable difference in the transition from jejunum to ileum. But what you can do you can look at the very beginning at the jejunum and look at the very end of the ileum and there you notice some differences.

    00:51 So here we have from proximal to distal. So we have by the duodenum and by the large intestine.

    00:58 We have the jejunum and then we have a becoming the ileum.

    01:03 So we can see that with the jejunum, we still have these circular folds.

    01:08 But as we progress towards the distal ileum we see these circular folds have died down. There is not as much fat around the jejunum; there is slightly more fat around the proximal ileum and more fat still around the distal ileum.

    01:25 The vasculature, the blood supply to the jejunum is greater than the ileum.

    01:30 So the wall of the jejunum is somewhat pinker than the proximal or the distal ileum. And there is a whole series of other differences which really have a transition from the jejunum through to the distal ileum and I have detailed some here. So we can see the color of the distal ileum is quite...

    01:50 is quite dark red and as it progresses to the jejunum it comes pinker.

    01:56 The diameter is greater in the jejunum that is in the distal ileum I mentioned that at the beginning.

    02:01 The actual thickness of the wall is greater in the jejunum compared to the distal ileum.

    02:08 The blood supply is greater in the jejunum indicating there is a higher level of absorption that’s occurring in this region. The fat in the mesentery - there is more as you progress down into the the distal ileum. It's very sparse in the jejunum.

    02:23 Circular folds, there is lots of them in the jejunum.

    02:25 There is few in the distal ileum; it’s a lot flatter.

    02:29 And lymphoid nodules - that's few in the jejunum, but they increase in number forming this aggregates in the distal ileum.

    02:38 So we can see that it’s very difficult to actually pinpoint this specific region. Especially halfway this kind of proximal ileum region and say yes this is definitely jejunum this is definitely ileum.

    02:52 But there is a transition from the duodenal- -jejunal junction to where the ileum merges with the large intestine.

    03:00 There is a transition which is indicating in these descriptions.

    About the Lecture

    The lecture Jejunum and Ileum – Small Intestine by James Pickering, PhD is from the course Abdomen.

    Included Quiz Questions

    1. The jejunum is greater in diameter.
    2. The jejunum is paler (less red) in color.
    3. The jejunum has higher quantities of fat in its associated mesentery.
    4. The jejunum has a reduced blood supply.
    1. The jejunum has fewer circular folds than the ileum.
    2. The jejunum is wider than the ileum.
    3. The jejunum is thicker than the ileum.
    4. The jejunum has fewer lymphoid nodules than the ileum.

    Author of lecture Jejunum and Ileum – Small Intestine

     James Pickering, PhD

    James Pickering, PhD

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