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Growth of skull and jaws part 1

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the growth and development of skull and jaws part 1..along with clincial correlates

Growth of skull and jaws part 1

  1. 1. GROWTH AND DEVELOPMENT OF SKULL AND JAWS Dr.AUREUS DESOUZA P.G Resident Oral medicine and radiology MCODS, Mangalore
  2. 2. CONTENTS of PART 1 • Introduction. • Pre natal development of cranium. • Post natal development of cranium. • Clinical correlates. • Development of face. • Clinical correlates.
  3. 3. CONTENTS of PART 1 • Special note: neural crest cells • Clinical correlates • Conclusion • References
  4. 4. CONTENTS of PART 2 • Pre Natal development of the maxilla. • Post Natal development of maxilla. • Development of paranasal sinuses. • Clinical correlates.
  5. 5. CONTENTS of PART 2 • Pre Natal development of the mandible • Post natal development of mandible • Clinical correlates • Timeline of development
  6. 6. CONTENTS of PART 2 • Conclusion • References
  7. 7. GROWTH • Quantitative aspect of biologic development per unit of time. – Moyers • Growth refers to increase in size. – Todd
  8. 8. DEVELOPMENT
  9. 9. DEVELOPMENT Development refers to all naturally occurring progressive, unidirectional, sequential changes in the life of an individual from it’s existence as a single cell to its elaboration as a multifunctional unit terminating in death. – Moyers
  10. 10. DEVELOPMENT OF CRANIUM
  11. 11. CRANIUM NEUROCRANIUM (protective case around brain) VISCEROCRANIUM (skeleton of face) NASOMAXILLARY COMPLEX (DESMOCRANIUM) CRANIAL VAULT MANDIBLE (CHONDROCRANIUM) CRANIAL BASE
  12. 12. NEUROCRANIUM MEMBRANOUS NEURAL CREST CELLS & PARAXIAL MESODERM CARTILAGINOUS Prechordal chondrocranium NEURAL CREST CELLS Chordal chondrocranium OCCIPITAL SCLEROTOMES PARAXIAL MESODERM
  13. 13. Courtesy :langman medical embryology 11th ed
  14. 14. MEMBRANOUS NEUROCRANIUM Mesenchyme from these sources invests the brain and undergoes membranous ossification Needle like bony spicules radiate from primary ossification centre towards periphery
  15. 15. Courtesy:langman’s medical embroyology 11th ed
  16. 16. With growth during fetal and postnatal life ,membranous bones enlarge Apposition on outer surface Osteoclastic resorption from inside
  17. 17. CARTILAGINOUS NEUROCRANIUM Cartilages that lie in front of rostral limit of notochord arise from • neural crest cells forming prechordal chondrocranium Cartilages posterior to this limit arise from Occipital sclerotomes forming Chordal chondrocranium
  18. 18. Base of the skull All cartilages fuse Ossify by Endochondral ossification
  19. 19. • kjjkkjhihihk VISCEROCRANIUM MEMBRANOUS Intramembranous ossification in maxillary and mandibular prominence of first pharyngeal arch squamous temporal, maxillary, zygomatic bone,mandible CARTILAGINOUS Neural crest cells Bones and connective tissue of craniofacial structures
  20. 20. SKULL of the NEWBORN Flat bones are connected through seams of connective tissue SUTURES. Sagittal suture- neural crest cells Coronal suture- paraxial mesoderm FONTANELLES-more than two bones meet, sutures are widened.
  21. 21. Courtesy: “The developing human”, 8th ed by Keith Moore
  22. 22. Courtesy: “The developing human”, 8th ed by Keith Moore
  23. 23. ANTERIOR FONTANELLE - where two parietal and two frontal bones meet POSTERIOR FONTANELLE -where two parietal and occipital bones meet TIMINGS OF CLOSURE: ANTERIOR FONTANELLE= 18 months of age POSTERIOR FONTANELLE = 1 to 2 months of age Reference :Langman’s medical Embryology ,11th ed
  24. 24. Post Natal Development of skull
  25. 25. POST NATAL GROWTH OF CRANIAL BASE • Maxilla is attached to the cranial base by a number of sutures. • Mandible too is attached to the cranial base at the temporomandibular joint. • This growth processes occuring at the cranial base can affect the placement of maxilla and mandible.
