Oral Embryology-1

Questions	Answer
The cartilaginous capsules in the cephalic region are	Nasal, olfactory and optic. They function to protect the sense organ during the formative stage.
The nasal, olfactory and optic cartilaginous capsules comprises the	Neurocranium
The branchial cartilage system also includes	Trabecular cartilage. It is the cartilage 0. This has migrated to support the neurocranium.
Chondrocranium is made up of	Neurocranium and viscerocranium
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.
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.
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.
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.
The neural crest cell arises from	Mid brain and two rhombomeres
“HOX” family of homeobox genes are not expressed	Anterior to rhombomere 3
Migratory pathway of neural crest cells are formed by the expression of the	Tenascin
Anterior to rhombomere 3, the gene (s) expressed is / are	MSX gene; DLX gene; Bar gene
Some derivatives from the first pharyngeal groove and pouch	External auditory meatus; Tymphanic membrane and antrum; Pharyngotympanic tube and mastoid antrum
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.
The inner aspect of first branchial arch is lined by the	Ectoderm
The inner aspect of the hyoid arch is lined by the	Endoderm. So is in all other pharyngeal arches (Except the first).
The maxillary process is formed at about	24th day of Intrauterine life
The olfactory placodes develop at the	28th day of Intrauterine life
The face develops between	24th to 38th day of Intrauterine life
In the 4th – 5th week of human embryo, the depression between the two nasal processes is the	Frontonasal process
The epithelium in the groove of the furrow separating the maxillary and lateral nasal process forms the	Nasolacrimal duct
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.
Primary palate is formed by the fusion of	Frontonasal and medial nasal process
The secondary palate is initiated at the	7th to 8th week of Intrauterine life
Secondary palate is formed by the fusion of	Lateral nasal processes
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.
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.
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.
Initial development of human tongue is observed during	4th week
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.
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.
Anterior copula of the third pharyngeal arch gives rise to	Mucosa of root of tongue
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.
Muscle of tongue arises from	Occipital somite
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).
The secondary growth cartilage of mandible is (are)	Condylar cartilage; Coronoid cartilage; Symphyseal cartilage
The condylar cartilage remains active from	12th to 20th week of intrauterine life. When active it is a cone or carrot shaped structure.
The remnants of condylar cartilage remain till	Life time
The coronoid cartilage persist till only	4th month of intrauterine life
The centre of ossification of maxilla is closely associated with the cartilage of	Nasal capsule
The ossification of mandible begins at	7th week
The initial ossification of mandible begins at the	Angle of division of inferior alveolar and mental nerves
Rudimentary human mandible can be appreciated at the	10th week
The turning of ossification in to mesenchyme away from Meckel’s cartilage is marked by the	Lingula
The secondary growth cartilage of maxilla is the	Malar cartilage
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.
Odontogenesis is a process that is first initiated by factors resident in the	First arch epithelium
Odontogenesis in latter stages is maintained by factors resident in the	First arch ectomesenchyme
Specific and transient expression of ___________gene are observed at potential sites of teeth formation along the laminar epithelium	BMP- 2, 4
Specific and transient expression of ___________gene are observed at potential sites of teeth formation along the ectomesencyme	BMP4, MSX1, 2
A process by which a during development a mass of cells transforms itself in to morphologically and functionally distinct component is termed as	Histodifferentiation
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.
Dental lamina usually breaks/ disintegrates up during the	Bell stage
Shape of future crown of the tooth is determined at the	Bell stage
During bell stage of tooth development, shape of crown is determined by cessation of mitotic division occurs at	Inner dental epithelium
The point at which the ameloblasts first differentiates represent the	Tip of growth center
Crown pattern is determined by the differential cell division of the	Inner dental epithelium
The crown pattern in a human child include	Incisiform; Caniniform; Molariform
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
The homeobox genes expression involved in the formation of an incisor are	MSX 1,2
The homeobox genes expression involved in the formation of a canine are	MSX1,2, DLX2
The homeobox genes expression involved in the formation of a molariform tooth are	BARX 1, DLX2
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
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.
Initiation of primary teeth formation occurs during	6th to 8th week of Intrauterine life
Initiation of successional teeth formation occurs during	20th week of Intrauterine life to 10 months
Initiation of non-successional permanent teeth formation occurs during	20th week of Intrauterine life to 5th year
Functional ameloblasts of permanent first molars of humans can be observed by	32nd week of Intrauterine life
The gene responsible for most of amelogenin secretion is located in the	X chromosome -  Xp22.1-Xp22.3 minor in Y chromosome
The gene responsible for most of tuftelin secretion is located in the	Y chromosome
Complete salivary gland development is achieved in the presence of	First arch ectomesenchyme
The site of bud clefting during salivary gland formation is determined by the	Contraction microfilaments of epithelial cells
A sympathetic innervation of the developing salivary gland is essential for	Acinar differentiation
A parasympathetic innervation of the developing salivary gland is essential for	Whole salivary gland differentiation
The parotid salivary glands are formed in the	4th to 6th week of Intrauterine life
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%.
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.
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.
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.
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.
Approximately ______ % of human malformations is caused by alteration in a single gene.	10
The study of developmental defects is	Teratology
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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