Surface Anatomy – Small Intestine

by James Pickering, PhD

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    00:01 So we start off by looking at the surface anatomy of the small intestine and where exactly it is positioned within the abdomen.

    00:08 And then we going to look at the gross anatomy of it.

    00:11 So look at the three parts: Duodenum, Jejunum and Ileum.

    00:15 And look at the location of these areas. The relations they have to other organs within the abdomen. We will look at the wall structure and then, like of the stomach, we will look at its neurovascular supply.

    00:29 So small intestine is really important. It’s the main site for chemical digestion and then absorption. So receives bile from the liver And this helps to break down (emulsify) the fats.

    00:44 And it also receives digestive enzymes from the pancreas.

    00:48 So it's intimately associated, as we will see, with these organs.

    00:53 The chyme can then now be absorbed through the walls of the epithelium of the small intestine and then pass into the blood stream.

    01:02 So the small intestine finishes off this digestion and then allows absorption to occur.

    01:11 So we start, how we usually start with these lectures, and we will look briefly at the surface anatomy, the position of them as it's been put on to the torso. So here we can see, just in this one, we just have the initial part of the small intestine, the duodenum this "C" shaped structure. And this will be continuous with the "J" shaped stomach that we saw in the previous lecture. So we have got the stomach, we have got the oesophagus which is coming down in this direction. And we can see this "C" shaped duodenum, that's the first part of the small intestine. And we can't actually see that part of the small intestine that clearly on this diagram. Again we can see the oesophagus nicely passing down through the thorax entering the abdomen through the diaphragm and then being continuous with the dilated sac of the stomach.

    02:04 The stomach is then continuous with the small intestine, initially the duodenum which is aligned posterior to what we know as transverse colon and also it passes the liver.

    02:16 The duodenum is what’s known as retroperitoneal. We will come back to this term later on. But it means it aligns behind the peritoneum which as we will see is the membranous sac that is within the abdominal cavity.

    02:32 The duodenum is then continuous with the small intestine. And here we can see the coils of jejunum and the coils of ileum that forms the small intestine.

    02:42 And these are incredibly long; this tube is passing through the gastrointestinal tract And it passes really from this upper left quadrant down in this direction towards the lower right quadrant where is then continuous with the large intestine.

    02:58 And it does this by these coils of jejunum and ileum as we'll see.

    03:04 So some key facts with regards to the small intestine.

    03:07 About 90% of the ingested nutrients are absorbed by the small intestine so it carries out the majority of the absorption.

    03:16 It’s fairly long, six to seven meters in length.

    03:20 And as it passes from the stomach to the large intestine it decreases in diameter from around about 4cm in the stomach to about 2cm at the junction of the large intestine.

    03:35 It’s a big, long, sprawling part of the GI tract and it’s found within 6 of those 9 abdominal regions.

    03:44 It’s found in 6 of the 9 and it's not found in the hypochondria, the right and the left hypochondriac regions and also the epigastrium. So it’s found in the lower 6.

    03:56 It's divided, as I have mentioned before, into three subdivisions and from proximal to distal so from the stomach to the large intestine we have the duodenum, the jejunum and the ileum.

    04:10 The duodenum is important as it receives digestive secretions from both the liver, bile; and the pancreas, the pancreatic juice like amylase to aid digestion, to help break down the ingested food so it can be absorbed.

    About the Lecture

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

    Included Quiz Questions

    1. Duodenum
    2. Jejunum
    3. Ileum
    4. Transverse colon
    5. Appendix
    1. Duodenum
    2. Stomach
    3. Jejunum
    4. Ileum
    5. Colon

    Author of lecture Surface Anatomy – Small Intestine

     James Pickering, PhD

    James Pickering, PhD

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