Lectures of Human Embryology By Dr. Noura El Tahawy Faculty of Medicine; El Minia University; Egypt

1. Development of the face
By
Dr. Noura El Tahawy
Special Embryology

2. INTRODUCTION
Anatomical structures are more diverse in the mouth than in any other region.
The human face begins to form during the 4th week of embryonic development.
By the 6th week the external face is completed.
 Between the 6th and 8th weeks the development of the palate subdivides nasal and oral cavities.
 This development continues into the 12th week with completion of the soft palate.

3. DEVELOPMENT OF FACE
• Face develops from 3 prominences that surround the stomatodeum
1. One frontonasal process
2. Right and Left maxillary processes (from first pharyngeal arch)
• 3- Right& left Mandibular processes (from the first pharyngeal arch).
•N. B. Stomodeum is a depression bounded cranially by a bulging produced by the brain and caudally by a bulging produced by the pericardial cavity.
* From each side of lower part of frontonasal process two mesodermal processes appear called medial& lateral nasal processes (they will give the nasal cavities in the future.

4. Maxillary process
DEVELOPMENT OF FACE
Mandibular process
Mandibular process
Maxillary process
Fronto-Nasal process

7. DEVELOPMENT OF FACE

8. 8
•Lateral view of an embryo at the end of the fourth week, showing position of the pharyngeal arches .B .Frontal view of a 4.5-week embryo showing the mandibular and maxillary prominences. The nasal placodes are visible on either side of the frontonasal prominence .C .
Scanning electron micrograph of a human embryo at a stage similar to that of B .

9. Frontal aspect of the face .A. 5-week embryo .B . 6--week embryo. The nasal prominences are gradually separated from the maxillary prominence by deep furrows .
Development of face

10. DEVELOPMENT OF FACE
A, Frontal aspect of the face .A . 7-week embryo. Maxillary prominences have fused with the medial nasal prominences .
B . 10- week embryo

11. DEVELOPMENT OF UPPER LIP
Each maxillary process grows medially and fuses first with the lateral nasal process and then with medial nasal process.
The medial and lateral nasal processes fuse with each other in the nasal pits (ext. nares) are cut off from stomatodaeum.
The mesodermal basis of the lateral part of the lip is formed from the maxillary process and the overlying skin is derived from the ectoderm covering this process.
The mesodermal basis of the median part of lip (philtrum) is formed from frontonasal process.
The skin of the entire upper lip is innervated by maxillary nerves.
The muscles of the face along with the lips are derived from mesoderm of second bronchial arch, are supplied by the facial nerve.

13. DEVELOPMENT OF LOWER LIP
The mandibular process of two sides grow towards each other and fuse in the midline. The fused mandibular processes give rise to lower lip& to lower jaw.

14. DEVELOPMENT OF CHEEK
• After the formation of the upper lip and lower lips the stomatodaeum becomes broader.
• In its lateral part it is bounded by the maxillary process from above and mandibular process from below.
• Progressive fusion of both the processes form the cheek.

15. FACIAL MUSCLES
Muscles of face develop from 2nd branchial arch and are supplied by facial nerve

16. DEVELOPMENT OF FACE
• The cheek is formed by the fusion of posterior part of maxillary and mandibular process.
• The nose is derived from the frontonasal process.
• The nasal cavity is formed by enlargement of the nasal pits.
• Paranasal sinuses appear as outgrowths from the nasal cavity.
• The palate is formed by fusion of 3 components i.e right and left palatal processes and the primitive palate.
• The oral cavity is derived party from the stomatodaeum (ectoderm) and partly from the foregut(endoderm).

17. DEVELOPMENT OF FACE
• The pharynx is derived from the foregut.
• Muscles of face develop from 2nd branchial arch and are supplied by facial nerve
.
• Eyes develop from three sources:
- Neuroectoderm of the forebrain - retina, optic n.
-Surface ectoderm of the head - lens
-Mesoderm between these layers – eye muscle and vascular tissues.
• External ear develops from Ext. Acoustic meatus, middle ear develops from tubotympanic recess that is derived from 1st pouch and internal ear is derived from otic placode which is a thickening of surface ectoderm.

