The document details the embryological development of the human face, starting from the 4th week of intrauterine life, including the formation of key structures like the maxilla, nasal processes, and anatomy of the lips. It also discusses mechanisms for postnatal growth of the maxilla and outlines several clinical considerations related to facial development anomalies such as hare lip and macrostomia. The growth processes involved include displacement, growth at sutures, and surface remodeling, highlighting how these factors contribute to the formation and size change of facial structures.

1. DEVELOPMENT
OF THE
FACE
D R A M I T H A G , B D S , M D S
O R A L A N D M A X I L L O F A C I A L P A T H O L O G Y

2. Face develops in humans between 4th – 10th
week of intrauterine life.

3. PRENATAL GROWTH OF THE MAXILLA
4th week of intrauterine life
- Formation of the head fold
- Following which the developing brain and the pericardium form 2 prominent bulges on
the ventral aspect of the embryo.
- The 2 bulges are separated from each other by  a shallow depression called
stomatoedum (corresponding to the primitive mouth).
- Floor of the stomatodeum is formed by the Buccopharyngeal membrane, which
separates the stomatodeum from the foregut.

4. - Soon, mesoderm covering the developing
forebrain proliferates, and forms a
downward projection that overlaps the
upper part of the stomatodeum – this
downward projection is called frontonasal
process.

5. - During the same time (4th week of intrauterine life) five
branchial arches form in the region of the future head and
neck region
- The first branchial arch is called – mandibular arch and play
an important role in the development of the nasomaxillary
region.
- The mandibular arch forms the lateral wall of the
stomatodeum.
- This arch gives off a bud from its dorsal end – this is called
maxillary process (4th week).
- It grows ventromedially cranial to the main part of the arch
- Main part of the arch is now called mandibular process.

6. - Therefore the face is derived from
- Frontonasal structures
- First pharyngeal (mandibular) arch of each side

7. 5th week of intrauterine life
- The ectoderm overlying the frontonasal process soon shows bilateral
localized thickenings that are situated a little above (caudal or
raustral to) the stomatodeum. These are the nasal placodes or
olfactory placodes.
- The formation of these placodes is induced by the underlying
forebrain.
- The placodes soon sink below the surface to form the nasal pits.
- The nasal pits are continuous with the stomatodeum below.
- The edges of each pit are raised above the surface
- Medial raised edge is called – medial nasal process.
- Lateral raised edge – called lateral nasal process

8. - Now, all the primordial for the formation of lip and primary
palate are present
- Medial nasal process
- Lateral nasal formed
- Maxillary process

9. DEVELOPMENT OF UPPER LIP
- Maxillary process enlarges
- Maxillary process now grows medially and approaches the
lateral and medial nasal processes but remains separated
from them by distinct grooves (naso-optic groove and
bucco nasal groove)
- From each furrow or groove  a solid ectodermal rod of
cells sink below the surface and canalizes to form
nasolacrimal duct.

10. - Medial growth of the maxillary process further fuses
first with the lateral nasal process and then medial
nasal process.
- The medial and lateral nasal processes also fuse with
each other.
- This way the nasal pits  now called external nares
are cut off from the stomatodeum

11. - The maxillary process undergoes considerable growth
 therefore, pushes the medial nasal process towards
the midline, where it merges with its anatomic
counterpart from the opposite side.
- At the same time the frontonasal process becomes
much narrower from side to side, with the result that
the 2 external nares come close to each other.

