10 - Head and Neck Development 2 Flashcards
(39 cards)
What are the growth centers of the face? What do they surround?
Frontonasal prominence, maxillary prominence, and the mandibular prominence.
They surround the stomadeum, the primordial mouth.
What is the difference between fusion and merging?
Fusion: two free structures come together, oppose each other, and the epithelium between them degenerates and the underlying mesenchyme comes together.
Merging: accumulation of mesenchyme underneath adjacent prominences.
Where are the lateral and medial nasal prominences located? What do these surround?
Within the frontonasal prominence.
Surrounds the nasal placode, which becomes the floor of the nasal pit.
What forms the nasolacrimal duct?
The maxillary prominence fusing with the lateral nasal prominence and frontonasal prominence.
What do the medial nasal prominences form?
The intermaxillary segment:
- middle part of the upper lip
- incisor bridge of the maxilla
- primary palate
The fusion of the maxillary prominence and the medial nasal prominence completes the formation of what?
The upper lip.
As a result of the fusion of the maxillary prominence and the medial nasal prominence, the primitive nasal cavity is now isolated from what?
The oral cavity and the nasopharynx.
The maxillary prominence merges with the mandibular prominence to form what?
The cheek and narrows the opening of the mouth.
The lower jaw is now complete.
How does is the communication between the nasal cavity and the pharynx established?
The lateral and medial prominences expand and form a nasal pit.
The oronasal membrane between the nasal cavity and the oral cavity will stretch out and rupture, causing a communication between the nasal cavity and the developing nasopharynx called the choana.
When the choana are formed, what structure is now present?
The soft palate, a boney shelf that separates the oral and nasal cavity.
What is choanal atresia?
The absence of the nasal choanae (a hole not forming).
What type of atresia can cause respiratory distress in newborn infants?
Bilateral choanal atresia, because newborns are obligate nasal breathers.
What is responsible for the depth and height of the nasal cavity and kepts the orbit separated at a proper distance
Ethmoid bone.
Describe the growth of the mid-face that occurs during weeks 5-9?
Constant and lateral.
Arch 1 grows faster than the others. Facial muscles (arch 2) grow over those derived from arch 1.
Eyes move toward the midline and ears move superio-dorsally.
What important switch happens between week 7 and 8?
The switch of blood supply from the stapedial artery to the external carotid artery.
What is the ratio of size of the cranium:face in newborns and adults?
Newborns: 8:1
Adult: 3:1
What are the two parts of the human palate?
The primary part, which is a small structure in adults, and the secondary part.
In the clinic, only the secondary palate is considered when the palate is discussed.
How do the palatine shelves fuse? What helps them do this?
They are directed downward and flip up to fuse together with the primary palate to form the definitive palate.
Glycosaminoglycans allow the palatine shelves to expand and fuse (shelf force).
What must the tongue do during palate formation?
Move inferiorly, which is caused by the expansion of the lower jaw.
What must remain constant during the fusion of the palatine shelves?
The width of the oral cavity.
What is the critical period for facial development?
3-9 weeks.
Failure of fusion between prominences can result in _____ defects.
Cleft defects, such as oro-orbital or oro-auricular clefts.
These can be fleshy or bone and can be unilateral or bilateral.
What are factors that contribute to palate clefting?
Insufficient growth, interference with fusion, re-rupture of a fusion.
What are three syndromes associated with the first arch?
- Mandibulofacial dysostosis (treacher collins syndrome)
- Mandibular hypoplasia (pierre Robin sequence)
- Maxillary hypoplasia (crouzan syndrome)
