Hello. We are now gonna discuss development of the palate.
Now, if you have not yet seen the video on development of the face and the lip,
I´d like to strongly urge you to go watch that video first
so that you´re ready to see how that connects to development of the palate.
So as the nose and upper lip form, the medial nasal prominences fuse, descend,
and contact the maxillary prominences to make an unbroken upper lip.
But at the same time, they carry with them a little core of bone
and that´s actually gonna become part of the hard palate.
That region of the palate that descends
with the medial nasal prominences is called the primary palate and as the upper lip fuses,
so the primary palate fuses with palatine shelves
that are part of the maxillary prominence.
So the palatine shelves fuse with the primary palate in the front
and then, zip together to form what is called the secondary palate.
So as those palatine shelves fuse, they´re gonna zip shut from anterior to posterior
to create an unbroken hard palate at the roof of our mouth
and at the floor of our nasal cavities.
The point of juncture between the primary palate
and the two secondary palates or the palatine shelves
are going to be marked by the incisive frame
and this is a little hole in the bone where blood vessels and nerves are moving
between the oral cavity and nasal cavity.
If everything goes to plan, we have a completely fused hard palate
with a soft palate extending off the back of it
and the uvula is going to be right on the midline
and extending down towards the throat to alert us
to when substances are in our mouth and keep our body updated as we swallow
and also, to seal off the nasal cavities as we swallow
so we don´t have food moving up into our nasal area.
If we take a coronal view through the head,
we can see that the nasal septum is growing down in the nasal cavity.
Initially, there´s one fused nasal chamber
but as development proceeds, the septum grows down.
The tongue is going to come to a lower position in the mouth
and that´s going to allow the two palatine shelves to move upward,
fuse with each other to create the secondary palate.
And then, fuse with the nasal septum.
So when all is said and done,
we have a single oral cavity and two separate nasal cavities.
Now, if we have a cleft lip, there´s a very likely chance
that we´re going to come up with a palatine defect as well
because the philtrum of the upper lip
is also contributing the primary palate to the hard palate.
So if you have a unilateral cleft lip,
it´s not uncommon to find a cleft running between the side of the primary palate
and the secondary palate on that same side and if you have a bilateral cleft lip,
you can indeed have complete separation of the primary palate
from the secondary palate.
One interesting thing that happens in this regard
is that the primary palate is also where the incisor teeth are going to develop
and you can have two completely free incisor teeth stuck
on this little kind of hanging bit of tissue extending down
from the philtrum with the rest of the teeth in the jaw and in the maxilla as we´d expect.
Now, if that doesn´t happen, we can also have a cleft palate occur
if the two palatine shelves don´t come together in the way we´d expect
because it tends to seal up from anterior to posterior,
it´s more common to find these palatine clefts
as you go further posterior onto the hard palate and extending onto the soft palate.
And the most innocent version of this is a bifid uvula
where the uvula instead of fusing into a single structure is split into two.
Usually, not problematic.
Just something that you may notice as you´re examining a patient
and doing the oral exam.
Now, in some instances,
we can have failure of almost every one of these structures to fuse
and on the case of this child,
we can see that the medial nasal prominences forming the philtrum
have not fused with the maxillary prominences on either side of the upper lip
but likewise, we have failure of the primary palate, secondary palate,
and nasal septum to all fuse.
So let´s take a look at the inside upper portion of this person´s mouth
and see if we can break that down.
At the very top of the image, that little bulge at the edge of the image
is the philtrum derived from the medial nasal prominences.
A little bit further down is a bilobed appearing primary palate.
That´s where the incisor teeth will develop
and we´d expect it to fuse with the palatine shelves
which are located just a little bit down and on either side of the mouth.
Extending right down the midline of the image is a little red streak.
That´s actually the nasal septum
which has failed to fuse with the palatine shelves on the left and the right.
So in this child´s instance, we´re going to have a combined cavity of the oral cavity,
the right nasal cavity, and the left nasal cavity.
Now, the good news is that these malformations
can readily be corrected surgically.
So as long as someone has access to care or in certain countries,
charitable organizations that are able to come in
and do these surgeries free of charge, they can be corrected pretty readily.
But unless they´re corrected, it can be very difficult for these infants to feed
because the cleft lips and cleft palates
make it impossible for them to make a tight seal
while they´re feeding and suckle effectively.
So, in these infants´ case you may have to assist them by gravity feeding
and allowing the milk to move into their mouth
without them being able to completely form a vacuum and pull it in on their own.
Thank you very much and I´ll see you for our next talk.