12. 6th week of intrauterine life
- 2 theories have been proposed for the continued development of the upper lip beyond the
6th week.
1st theory
- Mesenchyme of the maxillary process entirely overgrows the mesenchyme of the medial
nasal process to meet in the midline and thus contribute all the tissue for the upper lip.
- This is based on the fact
 Maxillary process  supplied by maxillary nerve
 Fronto nasal process  by opthalmic nerve
 Fully formed upper lip  supplied by infraorbital branch of the maxillary nerve)

13. 2nd theory
- Maxillary process merely meets the medial nasal process without any overgrowth or
mesenchymal invasion.
- Therefore the middle third of the upper lip is derived from the merged medial nasal process
of frontonasal process.
- Histological evidence favours this

14. Mouth
- Stomatodeum is now bounded above by the Upper lip which is derived as follows
o Mesoderm of the lateral part of the lip is formed from the maxillary process.
o The overlying skin is derived from ectoderm covering this process
o Mesoderm of the median part of the lips (philtrum) is formed from the frontonasal
process.
o Ectoderm of the maxillary process overgrows this mesoderm to meet that of the opposite
maxillary process in the midline
o As a result skin of the entire upper lip is innervated by the maxillary nerves.
o Muscles of the face (including the lips)  are derived from the mesoderm of the second
branchial arch and are therefore supplied by facial nerve.

16. Development of lower lip
- At 6th week of embryo
- The mandibular process of the 2 sides grow towards each
other and fuse in the midline
- They form the lower margin of the stomatodeum.
- The fused mandibular process gives rise to lower lip and
the lower jaw

17. Development of nose
- Nose receives contributions from
 Frontonasal process
 Medial nasal process
 Lateral nasal process
- External nares are formed when the nasal pits are cut off from the stomatodeum by the fusion
of the maxillary process with medial nasal process.
- The external nares gradually approach each other as the maxillary process grows  pushing
the frontonasal process towards each other.

18. - Deeper part of the frontonasal process  forms nasal septum
- Mesoderm becomes heaped up in the median plane to form the prominence of the nose.
- Simultaneously a groove appear between the region of the nose and the bulging forebrain
(now called forehead)
- As the nose becomes prominent  the external nares comers to open downeards instead
of forwards.
- The external form of the nose is thus formed.

19. DEVELOPMENT OF CHEEKS
- After formation of the upper and lower lips, the stomatodeum (now called mouth) is very
broad.
- In its lateral part it is bounded
 Above by the maxillary process
 Below by the mandibular process
- These process undergo progressive fusion with each other to form cheeks
- The maxillary process fuses with the lateral nasal process  in the region of the lip + extends
from the stomatodeum to medial amgle of the developing eye this line of fusion is marked
by a groove called the naso optic furrow or nasolacrimal sulcus
- A strip of ectoderm becomes buried along this furrow and gives rise to the nasolacrimal duct.

20. POST NATAL GROWTH OF THE MAXILLA
- Growth of the nasomaxillary complex is produced by the following mechanisms
o Displacement
o Growth of the sutures
o Surface modeling
Displacement
- 2 types of displacement
 Primary displacement (bone is displaced by its own enlargement)
 Primary displacement of the maxilla  in a forwards direction
 This occurs by growth of the maxillary tuberosity in a posterior direction
 This results in the whole maxilla being carried anteriorly
 The amount of forwards displacement = amount of posterior lengthening

21.  Secondary or passive displacement (bone is not displaced by its own enlargement, rather a
passive displacement by the growth of the cranial base)
 Maxilla is attached to the cranial base by means of a number of sutures
 Therefore when the cranial base grows  produces a direct effect on the nasomaxillary
complex
 Cranial base grows  Middle cranial fossa grows anteriorly  therefore the passive
pressure produced by the cranial base  pushes the nasomaxillary complex  downwards
and forwards.

22. Growth at the sutures
- Maxilla is connected to the cranium and cranial base by a number of sutures
 Fronto nasal suture
 Fronto maxillary suture
 Zygomaticotemporal suture
 Zygomatico maxillary suture
 Pterygo palatine suture

23. - These sutures are oblique and almost parallel to each other
- This allows the downward and forward repositioning of the maxilla as growth occurs at
these sutures.
- Tension related bone formation occurs at sutures.
- Growth of the surrounding soft tissues  carries the maxilla downeards and forward 
leading to opening up of space at the sutural attachements  new bone is now formed on
either side of the suture  increasing the overall size of the bones on either side.

