Development of the Face – Primary and Secondary Palate Development

by John McLachlan, PhD

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    00:01 Hello, and welcome to this lecture on the development of the primary and secondary palate, and the abnormalities that can arise during this process. What we’re going to do is to review briefly the development of the face, and then we’ll describe the development of the primary and the secondary palate. This is a process which can go wrong. So we’ll also look at the frequency, the causes, and the consequences of cleft lip and palate.

    00:26 While we’re in this region, we’ll also describe some other abnormalities of the head and neck. It may, in fact, be useful to review the lecture on the pharyngeal arches as part of the preparation for understanding this particular lecture. Something which is hard to show in still pictures is the fact that the face is growing in relative terms throughout the whole of the process of face development. So in order to help make this clear, we’ve prepared a video which is developed with funding from the Welcome foundation and in collaboration with Helen Storey. So this is the video looking in the face of an early human embryo.

    01:05 What we’re going to do is to focus on the relative growth and changes that take place during this process. In particular, we’ll be interested in the midline of the face just above the mouth where the two nasal processes are coming together to form a central segment, which we will see is called the intermaxillary segment. Of course development is a continuous process, and it extends through the development of the baby into infancy and childhood, and finally on into later old age.

    01:51 So, let’s look at some still images showing these processes.

    01:55 The frontonasal prominence is projecting towards you out of the plane of the screen and on either side are pits which represent the developing nostrils. At these early stages, the eyes are still round to the side and they will not become visible until later in the course of development. The nasal pit has begun to deepen and developed clearly marked walls on either side. The maxillary and mandibular processes are growing towards each other in the midline, and we’ll be interested in the part lying between the two maxillary processes on either side. Here, we see a later stage. The walls surrounding the developing nostrils are still not complete. And the fact that they open towards the mouth, as we will see, is significant in terms of cleft lip development. So we’re noting at this point. Also a central process, the maxillary, the intermaxillary process in the midline, and that is also going to be significant later on. The maxillary process is still separated by grooves from the nasal walls and also from the mandible, and gradually, it will begin to fuse with these structures in normal development. The ears are relatively low down on the body, and they will shift their relative position during the course of development.

    03:16 The eyes are now becoming visible as they move towards their final position on the front of the face.

    03:24 Remember, as the illustration in the movie showed that this is a moving process, the whole embryo is growing, although the diagrams do not fully represent this. At a later stage, we can identify the ears, although they’re still in a position lower down on the neck and the mouth is beginning to close together as the eyes develop eyelids round towards the front. The nasal part or the frontonasal prominence is now beginning to fuse with the maxillary process in normal development, and the mouth becomes less wide. The gaps which connect the various processes to the nasal parts to the intermaxillary segment would normally begin to fuse together. So here we can see maxillary process fusing with mandibular processes to form the normal mouth.

    About the Lecture

    The lecture Development of the Face – Primary and Secondary Palate Development by John McLachlan, PhD is from the course System-Specific Embryology with John McLachlan.

    Author of lecture Development of the Face – Primary and Secondary Palate Development

     John McLachlan, PhD

    John McLachlan, PhD

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