Embryology of Face, Skull, and Palate Flashcards
What tissues is the skull derived from embryologically?
Anterior portion is derived form neural crest cells
Posterior portion is derived from paraxial mesoderm
What are fontanelles and what is significant about them?
Soft spots between the bones of the skull. They allow for post-natal growth of the skull and flexibility of the calvaria during birthing. The sutures remain flexible throughout childhood.
What is Craniostosis? (cause and manifestations)
Caused by early fusion of the cranial sutures
- Scaphocephaly - sagittal suture fuses early causing an elongated skull
- Brachyocephaly - coronal suture fuses early causing a widened skull
The face is formed from 3 prominences. What are they called and what structures do they give rise to?
Frontonasal prominence - forehead, bridge of nose, nasal septum, apex of nose (medial nasal prominence), philum of lip (medial nasal prominence), ala of nose (lateral nasal prominence)
Maxillary prominence - upper cheek and lateral upper lips
Mandibular prominence - lower cheek, lower lip, chin, and external part of ear
How do the nasal placodes form the nose and lips?
Nasal placodes will invaginate to create the nasal pits. The mesenchyme surrounding the nasal pits will then proliferate to form medial and lateral nasal prominences. Medial nasal prominences will fuse and form the intermaxillary segment, which fuses with the maxillary prominences to form the upper lip.
How does the nasolacrimal duct form?
The fusion of the lateral nasal prominences with the maxillary prominences causes the formation of a nasolacrimal groove
How does the nasal cavity develop?
Nasal pits extend dorsally forming nasal sacs separated from the oral cavity by the oronasal membrane. This membrane will degenerate and be replaced by the palate.
Two neural structures will derive themselves from the superior portion of the nasal sac
Olfactory epithelium and CN I
What is the incisive canal a landmark of?
The fusion of primary and secondary palates
How does the palate form?
The intermaxillary segment will give rise to the primary palate and fuse with the lateral palatine shelves and nasal septum. Lateral palatine shelves (maxillary prominences) begin by projecting inferomedially at the level of the tongue and move supriorly to fuse with each other, the primary palate, and nasal septum.
Anterior cleft palate (Cause and manifestation)
Failure of the maxillary prominences to fuse with the medial nasal prominence
A complete cleft extending through the lip, the alveolar maxilla, and incisive foramen separating the primary and secondary palates
Posterior cleft palate (Cause and manifestation)
Lack of fusion of the lateral nasal prominences
Cleft palate and/or uvula
Oblique facial cleft (Cause and manifestation)
Failure of the lateral nasal prominence to fuse with the maxillary prominence
Cleft running from mouth towards the eye. Nasolacrimal duct does not incorporate into the face.
