The document outlines the development of the face, oral cavity, nasal passage, tongue, and mandible during embryonic weeks 4 to 10. Key processes include the fusion of facial prominences, formation of the secondary palate, and the origins of the tongue and mandible. It highlights the roles of various embryonic tissues and the ossification process in shaping these structures.

1. FACE DEVELOPMENT (1)

2. •
1.
2.
3.
•
Morphology of face is developed from 5 prominences:
Frontonasal process
2 maxillary swelling
2 mandibular swelling
These process cause furrows between processes, and fusion of prominences involves
elimination of furrows.

3. • Oral cavity (primitive stomatodeum) is at first bounded:
I.
Above: frontal prominence
II. Below: developing heart
III. Laterally: first branchial arch
• With the spread of arches together, the cardiac plate is eliminated
from stomatodeum.
• Thus, epithelial covering the mesechyme of 1st, 2nd and 3rd branchial
arches forms floor of the mouth.

4. • Week 4: (position of stomatodeum)
-The stomatodeum is limited cranially by the frontal process, laterally by the maxillary
process and ventrally by the mandibular process.
• Week 5: (olfactory placode and lower lip forms)
-The frontal prominence, just rostral to the stomatodeum, form olfactory placode due
to the rapid proliferation of underlying mesenchyme.
-The ectoderm at the center of placodes invaginated to form an oral nasal pit
-This devides the raised rim of placode into lateral and medial nasal process.
-The groove between the lateral nasal process and the adjacent maxillary swelling is
called the nasolarimal groove. Later the ectoderm of this groove invaginated into the
underlying mesenchyme to form the nasolacrimal duct.
-The mandibular swellings come together and fuse to form the lower lip.

5. • Week 6: (septum and philtrum formation)
-At the beginning of week 6, the lateral part of the face expands and broadens. This causes the
eyes and maxillary process which where initially located at the side of the face to come to the
front of the face.
-The medial nasal process migrates towards each other and fuse to form the septum of the
nose.
-The inferior tips of the medial nasal process expand laterally and inferiorly and fuse to form the
intermaxillary process. The tip of the maxillary swelling grows to meet the intermaxillary process
and fuse. This gives rise to the philtrum.

6. -By the time of face development, the epithelium at the inferior border of maxillary process and
superior border of mandibular process proliferate and thickens.
-When fuse they form a single primary epithelium band, joining the upper and lower jaw.

7. Nasal passage and palate
formation (2)

8. Nasal passage:
At the end of 6th week:
-The nasal pits deepens and fuse to form a single, enlarged,
ectodermal nasal sac lying super posterior to the
intermaxillary process.
At the end of 6th week to the beginning of the 7th
week:
-The floor and the posterior wall of the nasal sac proliferate to
form the nasal fin separating the nasal sac from oral cavity.
-Vacuoles develop in the nasal fin and fuse with nasal sac, the sac
enlarges and thinning the fin to a thin membrane called the
oronasal membrane.
-oral nasal membrane separate the sac from oral cavity.
During the 7th week:
-Oronasal membrane ruptures to form an opening called primitive
choana.
-The floor of the nasal cavity (primary palate) is formed by the
Posterior extension of the Intermaxillary process.

9. Secondary palate formation (week78):
-Formation involves the fusion of:
i. Right and left maxillary processes
(palatine shelf)
ii. Median nasal process
-The median nasal process grows
downward and forward to form the nasal
septum.
-The palatine shelves, at first grows
downward to the elevated the tongue.
-As a result of the enlargement of the
mandible, the tongue drops to the floor of the
stomatodeum.
-When the tongue is moved from the growing
lateral palatine processes, the processes are
straightened to a horizontal position and
grows medially towards and fuse with
each other with primary palate to form the
secondary palate

10. -The nasal septum fuse with the upper surface of the primary and secondary palates along
the midline.
-Now nasal cavity opens into the pharynx behind the secondary palate through an opening
called the definitive choana

