Embryology of Face, Mouth and Palate Flashcards
What is the stomodeum?
primitive mouth
What are prominences?
5 neural crest populations around the stomodeum
Name the 5 facial primordial prominences?
Single frontal nasal prominence
Paired maxillary prominences
Paired mandibular prominences
What does the dingle frontonasal prominence form?
the forehead & most of nose, optic vesicles > eyes
- derived from mesenchymal cells from forebrain & midbrain neural crest cells
What does the maxillary prominence form?
upper cheek regions & upper lip
- from neural crest-derived mesenchyme (1st pair of pharyngeal arches)
What does the mandibular prominences form?
chin, lower lip, lower cheek
- from neural crest-derived mesenchyme (1st pair of pharyngeal arches)
Early cranial mesoderm consists mainly of?
- paraxial mesoderm
- prechordal mesoderm
- lateral mesoderm
Paraxial mesoderm forms?
connective tissues, muscles & skeletal elements of cranial region
Prechordal mesoderm form?
contributes to extraocular muscles
- located in the midline, rostral to the tip of notochord
Lateral mesoderm forms?
Contributes to endothelial and smooth muscle cells
When do the nasal cavities begin to develop?
End of 4th week
What are nasal placodes?
thickenings of surface ectoderm
- primordia of nasal pits & nasal epithelium
What are the nasal pits?
Primordial of nostrils and nasal cavities
- proliferation of mesenchyme in maxillary prominence causes them to grow towards each other
What separates the maxillary processes and Lateral nasal prominences?
Nasolacrimal groove
> Epithelial cord canalizes in nasolacrimal groove to form nasolacrimal duct - carries tears from lacrimal sac to nasal
Describe nasal placodes and how they become nasal pits?
thickenings of surface ectoderm nasal pits > deepening > nasal sacs
What are oronasal membranes and what happens to them?
Oronasal membrane separates the oral cavity from the nasal sacs
> Membrane ruptures (end of 6th wk)
- primordial chonae (opening betwn nasal cavity and nasopharynx)
Describe the development of the olfactory system?
- Ectodermal epithelium in the roof of each nasal cavity > specialized > olfactory epithelium
- Some epithelial cells differentiate into olfactory receptor cells (neurons) whose axons become olfactory nerves and grow into olfactory bulbs of the brain
Describe the development of paranasal sinuses?
- From outgrowths of nasal cavity walls > pneumatic (air-filled) extensions of the nasal cavities in adjacent bones
- Original openings of the outgrowths persist as the orifices of the adult sinuses
1. Frontal sinuses
2. Sphenoidal or maxillary sinuses
3. Ethmoidal sinuses
Note: Paranasal sinuses develop in late fetal life & after birth
Describe the development of the face at the end of the 5th week?
primordia of auricles (external part of ears) have begun to develop
> Six auricular hillocks (3 mesenchymal swellings on each side) form around 1st pharyngeal pouch
- auricle, external acoustic meatus
Note: initially the external ears are located in the neck region, but as the mandible develops they are located on the side of the head
Describe the development of the face between the 7th and 10th week?
Medial nasal prominences merge with each other and with maxillary & lateral nasal prominences to give:
1. Middle part (philtrum) of the upper lip
2. premaxillary part of maxilla & gingiva (gum)
3. primary palate
The first pharyngeal arch develops into?
Muscles of mastication (V)
The second pharyngeal arch develops into?
Muscles of facial expression (VII)
What is the labiogingival lamina?
thickening of ectoderm
> lips, gum, lingual frenulum
Describe how the face changes during its development?
- Early fetal period: Flat nose and underdeveloped mandible
- Enlarging brain: Prominent forehead, medial movement of eyes & external ears rise
When does palatogenesis take place?
6th - 12th week
Describe the development of the primary palate?
- Median palatine process begins to develop from deep intermaxillary segment of maxilla
-Primary palate forms the premaxillary part of the maxilla - Represents only a small part of adult hard palate (anterior to the incisive foramen that lodges the incisor teeth)
Describe the development of the secondary palate?
- Bone develops in primary palate forming the premaxillary part of the maxilla which lodges between the incisor teeth
- Bone extends from the maxillae and palatine bones into palatine processes to form the hard palate
- Posterior aspects do not ossify
- Extend posteriorly to form soft palate & uvula
- Palatine raphe permanently indicates the line of fusion of the lateral palatine processes
- Small nasopalatine canal persists
between premaxilla and palatine
processes as incisive fossa (opening for
incisive canal)
Describe palate anomalies?
Cleft palate - associated with cleft lip
> failure of mesenchymal masses in the lateral processes to fuse
- neural crest cells implicated
1. Anterior cleft anomalies
2. Posterior cleft anomalies
3. Unilateral clefts
4. Bilateral clefts