19. DEVELOPMENT OF NOSE

23. DEVELOPMENT OF THE NOSE
• The nasal cavities are separated from the mouth by the development of palate. The narrowing of the fronto-nasal process and the enlargement of nasal cavities brings them closer together.
• The intervening tissues becomes much thinned to form the nasal septum.
• The nasal pits now deepen to form the nasal sacs which expand both dorsally and caudally. The nasal sac has a ventral orifice that opens on the face is called the Anterior nares.

24. Structures Formed
Prominence
- One in number
- Forms: Forehead, bridge of nose, and medial and lateral nasal prominences
Frontonasal
- One on each side. Merge with the lateral nasal process then with the medial nasal process to form:
-Part of Cheeks, Upper lip except the median part (Philtrum); Upper Jaw except median part; Definitive palate
Maxillary (Two)
-- Two arise from lower border of frontonasal process; one on each side medially. - Merge with each other in the middle line to form intermaxillary segment which will give:
- Philtrum of upper lip; Median part of upper jaw (carrying 4 incisors); Primitive palate; Primitive nasal septum; crest& tip of the nose
Two Medial nasal (from frontonasal Process)
-Two arise from lower border of frontonasal process; one on each side laterally. Separated from the maxillary process by cleft where the nasolacrimal duct lies - Give: Alae of nose
Two Lateral nasal (from frontonasal process)
- One on each side below the maxillary processes. Merge with its fellow of other side to form: - Whole Lower lip; Whole lower jaw; Most of cheek
Mandibular (two)
Summary: Structures Contributing to Formation of the Face

25. CORRELATION BETWEEN SENSORY& MOTOR NERVE SUPPLY OF THE FACE AND ITS DEVELOPMENT
The process and its derivatives
Nerve supply
Frontonasal process
Ophthalmic nerve from trigeminal (First arch nerve)
Maxillary processes
Maxillary nerve from trigeminal (First arch nerve)
Mandibular processes
Mandibular nerve from trigeminal
(First arch nerve)
The muscles of the face (Facial expression muscles) along with the lips are derived from mesenchyme of second bronchial arch, Thus they are supplied by the facial nerve.

26. SUMMARY: DEVELOPMENT OF THE NOSE
Formed of proliferation of mesoderm ventral to forebrain
1- Frontonasal process formation
-2 oval ectodermal thickenings on the surface of lateral parts of frontonasal process
2 . Nasal placodes
-Mesoderm proliferation occurs around the nasal placodes
- Horse shoe- shaped
- On the sides of nasal placodes, the proliferation forms the medial & lateral nasal prominences
- Nasal pits: occur in the center of each of them
3. Lateral& Medial nasal prominences
-Results from fusion of medial nasal prominences
-It will give rise: philtrum of upper lip, primitive nasal septum, & median part of the upper jaw (carrying 4 incisors) & the primitive palate
3. Premaxilla
- Extension of the maxillary process below the nasal pit converts the pits into primitive cavity
4. Nasal cavity
-Primitive septum: formed by intermaxillary segment of frontonasal process
-Definitive septum: formed by proliferation of mesoderm of the roof of stomodeum
-grows & divides nasal cavity into Rt & Lt halves
5. Nasal septum
-Nasolacrimal groove is formed between maxillary process & latera. nassal fold. By 5 th week fusion of the two processes occurs
-Beneath the line of fusion solid cord of cells appear, then canalized & its cranial end expanded to from the lacrimal sac.
6. Nasolacrimal duct

27. 27
Intermaxillary segment and maxillary processes .B .The intermaxillary segment giving rise to the philtrum of the upper lip, the median part of the maxillary bone with its four incisor teeth, and the triangular primary palate .
DEVELOPMENT OF THE PALATE

28. SUMMARY OF DEVELOPMENT OF THE PALATE
I. Stage of formation of processes:
1- Formation of Primitive or Primary Palate
• By 5 th week: Intermaxillary process of frontonasal process 1ry palate later becomes the premaxilla of hard palateIncisive fossa. (the anterior triangular area bounded by the 4 incisor teeth).
2. Formation of Definitive (secondary) palate
• Maxillary processes  palatine processes 2ry palate  meeting& fusion with 1ry palate.
II. Stage of meeting& fusion of the processes:
• Palatine processes grow medially& fuse with each other in the midline & fuse with the primitive palate. Fusion of the premaxilla, palatine processes of maxilla& nasal septum begins at 8 th week
III- Stage of ossification to form Hard palate:
• The anterior ¾ of the palate ossify hard palate & posterior ¼  the soft palate & uvula.