11. Tongue formation (3)

12. Tongue development:
• Pharyngeal arch: 1, 3, and 4
• Occipital Somite Mesoderm
Begins late of 4th week
1st arch:
-Forms a median swelling called tuberculum impar.
-A pair of lateral swellings, the distal tongue buds. The lateral swellings quickly enlarge
and merge with each other and also with median swelling and form the anterior
two-third of the tongue.
2nd arch:
-Develop a midline swelling called
copula.
5th and 6th week:
a midline swelling of the 3rd and 4th arches called
hypopharyngeal eminence overgrows the copula
which disappears. Thus, forms the posterior onethird of the tongue.
(Hypo pharyngeal eminence expand mainly by the
growth of 3rd arch endoderm.)
A depression called foramen cecum is visible where the
median and terminal sulcus intersect.

13. 4th arch:
-Marks the development of epiglottis.
-Tongue separates from the floor of the mouth by a downward growth of ectoderm
around its periphery, subsequently degenerates to form lingual sulcus and gives the
tongue mobility.

14. Muscles of the tongue:
-Different origin.
-Arise from the mesoderm of the occipital somites, which have migrated forward
into the tongue area.
-With their nerve- 12th cranial nerve Hypoglossal nerve (motor).
Nerve supply (sensory) correspond to their origin:
i. 1st arch nerve 5th cranial (trigeminal) nerve supply anterior two-third.
ii. 3rd arch nerve 9th cranial nerve (glossopharyngeal) supply the posterior
one third.

15. Mandibular formation (4)

16. Formation of mandible (week 6-10):
-Cartilage of 1st arch (meckel’s cartilage) is associated to this formation but makes no contribution
to it.
6th week: (meckel’s cartilage)
-Cartilage extend as a hyaline cartilagenous rod, surronded by fibrocellular capsule.
-The 2 cartilage (from left and right) do not meet at midline but are separated by a thin band
of mesenchyme.
-Mandibular nerve comes along 2/3
of the way along the length of cartilage.
At this point, it divides into lingual branch
(medial) and inferior alveolar branch
(lateral) which run along medial and
lateral aspect of the cartilage.
-Inferior alveolar further divides into
incisor and mental branches anteriorly.
-In the angle between incisor and mental
branch, condensation of mesenchyme
occurs.

17. 7th week:
•
First bone
-Intramembranous ossification begins in this condensation forming first bone.
-From this center, the bone spreads anteriorly to the midline and posteriorly to the point
where mandibular nerve divides.
-As it spreads anteriorly to midline, the bone forms a trough (drain) that consist of lateral and
medial plates that unite beneath the incisor nerve.
-It then comes into close approximation with similar trough formed in the adjoining
mandibular process.
-Trough is converted to a canal as bone form over the nerve , joining lateral and medial plate.
•
Backward extension of ossification
-Similar as forward but backward, it forms a
trough at the lateral aspect of meckel’s
cartilage.
-It is then converted to a canal that contains
inferior alveolar nerve.
•
Ramus of mandible
-Developed by a rapid spread of ossification
posteriorly into mesenchyme of 1st branchial
arch, turning away from the meckel’s cartilage.
-This point of diverge is marked by the lingula.

18. Fate of meckel’s cartilage:
1. Posterior extremity: Incus and malleus of inner ear.
2. Posterior extremity Sphenomalleolar ligament.
3. From sphenoid to the division of the mandibular nerve, cartilage is lost totally.
But its fibrous cellular capsule persist as the Sphenomandibular ligament.
4. From lingula forward to the division of the alveolar nerve: degrade, space
replace by new bone.
Further growth of mandible:
Three secondary growth cartilages appeared (Compare to primary cartilage):
i. Cells are larger
ii. Less intercellular matrix formed.
1. Condylar cartilage: appears during 12th week. Converted quickly to bone by
endochondral ossification.
2. Coronoid cartilage: anterior border and top of the condylar cartilage.
Disappears long before birth.
3. Symphyseal cartilage: two end of Meckel’s cartilage. Obliterated within the 1st
year after birth.

19. • Conclusion:
-Membrane bone is developed in relation to the nerve of 1st branchial arch and
entirely independent of meckel’s cartilage.
-It consist of neural, alveolar, and muscular element.
--It’s growth is assisted by development of secondary cartilage.