7/28/2019 Head and Neck Dev 08
1/71
Embryology of the Head,Face and Oral Cavity
Raj Gopalakrishnan B.D.S., Ph.D.Oral and Maxillofacial Pathology
Dept. of Diagnostic and Biological Sciences
University of Minnesota School of Dentistry
7/28/2019 Head and Neck Dev 08
2/71
Prenatal Development
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
3/71
Differentiation of the Morula into Blastocyst
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition
7/28/2019 Head and Neck Dev 08
4/71
Formation of Two-Layered Embryo (2nd week of gestation)
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
Called bilaminar germ disk
Ectoderm
EndodermPre/prochordal plateFirm union between ectodermal and
endodermal cells occur at prechordal
plate
7/28/2019 Head and Neck Dev 08
5/71
Formation of Three-Layered Embryo: Gastrulation (3rd week)
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Triploblastic embryo
7/28/2019 Head and Neck Dev 08
6/71
Formation of Three-Layered Embryo: Gastrulation (3rd week)
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
7/71
First 3 weeks: Leads to formation of triploblastic embryo
Next 3-4 weeks: differentiation of major tissues and organs
includes head and face and tissues responsible
for teeth development
differentiation of nervous tissue from ectoderm
differentiation of neural crest cells (ectoderm)
differentiation of mesoderm
folding of the embryo (2 planes-rostrocaudal and lateral)
7/28/2019 Head and Neck Dev 08
8/71
Neural tube undergoes massive expansion to form the forebrain,
midbrain and hindbrain
Formation of neural tube and neural groove
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
Neural groove
7/28/2019 Head and Neck Dev 08
9/71
Components of the mesoderm
Along the trunk paraxial mesoderm breaks up into segmented
blocks called somites
Each somite has: sclerotome- 2 adjacent vertebrae and disks
myotome-muscle
dermatome-connective tissue of the skin over the somite
In the head region the paraxial mesoderm only partially fragments to form a series
of numbered somatomeres which contribute to head and neck musculature
Intermediate mesoderm: urogenital system
Lateral plate mesoderm: connective tissue of muscle annd viscera; serous
membranes of the pleura; pericardium and peritoneum; blood and lymphatic cells;
cardiovascular and lympahtic systems, spleen and adrenal cortex.Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
10/71
In the head, the neural tube undergoes massive expansion to form
the forebrain, midbrain and hindbrain
The hindbrain segments into series of eight bulges called
rhombomeres which play an important role in development of the head
7/28/2019 Head and Neck Dev 08
11/71
Folding of the Embryo
Head fold forms a primitive
stomatodeum or oral cavity; leading
to ectoderm lining the stomatodeum
and the stomatodeum separated from
the gut by buccopharyngeal membrane
Onset of folding is at 24 days and
continues till the end of week 4
Embryo just before folding (21 days)
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
12/71Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition
7/28/2019 Head and Neck Dev 08
13/71
Neural Crest Cells
Group of cells separate from the neuroectoderm, migrate and
differentiate extensively leading to formation of cranial sensoryganglia and most of the connective tissue of the head
Embryonic connective tissue elsewhere is derived form mesoderm
and is known as mesenchyme
But in the head it is known as ectomesenchyme because of its
origin from neuroectoderm
Look up Fig 2-12 in text book for derivative of the germ layers
and neural crest
7/28/2019 Head and Neck Dev 08
14/71Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Avian neural crest cells
7/28/2019 Head and Neck Dev 08
15/71
Head Formation
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Rhombomeres
(one of the first are the
occipital somites)
7/28/2019 Head and Neck Dev 08
16/71
Neural Crest Cell Migration
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
17/71
Pharyngeal arches expand by proliferation of
neural crest cells
Couly et al., 2002
Forebrain(prosencephalon)
Midbrain
(mesencephalon)
Hindbrain
