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.
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.
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.
So, let’s look at
some still images showing these processes.
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.
The eyes are now becoming visible as they move towards
their final position on the front of the face.
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.