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Questions
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Answer
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The
cartilaginous capsules in the cephalic region are |
Nasal,
olfactory and optic. They function to protect the sense organ during the formative stage. |
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The
nasal, olfactory and optic cartilaginous capsules comprises the |
Neurocranium
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The
branchial cartilage system also includes |
Trabecular
cartilage. It is the cartilage 0. This has migrated to support the neurocranium. |
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Chondrocranium
is made up of |
Neurocranium
and viscerocranium |
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The
early chondrocranium can be visualized in the |
12th
week of Intrauterine life. A well developed chondrocranium can be visualized only when the bone and cartilages are formed, which occur after 10th week of intrauterine life. |
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Neural
tube is produced by the formation and fusion of |
Neural
fold. The nervous system develops as a thickening within the ectodermal layer at rostral end (neural plate) that forms the raised margins (neural folds). In this a midline depression (neural groove) is formed. The neural fold folds itself so that a tube is formed. |
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The
paraxial mesoderm is situated ___________ to the neural tube |
Lateral.
The mesoderm first thickens on each side of midline to form the paraxial mesoderm. They latter break up to form somites. |
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The
first somite is the |
Occipital.
Each somite has a sclerotome (that forms 2 adjacent vertebrae), a myotome (that gives rise to muscles) and a dermatome. |
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The
neural crest cell arises from |
Mid
brain and two rhombomeres |
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“HOX” family of homeobox genes are not
expressed |
Anterior
to rhombomere 3 |
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Migratory
pathway of neural crest cells are formed by the expression of the |
Tenascin
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Anterior
to rhombomere 3, the gene (s) expressed is / are |
MSX
gene; DLX gene; Bar gene |
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Some
derivatives from the first pharyngeal groove and pouch |
External
auditory meatus; Tymphanic membrane and antrum; Pharyngotympanic tube and mastoid antrum |
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The
third pharyngeal pouch give rise to the |
Inferior
parathyroid gland and thymus. Superior parathyroid gland derives from the dorsal part of the 4th pharyngeal pouch, Thyroid glands (parafollicular cells) from the ventral part of the 4th pharyngeal pouch, Inferior parathyroid gland from dorsal part of 3rd pharyngeal pouch and thymus from ventral part of 3rd pharyngeal pouch. |
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The
inner aspect of first branchial arch is lined by the |
Ectoderm
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The
inner aspect of the hyoid arch is lined by the |
Endoderm.
So is in all other pharyngeal arches (Except the first). |
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The
maxillary process is formed at about |
24th
day of Intrauterine life |
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The
olfactory placodes develop at the |
28th
day of Intrauterine life |
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The
face develops between |
24th
to 38th day of Intrauterine life |
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In
the 4th – 5th week of human embryo, the depression between the two nasal processes is the |
Frontonasal
process |
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The
epithelium in the groove of the furrow separating the maxillary and lateral nasal process forms the |
Nasolacrimal
duct |
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At
the 37th day of intrauterine life the human embryo shows odontogenic epithelium can be visualized as the parts of the primary epithelial band in |
Inferior
border of maxillary process; Superior border of mandibular arch; Lateral aspect of medial nasal process. The primary epithelial band is an arch shaped continuous plate of odontogenic epithelium that forms from 4 separate zones of epithelial proliferation, the middle two associated with medial nasal process in the upper arch and two zones in lower arch –one in each process. |
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Primary
palate is formed by the fusion of |
Frontonasal
and medial nasal process |
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The
secondary palate is initiated at the |
7th
to 8th week of Intrauterine life |
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Secondary
palate is formed by the fusion of |
Lateral
nasal processes |
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The
movement of tongue from its place of formation to its place of function is during the |
7th
to 8th week of Intrauterine life. This happens before the secondary palate formation begins. As the tongue is withdrawn below the processes starts to move towards each other and downwards, merging at the midline. |
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During
palate formation, the cause of secondary palate closure is due to |
Increased
glycosaminoglycans attract water casing turgidity; contractile fibroblasts in the shelves; Displacement of tongue. The intrinsic force that makes this event is not determined. The above mentioned are suggested possibilities. |
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For
the fusion of palatine shelves to occur the epithelium covering the palatine shelves should be eliminated. This is accomplished by the |
Transformation
of epithelial cells to mesenchymal like cells; Migration of epithelium to the surfaces; Apoptosis of epithelium occurs. It is found out that once 2 shelves meet; there is a cessation of DNA synthesis and the carbohydrate rich coat permits adhesion. The events that follow are not clear. The choices mentioned are described by various research groups. |
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Initial
development of human tongue is observed during |
4th
week |
