Face Nose Embryology

1. Embryology of the
Face, Nose & PNS
Prepared by- Bisrat G. / ORL-HNS (R1)
Moderator- Dr Mesele /ORL-HNS
Surgeon/
Jan. 2018 GC

2. OUTLINE
 Development of the face
 Development of the Nasal cavities
 Formation of the nasal sac
 Formation of the nasal choanae
 Nasal septum development
 Palatal development
 Overview on some of the skull bones development
 Development of Paranasal sinuses
 List of anomalies

3. DEVELOPMENT OF THE FACE
 Facial development occurs mainly between the fourth and eighth
weeks.
 The facial primordia appear early in the 4th week around the large
primordial stomodeum
 The five facial primordia that appear as prominences around the
stomodeum are :
 The single frontonasal prominence
 The paired maxillary prominences
 The paired mandibular prominences

4. Cont…
 The frontal part of the FNP forms the forehead; the nasal part
of the FNP forms the rostral boundary of the stomodeum and
nose.
 The paired maxillary prominences form the lateral boundaries
of the stomodeum, and the paired mandibular prominences
constitute the caudal boundary of the stomodeum
 The five facial prominences are active centers of growth in
the underlying mesenchyme.

5. Cont...
 The lower jaw and lower lip are the first parts of the face to
form. They result from merging of the medial ends of the
mandibular prominences in the median plane.
 By the end of the fourth week, bilateral oval thickenings of the
surface ectoderm - nasal placodes - the primordia of the
nasal epithelium, have developed on the inferolateral parts of
the FNP.

6. Cont…
 This proliferation-driven expansion results in movement of the medial nasal
prominences toward the median plane and each other.
 Each lateral nasal prominence is separated from the maxillary prominence by a cleft
called the nasolacrimal groove.
 By the end of the sixth week, each maxillary prominence has begun to merge with
the lateral nasal prominence along the line of the nasolacrimal groove.
 Proliferation of mesenchyme in the maxillary prominences causes them to enlarge
and grow medially toward each other and the nasal prominences.

7. Cont…
 The nasolacrimal duct develops from a rod like thickening of ectoderm in the
floor of the nasolacrimal groove.

8. Cont…
 Merging of the medial nasal and maxillary prominences results in continuity of the
upper jaw and lip and separation of the nasal pits from the stomodeum.
 As the medial nasal prominences merge, they form an intermaxillary segment.
 The intermaxillary segment gives rise to:
 The middle part (philtrum) of the upper lip
 The premaxillary part of the maxilla and its associated gingiva (gum)
 The primary palate

9. Summary facial dev’t
 The frontal nasal prominence forms the forehead and dorsum and apex
of the nose.
 The lateral nasal prominences form the alae (sides) of the nose.
 The medial nasal prominences form the nasal septum, ethmoid, and
cribriform plate.
 The maxillary prominences form the upper cheek regions and the upper
lip.
 The mandibular prominences give rise to the chin, lower lip, and lower
cheek regions.

10. Cont…
 The lips and gingivae begin to develop when a linear thickening of the
ectoderm, the labiogingival lamina, grows into the underlying
mesenchyme.
 Gradually, most of the lamina degenerates, leaving a labiogingival
groove between the lips and the gingivae.
 A small area of the labiogingival lamina persists in the median plane to
form the frenulum of the upper lip, which attaches the lip to the gingiva.

11. Olfactory Placode
 Nasal cavity is the first seen as nasal placode in the 4th week of IU life.
 This is thickening of ectoderm above the stomodeum.
Olfactory pit
 Olfactory placode thicken and sinks into the mesenchymal tissue forming the
olfactory pit.
 This pit lies between the proliferating medial and lateral nasal folds of frontonasal
process.
 Olfactory pit deepens to form the nasal sac by the 5th week of gestation.

12. Some epithelial cells differentiate into
olfactory receptor cells (neurons).
The axons of these cells constitute the
olfactory nerves, which grow into the
olfactory bulbs of the brain

13. 12.5 mm embryo stage
 The maxillary process of 1st arch grows medially and anteriorly.
 Medially the maxillary process fuse with medial nasal folds and the frontonasal
process.
 The nasal pits becomes a closed off to form a widely separated primitive nasal
cavities.
 The primitive nasal cavity and mouth are separated by bucconasal membrane.

