Wall Structure – Small Intestine

by James Pickering, PhD

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    00:00 If we have look at the wall of the small intestine, then it has some similarities to the wall of the stomach.

    00:06 So it's got these muscular layers, it has a circular and longitudinal muscle layers which we can see here and also similar to the stomach, its inner lining is thrown into a series of elevations.

    00:19 But importantly these transverse folds do not disappear with distension. So the rugae in the stomach allowed the stomach to expand in size as more food passed in.

    00:35 These transverse folds known as the plicae are a permanent feature; they're not lost with distension.

    00:43 And their purpose is to increase the surface area. Increase the surface area of the small intestine allowing great opportunity for absorption to occur.

    00:57 Similar again now to the stomach, we have mucus the mucosa, sorry, the mucosa, which contains these intestinal villi.

    01:06 And these are covered themselves with microvilli.

    01:10 And these again increase the surface area. So the small intestine is long 6-7 meters long and due to this plicae, these folds, and these microvilli on top of intestinal villi, we can see that we have a very large surface area. You can see these intestinal villous here.

    01:34 Also within the wall of the small intestine, we have intestinal glands and these are found on base of those intestinal villi so we have intestinal glands; we can see some here. These are important. They contain goblet cells.

    01:50 These produce mucin which is mixed to form the mucus.

    01:55 The lines, the internal surface of the small intestine. Again important if some hydrochloric acid was to creep from the stomach into the duodenum. And it also has some stem cells. This is quite attritional environment and the food passing over can damage the cells so we have stem cells for the replenishment of the epithelial layer.

    02:21 We also, and these are only found in the duodenum have, what are known as the Brunner's glands.

    02:25 These Brunner’s glands located in the duodenum produce lots of alkaline mucus.

    02:31 This is really important as it helps to protect the duodenum from any acid that's creeping into the duodenum from the stomach.

    02:38 It also helps to inhibit the gastric acid production.

    02:43 So once the food is passed from the stomach into the duodenum, the duodenum is no longer under attack from any acid creeping in.

    02:52 So the wall structure is similar in someways that to the stomach, but it's not increasing in the surface area which is lost with distension.

    03:02 This increase in the surface area is maintained to optimize absorption.

    About the Lecture

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

    Included Quiz Questions

    1. Cecum
    2. Duodenum
    3. Jejunum
    4. Ileum
    1. Duodenum
    2. Jejunum
    3. Ileum
    4. Colon
    5. Stomach
    1. The plicae disappear with distension.
    2. The small intestine is 6–7 meters long
    3. The small intestine has villi and microvilli.
    4. Ninety percent of absorption of nutrients occurs in the small intestine.
    5. Transverse folds in the small intestine are known as plicae.
    1. It is acidic.
    2. It is very basic.
    3. It is not buffered by pancreatic secretions.
    4. It has not undergone any digestive processes.
    5. It passes through the cardiac sphincter.

    Author of lecture Wall Structure – Small Intestine

     James Pickering, PhD

    James Pickering, PhD

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