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Review of the Folding of the Embryo – Liver, Gallbladder and Pancreas Development

by John McLachlan, PhD
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    00:01 Hello, and welcome to this lecture on the development of the gut, the second of two lectures on gut development. In this one, we’ll be looking at some structures which grow from the gut or associated closely with it. So we’ll be looking at the liver, the gall bladder, the pancreas, the spleen and we’ll also mention some abnormalities and variations that can occur around your development. To understand the gut, of course, we have to return to folding of the embryo. So in this image, we see the amniotic cavity in the upper part of the image, and the yolk sac down below that. As the embryo sweeps round, rises up into the amniotic cavity, so it does at the fore and hind end of the embryo to begin to create the fore and hindgut. The midgut remains open to the yolk sac.

    00:53 Here, we’ve emphasized these in green. So we can see the formation of the fore and hindgut as the folding of the embryo takes place. As the embryo is developing into a C-shape, so the gut also will begin to develop a curve running from the mouth down to the anus.

    01:11 At these early stages, both the mouth and the anus were closed by membranes, and these membranes will later disappear. From the foregut, developed the lungs, and that is explored in another lecture But in this case, we’re looking particularly at the liver. So this is going to develop as a bud from the foregut. Let’s look at the relationships between the tissues in transverse section, because this will be important to understanding the relationship of the liver with the mesoderm. Here in this transverse section, we see the amniotic cavity above and the yolk sac below. As the amniotic cavity sweeps round the body of the embryo, so it begins to pinch off part of the yolk sac, lined of course with endoderm.

    01:56 It’s also important to understand this in transverse view because the relationship of the gut and the liver with the mesoderm is particularly important. So, in this image, we can see, first of all, transverse cross-section with the amniotic cavity above and the yolk sac below.

    02:12 As the amniotic cavity sweeps round, it begins to create the definitive intraembryonic coelom, and the gut is pinched off from the yolk sac and comes to lie suspended from a dorsal mesentery and attached by a ventral mesentery. The yolk sac itself was reduced to a stalk, and this is in the midgut region of the embryo. In the image marked D, we can now see the gut suspended in its dorsal mesentery above and attached by its ventral mesentery to the anterior wall of the abdomen on the inside. It is surrounded by the intraembryonic coelom, which will later be the abdominal cavity. It is from the gut that the liver will begin to grow, and it grows eventually as down the way from the original gut.


    About the Lecture

    The lecture Review of the Folding of the Embryo – Liver, Gallbladder and Pancreas Development by John McLachlan, PhD is from the course System-Specific Embryology with John McLachlan.


    Author of lecture Review of the Folding of the Embryo – Liver, Gallbladder and Pancreas Development

     John McLachlan, PhD

    John McLachlan, PhD


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