2. Ontogenetic development of the jaws, oral cavity floor and tongue. Formation of lips and palate. Jaws ratios. Factors influencing the development

when is maxillofacial region formed?

4th and 7th week

where does maxillofacial region develop primarily?

first pharyngeal arch and neural crest cells

how are maxilla, mandible and oral cavity formed?

through migration and differentiation of neural crest cells

Mandible

• develops from mandibular process of 1st pharyngeal arch and Meckel’s cartilage

• 2 mandibular processes fuse at midline 

• grows forwards and out

• Ossification begins in 7th week via intramembranous ossification 

what does mandible develop from?

• develops from mandibular process of 1st pharyngeal arch and Meckel’s cartilage

when does ossification of mandible begin and via what?

• Ossification begins in 7th week via intramembranous ossification 

Maxilla

• Develops directly through intramembranous ossification within the mesenchyme derived from the first pharyngeal arch 

• Grows forward and down 

where and how is maxilla formed?

• Develops directly through intramembranous ossification within the mesenchyme derived from the first pharyngeal arch 

in which direction does mandible grow?

• forward and out 

In which direction does maxilla grow?

forward and down

Tongue

• anterior 2/3 develops from 1st pharyngeal arch (lingual swellings and tuberculum impar) 

• posterior 1/3 develops from 3rd and 4th pharyngeal arches (copula and hyobranchial eminence)

• development of the tongue occurs around the 4th week 

• the tongue muscles are derived from occipital somites and are innervated by the hypoglossal nerve 

what nerve innervates tongue?

• hypoglossal nerve

what is tongue muscles derived from?

• occipital somites

when does development of tongue occur?

• around the 4th week 

what does posterior 1/3 of tongue develop from?

• from 3rd and 4th pharyngeal arches (copula and hyobranchial eminence)

what does the anterior 2/3 of the tongue develop from?

• 1st pharyngeal arch (lingual swellings and tuberculum impar) 

Lips

• upper lip - fusion of maxillary process and medial nasal prominence 

• Lower lip - fusion of mandibular prominences 

Palate 

• palate is developed by fusion of primary (intermaxillary segment) and secondary plate

• Primary palate - forms from medial nasal processes

• Secondary palate - form from palatal shelves of maxillary processes, which fuse by the 9th week

Jaws ratio

1. 2nd embryonic month - embryonic prognathism

2. 3rd embryonic month - embryonic progenia

3. Neonatal prognathism

4. 6 months after birth - orthognathism

Factors influencing the development of jaws, oral cavity floor and tongue

• irradiation

• chemical

• hromonal

• dietary

• stress

• genetic