(rhombencephalon)
r3
r5
7/28/2019 Head and Neck Dev 08
18/71
Migration of cranial neural crest cellsAnterior midbrain
Posterior midbrain
Anterior hindbrain
Imai et al., 1996
E
E
E
FNM
TG
TG
TG
Md
Md
7/28/2019 Head and Neck Dev 08
19/71
Clinical Correlation
Treacher Collins Syndrome is characterized by defects of
structures that are derived form the 1st and 2nd branchial arches andis due to failure of neural crest cells to migrate properly to the
facial region
7/28/2019 Head and Neck Dev 08
20/71
Sagittal section through a 25-day embryoFigure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Buccopharyngeal membrane ruptures at 24 to 26 days
7/28/2019 Head and Neck Dev 08
21/71
Internal View of the Oral Pit at 3.5 weeks
7/28/2019 Head and Neck Dev 08
22/71
26-day embryo
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Th h l t
7/28/2019 Head and Neck Dev 08
23/71
The Developing Human by Moore & Persaud
groove/cleft
pouch
arch
membrane
esophagus
The pharyngeal apparatus
1 234
Branchial arches form in the pharyngeal wall (which has lateral plate mesoderm sandwiched
between ectoderm and endoderm) as a result of lateral plate mesoderm proliferation and
subsequent migration by neural crest cells
7/28/2019 Head and Neck Dev 08
24/71
3 weeks
7/28/2019 Head and Neck Dev 08
25/71
Sagittal view of the branchial arches with corresponding grooves between each arch.
Pharyngeal pouches are seen in the wall of the pharynx. The aortic arch vasculature
leads from the heart dorsally through the arches to the face
7/28/2019 Head and Neck Dev 08
26/71
Fate of the Pharyngeal Grooves and Pouches
First groove and pouch: external auditory meatus
tympanic membrane
tympanic antrum
mastoid antrum
pharyngotympanic or eustachian tube
2nd, 3rd and 4th grooves are obliterated by overgrowth of the secondarch forming a cervical sinusif persists forms the branchial fistula
that opens into the side of the neck extending form the tonsillar sinus
2nd
pouch is obliterated by development of palatine tonsil
3rd pouch: dorsally forms inferior parathyroid gland
ventrally forms the thymus gland by fusing with the
counterpart from opposite side
7/28/2019 Head and Neck Dev 08
27/71
4th pouch: dorsal gives rise to the superior parathyroid gland
ventral gives rise to the ultimobranchial body (which
gives rise to the parafollicular cells of the thyroid gland)
5th pouch in humans is incorporated with the 4th pouch
7/28/2019 Head and Neck Dev 08
28/71
(A) Tissue from arch II and V growing towards each other (arrows) to make branchial
arches and grooves disappear
(B) Resulting appearance following overgrowth
(C) Contribution of each pharyngeal pouch
7/28/2019 Head and Neck Dev 08
29/71
Anatomy of the Branchial Arches
Cartilage of 1starch: Meckels
Cartilage of 2nd
arch: ReichertsOther arches not named
Some mesenchyme around cartilage
gives rise to striated muscle
Each arch also has an artery and nerve
Nerve: two components (motor and
sensory)
Sensory nerve divides into 2 branches:
1. Posttrematic branch: covers the anteriorhalf of the arch epithelium
2. Prettrematic: covers the posterior half
of the arch epithelium
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
30/71
Meckels cartilage: Has a close relationship with the
developing mandible BUT DOES NOT CONTRIBUTE TO IT
Indicates the position of the future mandible.
The mandible develops by intramembranous ossification.The malleus and the incus develop by endochondral ossification of
the dorsal aspect of this cartilage.
Innervation: V cranial nerve
Reicherts: Dorsal end: stapes and styloid process
Ventral end: lesser horns of hyoid bone and superior
part of the body of the hyoid bone
Innervation: VII cranial nerve
Cartilage of the 3rd arch: inferior part of the body and greater
horns of the hyoid bone
Cartilage of 4
th
and 6
th
arches: fuse to form the laryngeal cartilage
7/28/2019 Head and Neck Dev 08
31/71
Table obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
32/71
Aortic Vasculature Development
(A) At 4 weeks the anterior vessels have passed through each branchial arch tissue
and have disappeared. The pouches project laterally between each arch.