  26. 26. • The bones forming the calvarium include the frontal, parietal, occipital, sphenoid and temporal bones. • The suture systems associated with these are the coronal, sagittal and lambdoidal sutures and a temporary metopic suture (permitting rapid transverse expansion pre nataly and post nataly).
  27. 27. • As the brain expands, the separate bones of the calvaria are displaced in an outward direction passive movement. • This primary displacement causes a tension in the sutural membranes, which respond by depositing new bone on the sutural edges. • Each separate bone thus enlarges in circumference.
  28. 28. • At the same time, there is apposition on the flat surfaces of both the ectocranial and endocranial sides increasing thickness of bone. • The arc of curvature of the whole bone decreases, and the bone becomes flatter. • Reversal of growth may occur in areas adjacent to the sutures outside/inside surface resorption can take place reduces the curvature.
  29. 29. Growth of cranial base Cranial base grows post-natally by complex interaction between the following three growth processes. • Extensive cortical drift and remodelling • Elongation at synchondrosis • Sutural growth
  30. 30. Cortical drift and remodelling • Remodelling : Process where bone deposition and resorption occur so as to bring about change in size, shape and relationship of bone • Cranium is divided into a no. of compartments by bony elevations and ridges present in the cranial base.
  31. 31. • These elevated ridges and bony partitions show bone deposition, while floor shows resorption • This helps in increasing the intracranial space to accommodate the growing brain
  32. 32. • Cranial base is perforated by the passage of a number of blood vessels and nerves communicating with the brain • The foramina that allow the passage of these nerves and blood vessels undergo drifting by bone deposition and resorption so as to constantly maintain their proper relationship with the growing brain
  33. 33. Synchondral growth • The midline part of the basicranium is characterized by the presence of synchondroses. • A number of synchondroses are operative during the fetal and early postnatal periods.
  34. 34. • Inter-sphenoidal synchondrosis fusion. • Spheno-ethmoidal synchondrosis- Juvenile/ adolescence • Spheno-occipital synchondrosis – Active: 12-15 years Fuses: 20yrs • Intra-occipital synchondrosis - Perinatal - Fuses: 3-5 years Structure of synchondrosis is like 2 epiphysial plates positioned back to back and separated by a common zone of reserve cartilage
  35. 35. • The spheno-occipital ,principal growth cartilage of the basicranium. • As with all growth cartilages associated directly with bone development, the sphenooccipital synchondrosis provides a pressure adapted bone growth mechanism. • This is because the cranial base supports the weight of the brain and face that bears down on the synchondrosis in the midline of cranial base.
  36. 36. • As endochondral bone growth occurs at the spheno-occipital synchondrosis, the sphenoid and occipital bones are moved apart. • At the same time new endochondral bone is laid down in the medullary region, and cortical bone is formed in the endosteal and periosteal regions. • Thus the sphenoid and occipital bones increase in length and width
  37. 37. • This is in contrast to the tension adapted sutural growth process of the calvaria, lateral neurocranial walls, and the endocranial fossae. • Endochondral bone growth by the spheno-occipital synchondrosis relates to primary displacement of the bones involved
  38. 38. • The sphenoid and the occipital bones become sieved apart by the primary displacement process and at the same time, new endochondral bone, is laid down by the endosteum within each bone. • The direction of spheno-occipital synchondrosis is upwards, it therefore carries the midface forward and downward
  39. 39. Sutural growth • Cranial base has a number of bones that are joined to one another by means of sutures 1. Spheno - frontal suture 2. Fronto - temporal suture 3. Spheno - ethmoid suture 4. Fronto - ethmoid suture 5. Fronto - zygomatic suture • As the brain enlarges during growth, bone formation occurs at the ends of the bone (that is at either ends of the suture)
  40. 40. • The temporal and frontal bones have fibrous attachments to the middle and anterior cranial fossae, respectively. As both bones expand, the two fossae are thus pulled away from each other, but both also being moved together in a protrusive direction.