14. 15 mm stage
 The bucconasal membrane thins as the nasal sacs extend posteriorly & eventually
breaks down to form the choana.
 The primitive choana is placed more anteriorly than the definitive choana at this
stage.

15. Nasal cavity Development

16. Premaxilla
 Floor of the nasal cavity anterior to the primitive choana is
formed by mesenchymal extensions of medial nasal folds.
 These mesenchymal extensions give rise to premaxilla,
upper lip and
medial crus of lower
lateral cartilages.

17. Maxillary process
 It develops from the dorsal end of mandibular arch
 Joins the lateral nasal fold around the nasomaxillary groove.
 Ectoderm in the region of nasomaxillary groove canalizes to
form the nasolacrimal duct.
 The lateral nasal fold of FNP gives rise to nasal bones, upper
lateral cartilages & lateral crura of the lower lateral cartilages.

18. Nasal septum development
 Begins by 13.5 mm embryonic stage
 Begins the fusion of the maxillary and the frontonasal process
 Midline ridge develops from the posterior edge of FNP in the roof
of the oral cavity
 This ridge extends posteriorly up to the rathke’s(adenohypophysial)
pouch.
 This ridge gives rise to the nasal septum

19. Primitive nasal septum
 The primitive nasal septum is entirely made of
cartilage
 The superior portion of this nasal septum ossifies to
form the perpendicular plate of ethmoid.
 Posterior lower portion of this cartilage ossifies to
form the vomer
 The anterior inferior portion persists as the
quadrangular cartilage
 Two ossification centers appear in the region of
vomer which ossify to form a groove on which the
septal cartilage sits

20. VNO /Vomeronasal Organ/
 On either side of the anterior septum close to the paraseptal
cartilage invagination of ectoderm occurs.
 This invagination gives rise to the Vomeronasal organ
 This disappears in humans leaving behind a blind tubular pouch 2-
6 mm long
 They involute during later life leaving behind a small cartilaginous
bulge

21. Development of Palate
 Palate is derived from lateral maxillary processes
 These processes grow medially towards each other and the
nasal septum
 Initially the palatal processes lie lateral to the tongue
 Palatal processes swing medially and the fusion starts
horizontally
 Fusion begins along the posterior margin of the primitive
palate

22. Cont…
 The palate develops in two stages:
 The development of a primary palate
 The development of a secondary palate
 Palatogenesis begins in the 6th week; however, development of the
palate is not completed until the 12th week.
 The critical period of palate development is from the end of the 6th
week until the beginning of the 9th week.

23. Primary Palate
 Early in the sixth week, the primary palate- median
palatal process (intermaxillary segment)- begins
to develop.
 The primary palate forms the anterior/midline
aspect of the maxilla, the premaxillary part of the
maxilla.

24. Secondary Palate
 is the primordium of the hard and soft parts of the palate
 early in the 6th week from two mesenchymal projections that extend from the
internal aspects of the maxillary prominences.
 The lateral palatal processes (shelves)-project inferomedially on each side of the
tongue
 Concurrently, bone extends from the maxillae and palatine bones into palatal
processes to form the hard palate
 The median palatine raphe indicates the line of fusion of the palatal processes.

27. Development of PNS
 25weeks – 3 medial projections from lateral wall of nose
 Diverticula occurs between these projections towards the choana (forms
the meati of nose)
 They form from outgrowths or diverticula of the walls of the nasal cavities
and become pneumatic (air-filled) extensions of the nasal cavities in the
adjacent bones,
 such as the maxillary sinuses in the maxillae and the frontal sinuses in the frontal
bones.

28. Development of PNS (cont..)
 The anterior most projection –agger nasi
 Inferior maxilla turbinate projection – inferior turbinate and
maxillary sinus
 Superior projection ethmoidal turbinate - superior turbinate,
middle turbinate, ethmoidal air cells &their drainage system
 Middle meatus develops between inferior & middle
turbinates.