24. Surface remodeling
- Remodeling of bone by bone deposition and resorption occurs to bring about
 Increase in size
 Change in shape of the bone
 Change in functional relationship.
- Bone remodeling changes taking place in nasomaxillary complex are
 At the orbital rim
 Lateral surface  resorption
To compensate
 Medial surface of the rim  deposition
 External surface of the lateral rim  deposition

25.  At the Orbital floor
 Orbital floor faces superiorly, laterally and anteriorly
 Surface deposition occurs here and results in  growth in a superior, lateral and anterior direction
 At the maxillary tuberosity
 Bone deposition occurs along the posterior margin  causing the lengthening of the dental arch  and
enlargement of the antero posterior dimension of the entire maxillary body  helps accommodating the
erupting molars.
 At the nose
 Laterall wall of nose  resorption  leading to increase in size of the nasal cavity
 Floor of the nasal cavity
 Floor of the nasal cavity  resorption
To compensate
 Palatal aspect  deposition  therefore net downward shift occurs  leading to increase in maxillary height

26.  At the zygomatic bone
 Anterior surface  resorption
 Posterior surface  deposition
 The zygomatic bone  moves in a posterior direction.
 At zygomatic arch
 Lateral surface  deposition
 Medial surface  resorption
 Anterior nasal spine  bone deposition  becomes prominent
 Alveolar margins  As teeth erupts  deposition  increasing the maxillary height and
depth of the palate.
 Maxillary sinus  entire wall of the sinus except the mesial wall  undergoes resorption 
results in increase in size of maxillary antrum.

27. CLINICAL CONSIDERATIONS
- Since the formation of various parts of the face involves fusion of diverse components.
- Occasionally this fusion can be incomplete  give rise to various anomalies

28. HARE LIP
- Upper lip of the hare normally has a cleft
- Hence the term hare lip is used for defects of the lips.
- When 1 or both maxillary processes do not fuse with the
medial nasal process  this gives rise to defects in upper lip.
- This may vary in degree
- Unilateral or bilateral

29. b) Defective development of lowermost part of the
frontonasal process  give rise to a midline defect of ht
upper lip
c) When 2 mandibular process  do not fuse  with each
other  lower lip shows a defect in midline  the defect
usually extends to the jaw.

30. OBLIQUE FACIAL CLEFT
- Non fusion of the maxillary an dlateral nasal processes gives rise to a cleft running from the
medial angle of the eye to mouth.
- Nasolacrimal duct is also not formed.

31. MACROSTOMIA
- Inadequate fusion of mandibular and maxillary processes with each other  leads to
abnormally wide mouth  macrostomia
LATERAL FACIAL CLEFT
- Unilateral lack of fusion of mandibular and maxillary process  forms LATERAL FACIAL
CLEFT.
MICROSTOMIA
- Too much fusion of mandibular andmaxillary processes  may result  in small mouth

32. MANDIBULOFACIAL DYSOSTOSIS OR FIRST ARCH SYNDROME
- Entire first arch may remain underdeveloped on one or both sides, affecting
 Lower eyelid
 Maxilla
 Mandible
 External ear.
- Prominence of the cheek is absent
- Ear is displaced ventrally and caudally

33. HEMIFACIAL HYPERTROPHY
- One half of the face is overdeveloped
HEMIFACIAL ATROPHY
- One half of the face is under developed
RETROGNATHIA
- Mandible may be small compared to the rest of the face resulting in a receding chin.
HYPERTELORISM
- Eyes may be widely separated
PARAMEDIAN OR COMMISURAL PITS
- Lips showing congenital pits or fistula
DOUBLE LIP
- Lips are double

34. CONGENITAL TUMORS
- May be present in relation to the face.
ANOMALIES OF NOSE
Nose may be bifid
One half of nose is absent
Proboscis – nose forms a cylindrical projection jutting out from just below the forehead.
This anomaly may sometimes affect only one half of the nose and usually associated with
fusion of the eyes  Cyclops

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