29. DEVELOPMENTAL ANOMALIES OF THE FACE

30. DEVELOPMENT OF FACE

31. 31
A .Incomplete cleft lip .B .Bilateral cleft lip .C .Cleft lip, cleft jaw, and cleft palate .D .Isolated cleft palate .E .Oblique facial cleft .

32. 32
Ventral view of the palate, gum, lip, and nose .A .Normal .B .Unilateral cleft lip extending into the nose .C .Unilateral cleft involving the lip and jaw and extending to the incisive foramen .D .Bilateral cleft involving the lip and jaw .E .
Isolated cleft palate .F .Cleft palate combined with unilateral anterior cleft lip .

33. INCIDENCE
Cleft lip is common among males while cleft palate is more common among females.
Unilateral clefts - 80% of the incidence
Bilateral clefts - remaining 20%.

36. CLEFT LIP AND PALATE

37. CLEFT LIP AND PALATE :-
Cleft palate - A congenital fissure in the roof of the mouth, resulting from incomplete fusion of the palate during embryonic development.
Cleft lip - A congenital deformity characterized by a vertical cleft or pair of clefts in the upper lip, with or without involvement of the palate. Defective fusion of the medial nasal process with the maxillary process leads to cleft lip
GENETIC OR ENVIRONMENTAL

38. SUMMARY OF CONGENITAL ANOMALIES OF THE PALATE: (VEAU’S CLASSIFICATION)
Most accepted.
GROUP I:- cleft of the soft palate only.
GROUP II:-Cleft of the hard and soft palate to the incisive foramen.
GROUP III:-Complete unilateral cleft of the soft and hard palate, and the lip and alveolar ridge on one side.
GROUP IV:-Complete bilateral cleft of the soft and hard palate, and the lip and alveolar ridge on both sides.

39. SUMMARY OF CONGENITAL ANOMALIES OF THE FACE:
1-Oblique facial cleft:
- cleft extends from the upper lip to orbit
- Due to failure of fusion between maxillary process and lateral margin of frontonasal process
2- Cleft upper lip ( hare lip): Involve upper lip cleft with or without cleft palate (medial nasal process)
-Median hare lip: partial or complete failure of fusion of the two medial nasal processes to form the intermaxillary segment (absent phitrum)
- Unilateral hare lip: failure of fusion of maxillary process with intermaxillary processes ( the medial nasal process) on one side
-Bilateral hare lip: failure of fusion of maxillary processes with intermaxillary processes (the medial nasal processes) of both sides
3- Median cleft lower lip:
- Due to failure of fusion between the 2 mandibular processes.

40. 4- Macrostomia (larg mouth):
Due to arrest of fusion between the maxillary and mandibular processes to shift the angle medially >>> very big oral fissure.
5- Microstomia:
Due to excessive fusion between the maxillary and mandibular processes >>>>very small oral fissure.
6- Aganthia: absent lower jaw
7- Micrganthia: small lower jaw
8- Atresia of nasolacrimal duct: failure of the canalization of the nasolacrimal duct
9. Congenital anomalies of the nose:
1.Absent Nose: No nasal processes are formed
2.Single nostril: Only one nasal Placode is formed
3.Stenosis (Narrowing) of the nostril
4.Deviation of the Nasal Septum
5.Bifid nose: if the medial nasal processes do not merge completely
SUMMARY OF CONGENITAL ANOMALIES OF THE FACE:

41. DEVELOPMENT OF EAR
• Ear consists of 3 anatomical parts:
- Internal ear
- Middle ear
- External ear
-External ear:
External acoustic meatus:-
Develops by deepening of the dorsal end of the 1st pharyngeal groove.
• Pinna or Auricle:
Six mesenchymal hillocks – Auricular hillocks develop from the 1st and 2nd pharyngeal arch.