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Tuberculum
impair and lateral lingual swelling are associated with |
Mandibular
process; Anterior two third of tongue; First brachial arch. They merge with each other to form a large mass from which the mucous membrane covering the anterior two third of tongue is formed. |
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Root
of tongue arises from |
Hypobranchial
eminence. It is a large midline swelling developed from mesenchyme of third arch, which rapidly divides and overgrows the 2nd arch suppressing its contribution to further tongue development. It forms the mucous membrane covering the posterior one third of tongue is formed. |
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Anterior
copula of the third pharyngeal arch gives rise to |
Mucosa
of root of tongue |
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The
lingual sulcus is created by the |
Downward
growth of ectoderm and degeneration. This forms the lingual sulcus and gives the tongue its mobility space. |
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Muscle
of tongue arises from |
Occipital
somite |
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The
innervation of tongue is |
Trigeminal
nerve; Facial nerve; Hypoglossal nerve. This is due to the unusual development pattern of tongue. Mucosa of anterior two third is supplied by trigeminal nerve (5th cranial nerve). Mucosa of posterior one third is supplied by glossopharyngeal nerve (9th cranial nerve). Motor supply is via the hypoglossal nerve (12th cranial nerve). |
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The
secondary growth cartilage of mandible is (are) |
Condylar
cartilage; Coronoid cartilage; Symphyseal cartilage |
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The
condylar cartilage remains active from |
12th
to 20th week of intrauterine life. When active it is a cone or carrot shaped structure. |
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The
remnants of condylar cartilage remain till |
Life
time |
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The
coronoid cartilage persist till only |
4th
month of intrauterine life |
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The
centre of ossification of maxilla is closely associated with the cartilage of |
Nasal
capsule |
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The
ossification of mandible begins at |
7th
week |
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The
initial ossification of mandible begins at the |
Angle
of division of inferior alveolar and mental nerves |
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Rudimentary
human mandible can be appreciated at the |
10th
week |
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The
turning of ossification in to mesenchyme away from Meckel’s cartilage is marked by the |
Lingula
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The
secondary growth cartilage of maxilla is the |
Malar
cartilage |
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The
dental lamina makes its presence in the human embryo at about |
42nd
to 48th day of Intrauterine life. 55 -56th day – bud stage for deciduous teeth, 14th week – bell stage for deciduous teeth, bud for permanent teeth, 18th week – dentin and functional ameloblasts in deciduous teeth, 32nd week – dentin and functional ameloblasts of some permanent teeth. |
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Odontogenesis
is a process that is first initiated by factors resident in the |
First
arch epithelium |
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Odontogenesis
in latter stages is maintained by factors resident in the |
First arch ectomesenchyme
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Specific
and transient expression of ___________gene are observed at potential sites of teeth formation along the laminar epithelium |
BMP-
2, 4 |
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Specific
and transient expression of ___________gene are observed at potential sites of teeth formation along the ectomesencyme |
BMP4,
MSX1, 2 |
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A
process by which a during development a mass of cells transforms itself in to morphologically and functionally distinct component is termed as |
Histodifferentiation
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In
bell stage of odontogenesis increased alkaline phosphatase activity is demonstrated in |
Stratum
intermedium. Inner dental epithelium demonstrates high quantities of glycogen that is essential for its normal function and will be greater demand once the first layer of dentin is formed. |
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Dental
lamina usually breaks/ disintegrates up during the |
Bell
stage |
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Shape
of future crown of the tooth is determined at the |
Bell
stage |
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During
bell stage of tooth development, shape of crown is determined by cessation of mitotic division occurs at |
Inner
dental epithelium |
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The
point at which the ameloblasts first differentiates represent the |
Tip
of growth center |
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Crown
pattern is determined by the differential cell division of the |
Inner
dental epithelium |
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The
crown pattern in a human child include |
Incisiform;
Caniniform; Molariform |
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The
theory that proposes that the factors responsible for tooth shape are resident in ectomesenchyme and in distinct and graded fields is the |
Field
model theory |
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The
homeobox genes expression involved in the formation of an incisor are |
MSX
1,2 |
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The
homeobox genes expression involved in the formation of a canine are |
MSX1,2,
DLX2 |
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The
homeobox genes expression involved in the formation of a molariform tooth are |
BARX
1, DLX2 |
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The
theory that supposes that a tooth class is derived from a clone of ectomesenchymal cells programmed by epithelium to produce a teeth of a given pattern is the |
Clone
model theory |
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The
nerve penetrates the dental papilla after |
Dentinogenesis.
