Embryology - Development of the face Flashcards
When does the face begin to develop in utero?
4 - 8 weeks
When does the formation of the palate occur in utero?
6 - 10 weeks
When is the first bone laid down? Where is this bone?
6 - 7 weeks
Bone of the mandible
What are pharyngeal arches/branchial arches?
Outgrowths of anterior tissue bands that lie beneath the early brain.
How many pharyngeal arches are there?
Possibly 6 but 4 main.
5 can either not develop or be very short lived.
6 under debate.
What do each of the arches contain?
Cartilaginous rod - gives rise to skeletal structures
Striated muscle
A cranial nerve
A major artery
What does the first arch give rise to?
The maxillary processes
The mandibular processes/meckel’s cartilage - mandible forms around this via intramembranous ossification.
The trigeminal nerve
Muscles of mastication
Ear
Malleus
Incus
What cranial nerve is associated with the 2nd arch?
Facial nerve
What cranial nerve is associated with the 3rd arch?
The glossopharyngeal nerve
What cranial nerve is associated with the 4th arch?
The vagus nerve
What pharyngeal arch is the common carotid artery associated with?
The 3rd arch
What pharyngeal arch is the aortic arch associated with?
The 4th arch
What does the face develop from?
5 Prominences around the stomadeum (primitive mouth)
What are the 5 prominences that the face develops from?
- Frontonasal
- Medial nasal
- Lateral nasal
Derived from the 1st pharyngeal arch:
- Maxillary
- Mandibular
What does the Frontonasal prominence gives rise to?
(Frontonasal overlays the forebrain.)
Forehead
Bridge of nose
What does the medial nasal prominence gives rise to?
Midline of the nose
Philtrum
Primary palate
What does the lateral nasal prominence gives rise to?
Alae of the nose
What does the maxillary prominence gives rise to?
Maxilla
Cheeks
Lateral upper lip
What does the mandibular prominence gives rise to?
Jaw
Lower lip
Chin (when 2 mandibular processes fuse)
Meckel’s cartilage
How is the chin formed?
From the two mandibular processes fusing
What causes a chin dimple?
When the two mandibular process partially fuse.
What forms the primary palate?
The medial nasal prominence
What forms the secondary palate/palatal shelves?
Maxillary process
How do the palatal shelves grow?
Initially grow downwards but then rotate and fuse together.
Where do the primary and secondary palate fuse together?
At the region of the incisive foramen
How are the left and right nasal cavities formed?
The medial nasal prominence grows downwards along with the frontonasal prominence and fuses with the primary and secondary palate at the midline.
What can orofacial clefts have an impact on?
Speaking
Feeding
Hearing - infection
Tooth developmental issues
What are the causes of orofacial clefts?
Multifactorial
Environmental:
Smoking
Alcohol
Viral infection
Drugs:
Vitamin A analogues
What is a cleft lip?
Failure of the maxillary prominence (palatal shelves/secondary palate) fusing to the medial nasal prominence (philtrum of lip and primary palate)
Bilateral
unilateral
Who is most affected by cleft lip? and which side does it most commonly occur on?
Males
Left
What is a cleft palate?
Two palatal shelves of the secondary palate (from the maxillary prominence) fail to fuse.
Who is most affected by cleft palate and why?
Females - have a later elevation of the palate (week 8) whereas males palate elevates at week 7
What bone(s) form from meckels cartilage?
Dorsal end = maleus and incus
Ventral end = mandible