  41. 41. • This sets up tension fields in the various frontal, temporal, sphenoidal, and ethmoidal sutures, and this presumably triggers sutural bone responses (in addition to direct basicranial remodeling ). • Both fossae are thus enlarged, and the nasomaxillary complex is carried along anteriorly with the floor of the anterior cranial fossa from which it is suspended.
  42. 42. CLINICAL CORRELATES CRANIOSYNOSTOSIS: Caused by premature closure of 1 or more sutures. Premature fusion of the synchondroses of the skull base • • • • causes underdevelopment of the middle third of the face reduced cranial base excessive vaulting of the calvaria (in some cases) anomalies such as exophthalmia, midfacial hypoplasia, and dental malocclusion.
  43. 43. CRANIOSYNOSTOSIS
  44. 44. Syndromes associated with craniosynostosis • • • • • Crouzon syndrome Apert syndrome Pfeiffer syndrome Muenke syndrome Saethre chotzen syndrome
  45. 45. Types of craniosynostosis • • • • • • Brachycephaly Plagiocephaly Oxycephaly Trigonocephaly Scaphocephaly Pansynostosis
  46. 46. Brachycephaly
  47. 47. Plagiocephaly
  48. 48. scaphocephaly
  49. 49. Trigonocephaly
  50. 50. Kleeblattschädel /clover leaf shaped skull
  51. 51. Oxycephaly
  52. 52. CRANIOSCHISIS • Greek: "kranion" skull, and "schisis” split) is a developmental birth defect in which cranial vault fails to form. • Hence brain tissue exposed to amnion degenerates resulting in ANENCEPHALY
  53. 53. ACHONDROPLASIA • Primarily affecting long bones • Other defects include a large skull(megalocephaly), • short fingers, • accentuated spinal curvature
  54. 54. THANATOPHORIC DYPLASIA • Most common lethal neonatal form • Autosomal dominant • Occurs when all of the sutures close prematurely,resulting in bone growing through anterior and sphenoid fontanelles. • Short curved femurs • Cloverleaf skull(kleeblattschadel) • relative macrocephaly • frontal bossing
  55. 55. HYPOCHONDROPLASIA • • • • • • Autosomal dominant form of dwarfism Short stature Broad, short hands and feet; Mild joint laxity Macrocephaly Skeletal features are very similar to those seen in achondroplasia but tend to be milder.
