THE DEVELOPMENT OF

THE FACE
LEC.3
BY
DR. SUHAIR MAJEED
2020-2021
 DEVELOPMENT OF THE FACE
*During early development (4 weeks in utero), the stomodeum is bounded by five
facial swellings, produced by of mesenchyme below the ectoderm, these are:
--The frontonasal process lies above, the two mandibular processes lie below,
and the two maxillary processes are located at the sides.
* At this early stage, a membrane ( oropharyngeal membrane) separates the
primitive oral cavity from the developing pharynx.
*The oropharyngeal membrane is composed of an outer ectodermal layer and
an inner endodermal layer.
*This membrane soon breaks down to establish continuity between the
ectodermally lined oral cavity and the endodermally lined pharynx.
EARLY DEVELOPMENT OF THE FACE
CONT.

*In 5th week , localized thickenings of ectoderm give rise to Nasal and lens
placodes.
*These placodes will form olfactory epithelium and lenses of the eyes .
*The nasal placodes sink into the underlying mesenchyme, forming two blind-ended
Nasal pits (the primitive nasal cavities).
*Proliferation of mesenchyme from the frontonasal process around the openings of
the nasal pits produces the Medial and lateral Nasal processes.
*The nasal pits continue to deepen until they approach the roof of the primitive oral
cavity, being separated from it by Oronasal membranes.
* By the end of the fifth week, these membranes rupture to produce
communications between the developing nasal and oral cavities.
NASAL &LENS PLACODES / MEDIAL &LATERAL NASAL PROCESSES
CONT.

*In the 6-week-old embryo, the two mandibular processes fuse in the midline to
form the tissues of the lower jaw.
*The mandibular processes and maxillary processes meet at the angle of the
mouth, thus defining its outline.
* maxillary processes continue growing and merge laterally with mandibular
processes to form the cheeks.
* Their growth compresses two medial nasal processes and causes them to fuse .
*Then the bridge of the nose ,and intermaxillary segment is established.
*This segment yields the portion of upper lip containing the philtrum , upper jaw
with 4 incisors ,and primary palate.
*Medial nasal process fuses with maxillary process, giving rise to a smooth
upper lip.
DEVELOPMENT OF THE FACE
CONT.

* Between the merging maxillary and the lateral nasal processes lie the
nasolacrimal furrows.
*From each furrow a solid ectodermal rod of cells sinks below the surface and
canalizes to form the nasolacrimal duct.
*lateral nasal process giving rise to the alae of the nose .
*The lower jaw appears early in facial development and is formed by fusion
of the paired mandibular processes.
* Rapid growth of mesenchyme within each mandibular process causes their
movement toward the midline where they merge, and formed the lower lip, chin,
and mandible .
 DEVELOPMENT OF THE FACE

Frontonasal process Frontonasal process

Lateral
nasal
Lateral nasal process
process
eye Medial
nasal Nasal
Nasolacrimal pit
process Medial nasal
groove
process

Mandibular Nasolacrimal furrow

process
Maxillary process

mouth
 DEVELOPMENT OF SECONDARY PALATE
*Initially there is a common oronasal cavity bounded anteriorly by the primary
palate & occupied mainly by the developing tongue.
*Formation of secondary palate starts around 7th to 8th week of embryo, and
completed around 3rd month of gestation.
*In the oral cavity these outgrowth appeared:
- Two palatine shelves or lateral maxillary process
-Nasal septum
*From the frontonasal process, nasal septum grows downward along the midline.
*Growth of the palatal shelves continues towards the midline.
*During the 7th week of development, the oral part of the oronasal cavity becomes
completely filled by the developing tongue.
*The two shelves first directed downward on each side of the developing tongue.
 DEVELOPMENT OF PALATE
Medial
nasal Lateral nasal Medial nasal processes
processes process
Maxillary
Maxillary process process

Lateral palatal fold

(maxillary process)

Forming nasal septum(frontonasal

process)
CONT.

*After 7th week of development, the tongue withdrawn from between the shelves
, which now elevate & fuse with each other (above the tongue) &with primary palate.
*Two palatal shelves fuse along the midline, and separating the primitive cavity
into oral and nasal cavities.
*Between 7-8th weeks , the tongue and mandible are small, and positioned
behind the lower lip.
* As Two palatine shelves meet, adhesion of the epithelium occurs, and become
indistinguishable from one another .
*to achieve this fusion, DNA synthesis ceases (stopped)within the epithelium
some 24-36 hours before epithelial contact.
*these cells have a carbohydrate – rich surface coat, that permits adhesion and
the formation of junction to achieve fusion of the processes.
DEVELOPMENT OF THE FACE & PALATE
CONT.

* Fusion of the palatal processes is completed by the 12th week of development.

*Behind the secondary nasal septum, the palatal shelves fuse to form the soft
palate and uvula.
*Once fusion is complete, the hard palate ossifies intramembranously from four
centers of ossification, one in each developing maxilla and one in each developing
palatine bones.
 Median upper lip
Wing of nose
External nares External
nares

Primary palate

Incisive
foremen
Primary
palate
Secondary
palate

Secondary
palate Soft palate
and uvula

Forming nasal septum

 THE DEVELOPMENT OF MAXILLA

* The maxilla develops from a center of ossification in the mesenchyme of

the maxillary process of the first pharyngeal arch.
* The center of ossification is associated closely with the cartilage of the
nasal capsule.
* From this center, bone formation spreads posteriorly below the orbit
toward the developing zygoma and anteriorly toward the future incisor region .
* Ossification also spreads superiorly to form the frontal process.
*As a result of this bone deposition, a bony trough forms, for the
infraorbital nerve.
* From this trough ,a downward extension of bone forms the lateral
alveolar plate for the maxillary tooth germs.
DEVELOPMENT OF MAXILLA
CONT.

* The medial alveolar plate develops from the junction of the palatal process
and the main body of the forming maxilla.
*A secondary cartilage also contributes to the development of the maxilla.
A zygomatic cartilage appears in the developing zygomatic process and for a short
time adds to the development of the maxilla.
*The body of the maxilla is small because the maxillary sinus has not
developed, the sinus is formed during 16th week of development.
THE MAXILLA
 CRANIOFACIAL SKELETON DEVELOPMENT

* The skull consists of Cranial vault, Cranial base ,and Face.

* The skull divided into :
- Neurocranium, is the upper &back part of the skull, which forms a
protective case around the brain.
- Viscerocranium, the skeleton of the face and jaw.
*Neurocranium can be subdivided into :
- Membranous part ,which forms the cranial vault( mainly flat bones)
surround the brain .
- Cartilaginous part which forms bones of the base of skull (cranial base ).
- Cranial vault consists of (paired frontal and parietal bones,squamous parts of
temporal bone, and interparietal part of Occipital bone.
THE SKULL (NEUROCRANIUM &VISCEROCRANIUM)
CONT.

-All cranial vault bones are formed by intramembranous ossification ,in which
direct laying down of bone into the mesenchyme .
* Cranial base includes these bones : ethmoid , sphenoid ,occipital, paired
frontal ,and paired temporal bones.
*All cranial base bones, are formed by endochondral ossification(which
involves cartilage as a precursor).
*The Viscerocranium or facial skeleton , includes these bones :
- vomer , inferior nasal conchae, nasal bones, maxilla, mandible, palatine,
zygomatics, and lacrimals.
*Bones of the face also formed by intramembranous ossification.
THANK YOU