Development of the face, jaws & mouth Flashcards
Fronto-nasal process
Prominence in the upper facial area at the most cephalic end of the embryo.
Cephalic end
Head end of a structure such as the trilaminar embryonic disc.
Mandibular processes
Processes of first branchial arch that fuse at the middle to form mandibular arch.
Mandibular arch
lower dental arch with mandibular teeth or the 1st branchial/pharyngeal arch inferior to the stomodeum in the embryo.
Maxillary processes
Prominence from mandibular arch that grows superiorly and anteriorly on each side of the stomodeum of the emrbyo
Maxillary arch
Upper dental arch in which the maxillary teeth form.
Nasal placode
Placodes that develop into olfactory organ for the sensation of smell located in the mature nose.
Placode
Area of ectoderm found at the location of the developing special sense organs on the embryo.
In which weeks is the face established?
4th -10th week.
Mesenchyme from the frontonasal prominence arises from…
Neural crest cells (from midbrain and the forebrain)
Mesenchyme from the maxillary and mandibular prominences arises from…
Neural crest cells (from midbrain and the hindbrain)
UPDATED: week 4
Week four, swellings galore!
The primitive oral cavity is separated from the GI tract by a…
oropharyngeal membrane
(as the maxillary processes develop and enlarge ventrally and medially this starts to disintegrate)
Non-true fusion/merging
Process by which a groove between two facial processes is eliminated.
in between the groove the gap is essentially filled in by tissue proliferating upwards (in the valley) to ‘fuse’.
Where does non-true fusion occur?
Mandibular processes and maxillary processes
True fusion
Two separate processes growing towards each other, contacting and then fusing.
Does the primary palate separate the oral and nasal cavities?
No it demarcates it.
UPDATED: week 5
week five, placodes thrive!
UPDATED: week 6
week six, jaw, cheeks, duct and lips!
UPDATED: week 7
week seven, boney heaven!
UPDATED: week 8
week eight, ate
Intermaxilary segment gives rise to…
This gives rise to the philtrum, and later the primary palate (containing 4 incisor teeth).
Fairly recognisable human face by week…
10
UPDATED: week 10
week ten, fully grown men
Clinical scenario: too little fusion of the lateral portions of the maxillary and mandibular swellings.
Macrostomia (large mouth)
Clinical scenario: too much fusion of the lateral portions of the maxillary and mandibular swellings.
Microstomia (small mouth)
UPDATED: week 12
week twelve, i can’t believe those used to be palatal shelves!
UPDATED: week 16
week sixteen, we see the unseen
Contributions to the face: Frontonasal
Forehead, bridge of nose
Contributions to the face: medial nasal
Philtrum of the lip, crest and tip of nose
Contributions to the face: Lateral nasal
alae of nose
Contributions to the face: maxillary
Cheeks, lateral upper lip
Contributions to the face: mandibular
lower lip
First sign of tooth development: Primary epithelial band
Week 6
What happens in the frontonasal prominence region when there is a condensation of mesenchyme?
Mesenchymal cells start to differentiate to form chondroblasts, and the cartilage of the nose begins to form here.
Frontonasal cartilage
Supports the developments of the maxilla and will form the cartilages of the cranial base.
Two methods of bone development
- Intramembranous
- Endochondral
Intramembranous ossification
Formation of an osteoid within two dense connective tissue sheets which then replaces the connective tissue.
Mesenchymal cells differentiate into osteoblasts from osteoid.
Endochondral ossification
Bone deposit is laid down on the outside of the cartilage
Where are the primary ossification centres for the maxilla located?
It is located at the termination of the infraorbital nerve just superior to the dental lamina of the primary maxillary canine tooth, in each maxillary process.
Where are the secondary ossification centres for the maxilla located?
found at the zygomatic, orbital-nasal, nasopalatine, and intermaxillary then appear and fuse rapidly.
What week does the ossification centres for the maxilla appear?
Week 7
What generates the primary palate region?
The two intermaxillary centres generate the alveolar ridge (primary palate region).
Subsequent growth of the maxilla can be subdivided into several skeletal units
- Basal body unit
- Nasal unit
- Alveolar unit
- Pneumatic unit
Growth of maxilla: basal body unit
Develops under the infraorbital nerve and responds to the eyeball growth.
Growth of maxilla: Nasal unit
Depends on the nasal septal cartilage.
Growth of maxilla: Alveolar unit
Responds to tooth growth in the maxilla.
Growth of maxilla: Pneumatic unit
Reflects the maxillary sinus expansion.
Development of the vomer bone
Develops in inferior aspect of the nasal septum.
Intramembranous
Control of pattern formation
Retinoic acids, growth factors (BMP,FGF,Shh,Wnt & endothelins)
Controls proliferation, survival and apoptosis.