  56. 56. CROUZON SYNDROME • Results from an early closing (fusion) of several of the skull’s sutures – always including the side (coronal) sutures. • Wide head across the front • Short head from front to back • Flat-looking face due to underdeveloped cheekbones, eye sockets and lower jaw • Shallowly placed, protruding eyes that may be crossed or wide-set • Small nose with an upwardly tilted beak shape • No foot or hand defects
  57. 57. APERT SYNDROME • Apert syndrome is caused by an early closing (fusion) of the skull's side (coronal) sutures • Taller-than-usual head shape • Recessed mid-face shallowly placed, protruding eyes • Short, beak-shaped nose and feet • Symmetric syndactyly of hands • Cleft palate (may be present)
  58. 58. Pfeiffer syndrome Results from an early closing (fusion) of up to three of the skull’s sutures (coronal, lambdoid, and sometimes, sagittal). • Wide head across the front • Short head from front to back • Flat-looking face due to underdeveloped cheekbones, eye sockets, and lower jaw • Shallowly placed, protruding eyes that may be crossed or wide-set • Small nose with an upwardly tilted beak shape • Cleft palate(may be present)
  59. 59. MICROCEPHALY • Abnormality in which brain fails to grow and skull fails to expand. • Skull growth is determined by brain growth • Conditions that can cause microcephaly • Include infections, genetic disorders, and severe malnutrition. • Mental retardation
  60. 60. Microcephaly
  61. 61. Genetic conditions that cause microcephaly include: • • • • • • • Cornelia de Lange syndrome Cri du chat syndrome Down syndrome Rubinstein-Taybi syndrome Seckel syndrome Smith-Lemli-Opitz syndrome Trisomy 18 Reference: 1.A.D.A.M. Medical Encyclopedia. 2.http://www.ncbi.nlm.nih.gov/pubmedhealth /PMH0003756
  62. 62. These additional conditions may indirectly cause microcephaly: • Uncontrolled phenylketonuria (PKU) in the mother • Methylmercury poisoning • Congenital rubella • Congenital toxoplasmosis • Congenital cytomegalovirus (CMV) • Use of certain drugs during pregnancy, especially alcohol and phenytoin.
  63. 63. HOLOPROSENCEPHALY • Most common developmental defect of forebrain • Often accompanied by the failure of fetal facial midline structures to form properly. • Hence, here are usually midline facial defects (cleft lip, cleft palate, cyclopia, etc) accompanying this condition. Reference: http://medgen.genetics.utah.edu/phot ographs/pages/holoprosencephaly.htm
  64. 64. CONGENITAL HYDROCEPHALOUS • Hydrocephalus is due to a problem with the flow of the fluid that surrounds the brain.
  65. 65. • By 4th week of development ,bars of mesenchymal tissue (P.arches) separated by deep clefts(P.clefts). • A number of outpocketings (P.pouches) appear along the lateral wall of pharyngeal gut. • At the end of 4th week,centre of face is formed by stomodeum surrounded by first pair of P.arches
  66. 66. • At 42 days embryo • Differentiation of structers depends on epithelial and mesenchymal interactions
  67. 67. • Fourth week: development of a frontal prominence forms the stomatodeum • Below this is the formation of the first branchial arch • The first pair appears as surface elevations lateral to the developing pharynx • Soon other arches develop as obliquely disposed, rounded ridges on each side of the future head and neck region.
  68. 68. PHARYNGEAL APPRATUS • • • • consists of: Pharyngeal arches Pharyngeal pouches Pharyngeal grooves/clefts Pharyngeal membrane
  69. 69. PHARYNGEAL ARCHES • Also called as branchial arches. • Begin to develop in the fourth week just as neural crest cells migrate into the head and neck region. • Form in craniocaudal succession • Five pairs which are numbered 1,2,3,4 and 6. • Arch 5 either never forms in humans or forms as a short lived rudiment that regresses.