42. DEVELOPMENT OF EAR
-Middle ear:
Develops from the tubotympanic recess i.e. derived from the 1st pharyngeal pouch.
Tympanic cavity- Distal portion of the tubotympanic recess expands.
-Tympanic membrane: Ectodermal lining from1 ST pharyngeal groove
-Mesodermal lining from 1st and 2nd arch
-Endodermal lining from tubotympanic recess

43. DEVELOPMENT OF EAR
Ear ossicles:
• 1st bone to attain ultimate size.
• Maleus and Incus develop from the 1st arch.
• Stapes develop from 2nd arch.
• Ossification begins in the 16th week and continues up to the 25th week
-INTERNAL EAR:
• OTIC PLACODE

44. DEVELOPMENT OF EAR

45. DEVELOPMENT OF EYE
• Eyes develop from three sources:
Neuroectoderm of the forebrain: - retina, optic nerve.
Surface ectoderm of the head:- lens
Mesoderm between these layers - eye muscle and vascular tissues
• 1st indication of eye formation is optic sulcus which is formed in the 4th week.

46. DEVELOPMENT OF EYE

47. DEVELOPMENT OF TEETH
• The teeth are formed in relation to the dental lamina. An enlargement of dental lamina for each tooth is formed which is called the enamel organ. Ameloblasts form the enamel, odontoblasts form the dentine and the mesenchyme that invaginates into enamel organ forms the pulp.
• The ant. 2/3rd of the tongue is formed from the lingual swellings and the tuberculum impar.
• The post.1/3rd of the tongue is formed by cranial part of hypobranchial eminence.
• The salivary glands develop as outgrowths of buccal epithelium.
• The palatine tonsil develops in relation to 2nd pharyngeal pouch.

48. Anodontia
Oligodontia
Microdontia/macrodontia
Gemination Concrescence FUSION
Fusion
Dilaceration
Supernumerary teeth
Amelogenesis imperfecta SUPERNUMERARY
Enviornmental enamel hypoplasia
DEVELOPMENTAL DEFECTS OF TEETH

49. DENTAL PROBLEMS:-
Congenitally missing teeth (most commonly the upper laterals)
Presence of natal or neonatal teeth
Presence of supernumerary teeth
Ectopically erupting teeth
Anomalies of tooth morphology
Enamel hypoplasia

50. Microdontia
Fused teeth
Macrodontia
Mobile and early shedding of teeth due to poor periodontal support
Posterior and anterior cross bite
Protruding premaxilla
Deep bite
Spacingcrowding
DENTAL PROBLEMS:-

51. Third week
Development of ear
Formation of Stomatodaeum.
Fourth week
Formation of Fronto-nasal process, maxillary and mandibular process.
Development of cranial base.
Formation of pharyngeal arches.
Development of tongue.
Fifth week
Formation of Nasal placode, Medial and lateral nasal process.
Development of mandible.
Sixth week
Development of Nasal cavity.
Development of Parotid and Submandibular salivary glands
Seventh week
Formation of pre-maxilla
Eight week
Formation of definitive palate.
Development of Sublingual salivary glands
Tenth week
Development of TMJ
Development of Maxillary sinus.
Twelth week
Development of Ethmoidal, Frontal and Sphenoidal sinuses.

52. I. GIVE AN ACCOUNT ON:
1. Development of the face
2. Development of the Palate
3. Development of the Nose
4. Congenital anomalies of the face& its causes
5. Congenital anomalies of the Palate& lip & its causes
6. Innervation of the face from Embryological background

53. II. COMPLETE THE FOLLOWING STATEMENTS
1.A Furrow called…………forms between maxillary and lateral nasal prominence
2.Nasolacrimal groove gives rise to ……… and ………Most of the face originates from …..…and ….… type of cells
3.The ……… and ….….. pharyngeal arches are responsible about the development of the face
4.Early structures that form the face appear at the……… week
5.At 10 weeks, in the face the …………… develop from mandibular prominence?
6.At 10 weeks, what structures arise from Medial nasal prominence
1. ……………………………..
2………………………………..
8. The primitive palate is formed from ………..process; While the secondary palate is formed from ……. process

54. III. MCQ
1. The palatine processes begin to fuse at:
A.six weeks post-fertilization.
B.eight weeks post-fertilization.
C.ten weeks post-fertilization.
D.twelve weeks post-fertilization. 2. Complete bilateral cleft palate is due to failure of fusion of the:
A. palatine processes.
B. palatine and frontonasal processes.
C. palatine, frontonasal and secondary nasal processes.
D. palatine, frontonasal, secondary nasal processes and mandibular processes.

55. THANKS