(B) At 5 weeks the 3rd branchial arch vessel becomes the common carotid, which
supplies the face by means of the internal carotid and stapedial arteries.
Face, Neck and Brain are supplied by the common carotid through internal carotid.
But by 7 weeks the circulation of face and neck shifts from the internal carotid to
external carotid. The internal carotid continues to supply the brain.
7/28/2019 Head and Neck Dev 08
33/71
Details of the aortic arch changes during early development. Aortic arch vessels numbers
1,2 and 5 disappear . Arch 3 becomes the common carotid artery. Arch 4 becomes the
dorsal aorta and enlarges so that the common carotid arises from the aorta. Arch 6 becomes
the right and left pulmonary arteries
7/28/2019 Head and Neck Dev 08
34/71
Shift in the vascular supply to the face
(A)Face and brain are supplied first by the internal carotid artery
(B) Facial vessels detach from the internal carotid and attach to the
external carotid
7/28/2019 Head and Neck Dev 08
35/71
Muscle cells in the first arch become apparent
during the 5th week and begin to spread within
the mandibular arch into each muscle sitesorigin in the 6th and 7th week. These form the
muscles of masticationmasseter, medial
pterygoid, lateral pterygoid and temporalis
muscle. They all relate to the developing mandible
By 7 weeks the muscles of 2nd arch growupward to form the muscles of face.
As these muscles grow and expand they
forms sheet over the face and forms the
muscles of facial expression
7/28/2019 Head and Neck Dev 08
36/71
Facial muscles grow from
the 2nd branchial arch to cover
the face, scalp and posterior
to the ear
Masticatory muscles of the mandibular arch
7/28/2019 Head and Neck Dev 08
37/71
Cranial Nerves growing into Branchial Arches
7/28/2019 Head and Neck Dev 08
38/71
Cartilages derived from the
branchial arches
Arch 1: Meckels cartilage and incus
Arch 2: Stapes, stylohyoid and lesser
hyoid
Arch 3: Greater hyoid
Arch 4 and 6 thyroid and
laryngeal cartilage
7/28/2019 Head and Neck Dev 08
39/71
Congenital auricular sinuses and cysts
Branchial cysts
Branchial sinuses
Branchial fistula
Branchial vestiges(cartilaginous or bony remnants)
Branchial cysts
Anomalies of the head and neck
Dermatlas
Dermatlas
7/28/2019 Head and Neck Dev 08
40/71
Apparent fusion of facial processes by
elimination of furrowsTrue fusion of facial processes by
breakdown of surface epithelium
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Development of the Face
7/28/2019 Head and Neck Dev 08
41/71
Development of the Face
The face develops between the 24th and 38th days of gestation
On 24th day, the 1st branchial arch divides into maxillary and
mandibular arches
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
42/71
Frontonasal process
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
43/71
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
44/71
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
45/71
Middle portion of the upper lip: Formed by the fusion of the medial
nasal process of both sides along with the frontonasal process
Lateral portion of the upper lip: Fusion of the maxillary processes
of each side and medial nasal process
Lower lip: Formed by the fusion of the two mandibular processes
Formation of the Lips
Unusual fusion between maxillary process and lateral nasal process
leading to canalization and formation of the nasolacrimal duct
7/28/2019 Head and Neck Dev 08
46/71
Human embryo at 7 weeks
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition
Cleft Lip
7/28/2019 Head and Neck Dev 08
47/71
Cleft Lip
7/28/2019 Head and Neck Dev 08
48/71
7/28/2019 Head and Neck Dev 08
49/71
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
50/71
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
51/71
Derivation and Terminology of the Pituitary Gland
Oral Ectoderm Adenohypophysis Pars distalis
(hypophysial diverticulum (glandular portion) Pars tuberalis
from roof of stomodeum) Pars intermedia
Neuroectoderm Neurohypophysis Pars nervosa(neurohypophysial (nervous portion) Infundibular stem
diverticulum from Median eminence
floor of diencephalon)
Clinical Significance: Craniopharyngiomas develop from remnants
of stalk of hypophysial diverticulum (in pharynx of sphenoid bone)
7/28/2019 Head and Neck Dev 08
52/71
Formation of the palate (weeks 7 to 9)
Palate develops from the primary palate and the secondary palate
The primary palate develops at about 28 days of gestation
Primary palate develops from the frontonasal and medial nasal
processes and eventually forms the premaxillary portion of the maxilla
The secondary palate develops between 7th and 8th week of gestation
and completes in the 3rd month
The critical period of palate development is from the end of 6th
weektill the beginning of 9th week
Formation of the secondary palate
7/28/2019 Head and Neck Dev 08
53/71
Formation of the secondary palate(starts between 7 to 8 weeks and completed around 3 months)
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
54/71
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
Cleft Palate
7/28/2019 Head and Neck Dev 08
55/71
Cleft Palate
Formation of the Tongue
7/28/2019 Head and Neck Dev 08
56/71
Formation of the Tongue
The tongue begins to develop at about 4 weeks. The oral part (anterior
two-thirds) develops from two distal tongue buds (lateral lingual
swellings) and a median tongue bud (tuberculum impar) [1st branchialarch].