Pioneer nerve fibers approach developing tooth during bud stage and form a plexus around the follicle and penetrate the dental papilla only after the dentinogenesis. |
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Initiation
of primary teeth formation occurs during |
6th
to 8th week of Intrauterine life |
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Initiation
of successional teeth formation occurs during |
20th
week of Intrauterine life to 10 months |
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Initiation
of non-successional permanent teeth formation occurs during |
20th
week of Intrauterine life to 5th year |
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Functional
ameloblasts of permanent first molars of humans can be observed by |
32nd
week of Intrauterine life |
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The
gene responsible for most of amelogenin secretion is located in the |
X
chromosome – Xp22.1-Xp22.3 minor in Y chromosome |
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The
gene responsible for most of tuftelin secretion is located in the |
Y
chromosome |
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Complete
salivary gland development is achieved in the presence of |
First
arch ectomesenchyme |
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The
site of bud clefting during salivary gland formation is determined by the |
Contraction
microfilaments of epithelial cells |
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A
sympathetic innervation of the developing salivary gland is essential for |
Acinar
differentiation |
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A
parasympathetic innervation of the developing salivary gland is essential for |
Whole
salivary gland differentiation |
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The
parotid salivary glands are formed in the |
4th
to 6th week of Intrauterine life |
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The
teeth constitute approximately how much of the surface area of the whole mouth |
They
occupy about 21.1% of the whole mouth, with upper teeth measuring about 24 cm2 and lower teeth 20 cm2. The palate occupies 9.4%, alveolar mucosa 21.7%, vestibular mucosa 23.4%, ventral surface of tongue and floor of mouth 12.3% and dorsal tongue 12%. |
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Dentin
and pulp are similar in |
Embryological
development; Histology; Function. Based on the all features dentin arises from pulp which also provides nutrition, protects and repairs dentin. Hence this unit is better called as dentin- pulp complex. |
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The
sense of discrimination observed in tissues of oral cavity is provided by the sensory receptors in |
Periodontal
ligament. Enamel and cementum has no innervations. This sense is partly attributed to the periodontal ligament fibers. |
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The
structure (s) that perforate epithelium is (are) |
Teeth.
This is a unique feature of oral mucosa. All other structure has epithelial invaginations with no break in continuity. But in case of teeth there is a break in continuity of the oral mucosa. |
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A
typical synovial joint has articular surfaces of bone covered by |
Hyaline
cartilage. A typical synovial joint is lined by hyaline cartilage. But tempromandibular joint has articular surfaces of bone covered by a fibrous layer that is an extension of periosteum. |
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Approximately
______ % of human malformations is caused by alteration in a single gene. |
10
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The
study of developmental defects is |
Teratology
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The
early phase of human embryonic phase is characterized by |
Proliferation
and migration. The first phase of embryonic stage is largely associated with proliferation and migration, while the second or last phase of embryonic phase is associated with differentiation or morphogenesis. These two phases lasts for 4 weeks each and after 8th week the embryo is referred as fetus when growth and maturation of cells predominate. |
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The
most vulnerable period of the human gestation to develop congenital defects is |
Second
or late phase of embryo. The first phase of embryonic stage is largely associated with proliferation and migration, while the second or last phase of embryonic phase is associated with differentiation or morphogenesis where there are many intricate embryologic processes. |
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The
process in which population of cell changes and establishes a new population of cells with new characteristics is |
Differentiation.
