Maxillofacial Embryology - Basic Science Core

Embryology Exam 1

Human Face Prominences

The human face develops from 5 elevated “prominences”, note that different references may use “swelling” or “process” they’re referring to the same thing

Facial prominences consist predominantly of:

• neural crest derived mesenchyme from first pharyngeal arches

At week 4, the 5 prominences surround the stomodeum:

• Prominences 1&2:

 Maxillary prominences

 LATERAL to the stomodeum

• Prominences 3&4:

 Mandibular prominences

 CAUDAL to the stomodeum

• Prominence 5

 Frontonasal prominence

Bucco-pharyngeal membrane

Bucco-pharyngeal membrane will rupture to allow

continuity between oral and pharyngeal cavity

During week 5 …

Nasal placodes invaginate form

nasal pits

• Nasal prominences

• A new ridge of tissue forms on each side of the pits

• This forms the:

1) Medial Nasal Prominence

2) Lateral nasal prominence

Nasal prominences formed in week 5 (2)

• Nasal prominences

• A new ridge of tissue forms on each side of the pits

• This forms the:

1) Medial Nasal Prominence

2) Lateral nasal prominence

In Weeks 6 to 10:

Let’s start with the lips

 Maxillary prominences increase in size and grow

medially compressing the medial nasal prominences

toward the midline

 The CLEFT between the medial nasal prominence and

the maxillary prominence is LOST (or should be) and the

two structures fuse

 The UPPER LIP is formed by

WO MEDIAL NASAL PROMINENCES and the TWO

MAXILLARY PROMINENCES

 The LOWER LIP & MANDIBLE are formed by

 MANDIBULAR prominences that merge across the

midline

The UPPER LIP is formed by

TWO MEDIAL NASAL PROMINENCES and the TWO

MAXILLARY PROMINENCES

The LOWER LIP & MANDIBLE are formed by

• MANDIBULAR prominences that merge across the midline

Nasolacrimal groove

• deep furrow separating maxillary and lateral nasal prominences

• Weeks 6-10

nasolacrimal duct

• Ectoderm forms a canal at the base of the groove

Nasolacrimal sac

Upper end of the duct forms the nasolacrimal sac

Once the nasolacrimal duct is formed

the maxillary and lateral nasal prominences merge (or they’re

supposed to…)

The nose development

The NOSE is formed from 5 facial

prominences

 Frontonasal prominence forms the

bridge

 Merged medial prominences form

the crest and tip

 Lateral nasal prominences form

the alae

INTERMAXILLARY SEGMENT (I.S)

By week 7, merging of the maxillary prominences and the

medial nasal prominences creates the INTERMAXILLARY

SEGMENT(I.S.)

• The I.S. is continuous with the rostral portion of the nasal

septum which is formed by the frontal prominence

INTERMAXILLARY SEGMENT(I.S.) Three Components

• Labial component = philtrum of the upper lip

• Upper jaw component = four incisor teeth

• Palatal component = triangular primary palate

Also around weeks 6-7 the Secondary Palate begins to fuse

The primary palate is relatively small compared to

the secondary, but the secondary becomes the

main part of the definitive palate

○ Formed by two shelf-like outgrowths from the

maxillary prominences called the palatine shelves

○ Fusion of the palatal shelves begins in the

anterior palate and progresses posteriorly

○ The shelves also ascend to horizontally position

above the tongue and fuse

○ The nasal septum grows down and joins the newly

formed palate

Incisive Foramen

Anteriorly, the palatal shelves fuse with the triangular

primary palate and the incisive foramen is the midline

landmark between the primary and secondary plates

Nasal Cavity, weeks 6 through 9 (Nasal pits deepen)

• Growth of surrounding tissue

• Penetration into the underlying mesenchyme

Oronasal membrane

• Separates the pits from the primitive oral cavity via the foramina named primitive choanae

• Choana (“ko-eh-na”) = funnel in Greek

• Choanae lie on each side of the midline immediately behind the primary palate

Definitive choanae once the palate forms and the nasal chambers develop

- they lie at the junction of the nasal cavity

and pharynx

Paranasal air sinuses develop as

diverticula of the lateral nasal wall and extend into the maxilla, ethmoid, frontal, and sphenoid bones, reaching definitive size at puberty