29. Development of Maxilla
 Maxilla develops during 6-7 weeks from 5 ossification centers
 These ossification centers gives rise to alveolar ,palatine, zygomatic
and frontal processes of maxilla and the floor of orbit
 Ossification center in the medial floor of pyriform aperture forms
the premaxilla
 Premaxilla gives rise to upper incisors and anterior nasal spine

30. Development of Ethmoid
 Ethmoid ossifies in the cartilaginous nasal capsule - 3centers
 One center for each labyrinth and one for the perpendicular plates
 These centers appear during 4-5th month of intrauterine life
 Perpendicular plate and crista galli develop from the same center
during the 1st year of life, fuses with the labyrinth during 2nd year

31. Development of frontal
 Develops from 2 centers – 8th week
 Centers are present in supra ciliary ridge
 At birth frontal bone – 2 halves separated by frontal (metopic
suture)
 Development completes by 8th year

32. Development of sphenoid
 Develops from pre sphenoidal & post sphenoidal portions
 These portions fuse during the 8th intrauterine month
 At birth sphenoid consists of three portions; central portion – body
and lesser wings and Lateral portion – greater wing & pterygoid
process.
 These portions fuse during the first year of life.

33. Pre sphenoidal portion
 Lies anterior to tuberculum sella.
 Continous with lesser wings of sphenoid
 Made of 6 ossification centers

34. Post sphenoidal portion
 Composed of sella turcica and dorsum sellae
 Gives rise to greater wings of sphenoid and pterygoid process
 This portion has 8 ossification centers

35. Development of maxillary sinus
 First sinus to appear – 7- 10 wks
 Shallow groove expanding from primitive
infundibulum to the maxilla
 Enlarges by absorption & expansion
 Grows till 17 yrs of life

36. Development of ethimoid sinus
 Develops during 9-10 wks of gestation
 Has Anterior and posterior groups
 Small before the age of 2 years
 3-4 air cells present at birth
 begin to grow rapidly at 6 to 8 years of age.

37. Sphenoid sinus – Development
 Develops as evagination of sphenoethimoidal recess – 3rd IU month
 Presents as a small cavity at birth
 Reaches full size at the age of 7
 Pneumatization progresses at a rate of 0.25mm / per year from the
age of 4
 In extreme cases of pneumatization the optic nerve and the internal
carotid artery may lie naked within the sinus cavity

38. Frontal sinus – development
 Most variable
 Embryologically anterior ethimoidal air cell
 Direct continuaton of infundibulum and frontal recess
 Upward migration of anterior ethimoidal air cells
 Remains as cul – de- sac within the frontal bone at 2
years of age

39. Anomalies
 Failure of this fusion – bifid uvula to clefts of varying degrees
 Failure of fusion between maxillary process and premaxilla causes cleft lip
 Failure of fusion between maxillary process and lateral processes – nasolacrimal furrow
 Non fusion of palatine processes and septum – cleft palate
 Failure of rupture of oronasal membrane – choanal atresia
 Failure of olfactory placode development – complete / partial absence of nose

40. Cont….
 Unilateral maldevelopment of olfactory placode – Proboscis lateralis
 Premature fusion of pre & Post sphenoid segments – depression of nasal
bridge(achondroplasia), hypertelorism
 Epithelial entrapment along fusion lines causes cysts

41. Dermoid
 Commonest inclusion cyst
 It is a median lesion
 May be superficial or may communicate intracranially via cribriform plate (45%)
 Cranial theory – as dura mater recedes it pulls the nasal ectoderm forming a sinus
which later gets pinched off to form the cyst
 Entrapment theory – ectoderm may get entrapped between the two median nasal
folds

42. Cont…
Encephaloceles –
 Usually present at birth as a midline nasal mass, nasal obstruction, or CSF leak.
 Encephaloceles are compressible, trasilluminate and enlarge with crying.
Gliomas –
 Usually present at birth.
 Gliomas are non-compressible and do not trasilluminate.

43. Anomalies
 Mandibulofacial Dysostosis (Treacher Collins syndrome)
 Congenital microstomia (small mouth) results from excessive merging of the
mesenchymal masses in the maxillary and mandibular prominences of the first
pharyngeal arch.
 Sometimes may be associated with underdevelopment (hypoplasia) of the
mandible.
 Facial Clefts
 Oblique facial clefts (orbitofacial fissures) are often bilateral and extend from the
upper lip to the medial margin of the orbit. When this occurs, the nasolacrimal
ducts are open grooves (persistent nasolacrimal grooves).

44. Bibliography
Medscape
Online Sources

45. THANK
YOU