The process that initiates the differentiation is induction; the competence is that ability of the cells to respond to induction to form new set of cells. |
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The
fundamental role in patterning is played by |
Homeobox
genes. These are a similar region of 180 nucleotide base pairs in various chromosomes producing the transcription factors. The regulatory molecules of such an event are the growth factors and retinoic acids. |
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In
human orofacial embryology, growth factors behave as an |
Inductive
agent. Homeobox genes are the one that determines the patterning, Cell surface receptors bestows competency. Growth factors are the inductive agents. They can be classified as autocrine and paracrine regulatory agents. |
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The
patterning is regulated in the intra-cellular area by |
Autocrine
and paracrine growth factors are regulatory agents that act via the cell surface receptors whereas retinoic acids act with intra-cellular receptors. |
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In
human embryo, the neural crest cells differentiate from |
Lateral
aspect of the neutral plate. Though the name indicates to originate from the crest, they originate from lateral aspect of neural plate. But in avian and other lower animals they develop from the crest. |
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Most
of the connective tissue in the head is derived from |
Neural
crest cell. During the lateral folding of embryo most of the mesoderm in the cephalic end is dis-positioned. Therefore most of the connective tissue is formed by the neural crest and hence the mesoderm in head is often referred as ectomesenchyme rather than mesenchyme. Migration of neural crest cells provides the embryonic connective tissue needed for the craniofacial development. |
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The
cartilage derived from the branchial system that form the neurocranium is |
Trabecular
cartilage. Though the Reiter’s and Merkel’s cartilage belong to the branchial system, they do not form the neurocranium. Neurocranium is formed by the occipital, parachordal cartilaginous blocks along with the trabecular cartilage. This trabecular cartilage is the first cartilage (Cartilage 0) that has migrated to support the neurocranium. |
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The
number of rhombomeres formed in human hind brain during the head formation is |
Eight.
A series of eight bulges forms along the neural tube in the area of hind brain called as the rhombomeres. |
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When
the stomatodeum first forms it is delimited rostrally by neural plate and caudally by |
Cardiac
plate. The buccopharyngeal membrane separates the stomatodeum from foregut, laterally by pharyngeal arches. |
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The
branchial arches form in the |
Pharyngeal
wall. The branchial arch form in the pharyngeal wall by the result of proliferating lateral plate mesoderm and subsequent reinforcement by the neural crest cells. |
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The
cervical sinus arise from the persistence of |
Second
pharyngeal groove; Third pharyngeal groove; Fourth pharyngeal groove. The overgrowth of second pharyngeal arch normally obliterates the 2nd, 3rd and 4th pharyngeal grooves but sometimes may persists as a cervical sinus which may or may not drain outside. |
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The
second pharyngeal pouch is obliterated by the |
Developing
palatine tonsil. But a part of this pouch persists in all individuals as the tonsillar fossa or crypt. |
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The
post-trematic branch of each branchial arch is the |
Sensory
component supplying the epithelium that covers anterior half of arch. The pre-trematic branch supplies the epithelium that covers the posterior half of epithelium of the preceding arch. |
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Union
of palatal processes is best described as |
Actual
fusion of processes. Generally ostensible fusion of processes actually involves the elimination of a furrow at the site of the union. Rarely such as in this case there is a complete merging and crossing of the tissues. |
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The
floor of the mouth is formed by the epithelium covering the |
Mesenchyme
of the 1st pharyngeal arch; Mesenchyme of the 2nd pharyngeal arch ; Mesenchyme of the 3rd pharyngeal arch |
Prof. Rooban Thavarajah
Oral and Maxillofacial Pathologist
List