Innervation: V nerve
The pharyngeal part develops from the copula and the hypobranchial
eminence [2nd, 3rd and 4th branchial arches].Innervation: IX cranial nerve
The line of fusion of the oral and pharyngeal parts of the tongue is
roughly indicated in the adult by a V-shaped line called the terminal
sulcus.
At the apex of the terminal sulcus is the foramen cecum.
Muscles of the tongue develop form the occipital somites and
innervated by hypoglossal nerve
7/28/2019 Head and Neck Dev 08
57/71
Lingual swelling
Tuberculum impar
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
58/71
7/28/2019 Head and Neck Dev 08
59/71
The lingual papillae appear by the end of 8th week
Vallate and foliate papillae appear first, fungiform andfiliform (10-11 weeks) papillae appear later
Taste buds develop during the 11 to 13 weeks by inductive
interaction between epithelial cells of the tongue and invadinggustatory nerve cells from chorda tympani, glossopharyngeal
and vagus nerves
7/28/2019 Head and Neck Dev 08
60/71
Thyroid gland development (4 to 7 weeks)
Figures obtained from Before We Were Born; Moore and Persaud, 6thedition, 2003.
7/28/2019 Head and Neck Dev 08
61/71
Thyroglossal duct cyst
Lingual thyroid
7/28/2019 Head and Neck Dev 08
62/71
Development of Jaw Bones
7/28/2019 Head and Neck Dev 08
63/71
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition
Development of Jaw Bones
Development of Mandible
7/28/2019 Head and Neck Dev 08
64/71
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
p
7/28/2019 Head and Neck Dev 08
65/71
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
66/71
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
67/71
Fate of Meckels Cartilage
Posteriormalleus of the inner ear
Sphenomandibular ligament
Anteriorly, may contribute to mandible
by endochondral ossification (some evidence)
Rest are resorbed completely
S d C til
7/28/2019 Head and Neck Dev 08
68/71
Three secondary (growth) cartilages govern further growth of
mandible until birth
1. Condylar cartilage (most important)
2. Coronoid cartilage
3. Symphysial cartilage
Secondary Cartilages
7/28/2019 Head and Neck Dev 08
69/71
Appears during 12th week and occupies most
of the ramus and is quickly ossified by
endochondral ossification, with a very thin
layer of cartilage present in the condylar head.This remnant persists until 2nd decade of life
and is important for growth of mandible
Appears at 4 months and
disappears immediately
Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6 th edition
7/28/2019 Head and Neck Dev 08
70/71
Development of Maxilla
Develops from one center of ossification in maxillary process of
the 1st branchial arch
Center of ossification is angle between the divisions where the
anterosuperior dental nerve is given off from inferior orbital nerve
from where it spreads posteriorly, anteriorly and superiorly
No arch cartilage is present, so maxilla develops in close
association with the nasal cartilage
One secondary cartilage also contributes to maxilla
development: zygomatic cartilage
7/28/2019 Head and Neck Dev 08
71/71