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Transverse View – Lung Development

by John McLachlan, PhD
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    00:00 surfactant. Now let’s look at the development of the lungs as seen in a transverse section across the axis of the embryo. In this image, we can see the neural tube at the top, and we can see the gut suspended, surrounded by mesoderm with the heart hanging in the developing pleuropericardial cavity. And off to the side of the gut, we can see the lung buds.

    00:27 So this is a very early stage when only two lung buds are present. And in this view, they are cut in section. A little later still, we can see that lung buds are distinctly separate and surrounded by their mesoderm. Now looking at the cavity, we can see a little piece of the heart, but the most striking thing is two-folds which are growing in from either side.

    00:51 These folds are known as the pleuropericardial folds, and these are dividing the primitive cavity which is both pleural and pericardial in nature into the definitive pleural and pericardial cavities. A little later still, we can see that the pleuropericardial folds have met in the midline, and the pleural cavity and the pericardial cavity are now completely separate. What will happen now is that the lungs begin to expand around with their pleural cavities until they come to encompass the heart. So when you look at the front view of an adult, only a small part of the heart would be directly accessible, otherwise, the lungs would be covering over where the heart actually lies. Now, we’ve followed through the normal process of development, but there are significant events associated with the birth itself. While still in the uterus, the baby is showing breathing movements, and fluid is moving in and out the mouth and lungs. This fluid is a combination of amniotic fluid and fluid secreted by the lungs themselves. When the baby is born, this fluid will drain from the lungs, and it may have to be assisted by suction to allow that to take place completely.

    02:10 At that point as the baby breathes in, the surfactant would normally be present in sufficient amounts to keep the lungs inflated and to permit respiration to take place.

    02:21 If there are inadequate amounts of surfactant, then there’s a risk that the lung might collapse at the stage when the fluid leaves the lungs. If there was any fluid left remaining in the lungs that’s not been drained out, it’s normally reabsorbed by the capillaries.


    About the Lecture

    The lecture Transverse View – Lung Development by John McLachlan, PhD is from the course System-Specific Embryology with John McLachlan.


    Author of lecture Transverse View – Lung Development

     John McLachlan, PhD

    John McLachlan, PhD


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