  70. 70. PHARYNGEAL ARCH COMPONENTS • Core – mesenchyme(3rd week) • -mostly replaced by neural crest cells (4th week) • Covered externally by –ectoderm • Internally by -endoderm
  71. 71. Fate of the pharyngeal arch components A typical pharyngeal arch contains: • An aortic arch, an artery that arises from the truncus arteriosus of the primordial heart • A cartilaginous rod that forms the skeleton of the arch • A muscular component that differentiates into muscles in the head and neck • A nerve that supplies the mucosa and muscles derived from the arch
  72. 72. PHARYNGEAL ARCHES The first pharyngeal arch Consists of dorsal portion- maxillary process Ventral portion- mandibular process Mesenchyme of maxillary process gives rise to • Premaxilla • Maxilla • Zygomatic bone • Part of temporal bone (through membranous ossification) Mandible is formed by membranous ossification of mesenchyme surrounding Meckel’s cartilage. The first pair of pharyngeal arches plays a major role in facial development
  73. 73. Fate of pharyngeal arches • The pharyngeal arches contribute exclusively to the formation of the face, nasal cavities, mouth, larynx, pharynx and neck • During the fifth week, the second pharyngeal arch enlarges and overgrows the third and fourth arches, forming the ectodermal depression called cervical sinus • By the end of seventh week the second to fourth pharyngeal grooves and the cervical sinus have disappeared, giving the neck a smooth contour
  74. 74. Derivatives of Pharyngeal arch cartilages • The dorsal end of first arch cartilage (Meckel cartilage) ossifies to form malleus and incus • The middle part of cartilage forms anterior ligament of malleus and sphenomandibular ligament • Ventral part of the first arch cartilages form primordium of the mandible • The cartilage disappears as mandible develops around it
  75. 75. Derivatives of pharyngeal arch cartilages • The dorsal end of second arch cartilage (Reichert cartilage) ossifies to form the stapes and styloid process of the temporal bone • The ventral end of second arch cartilage ossifies to form the lesser cornu and superior part of the body of the hyoid bone • Its perichondrium forms the stylohyoid ligament
  76. 76. Derivatives of pharyngeal arch cartilages • The third arch cartilage ossifies to form the greater cornu and the inferior part of the body of the hyoid bone • The fourth and sixth arch cartilages fuse to form the laryngeal cartilages except epiglottis which develops from hypopharyngeal eminence • The fifth pharyngeal arch is rudimentary and has no derivatives
  77. 77. Derivatives of Pharyngeal Arch Muscles • The musculature of the first pharyngeal arch forms the muscles of mastication • The second pharyngeal arch forms the stapedius, stylohyoid, posterior belly of digastric, auricular and muscles of facial expression • The third arch forms the stylopharyngeus • The fourth arch forms cricothyroid, levator veli palatini and constrictors of pharynx • Sixth pharyngeal arch forms the intrinsic muscles of the larynx
  78. 78. Derivatives of Pharyngeal Arch Nerves • Caudal two branches of Trigeminal nerve (maxillary and mandibular) supply derivatives of the first pharyngeal arch • The facial, glossopharyngeal and vagus nerves supply the second, third and caudal (fourth to sixth) arches respectively • The fourth arch is supplied by superior laryngeal branch of vagus nerve • The sixth arch is supplied by its recurrent laryngeal branch
  79. 79. Pharyngeal Pouches • The primordial pharynx, derived from the foregut, widens cranially where it joins the primordial mouth or stomodeum • It narrows caudally where it joins the esophagus • The endoderm of the pharynx lines the internal aspects of pharyngeal arches and passes into balloonlike diverticula called pharyngeal pouches
  80. 80. • The endoderm of the pouches contacts the ectoderm of the pharyngeal grooves and together they form the double layered pharyngeal membranes that separate the pharyngeal pouches from the pharyngeal grooves
  81. 81. Derivatives of First Pharyngeal Pouch • The first pharyngeal pouch expands into an elongate tubotympanic recess • The expanded distal part of this recess contacts the first pharyngeal groove, where it contributes to the formation of the tympanic membrane (eardrum) • The cavity of the tubotympanic recess gives rise to the tympanic cavity and mastoid antrum
  82. 82. Derivatives of Second Pharyngeal Pouch • The second pharyngeal pouch is largely obliterated as the palatine tonsils develop • Part of the cavity of this pouch remains as the tonsillar sinus or fossa • The endoderm of the pouch proliferates and grows into the underlying mesenchyme
  83. 83. Continued: • The pouch endoderm forms the surface epithelium and the lining of the tonsillar crypts • At about 20 weeks the mesenchyme around the crypts differentiates into lymphoid tissue • These tissues soon organize into the lymphatic nodules of the palatine tonsil
  84. 84. Derivatives of Third Pharyngeal Pouch • The primordia of thymus and parathyroid glands lose their connections with the pharynx and migrate into the neck • Later the parathyroid glands separate from the thymus and lie on the dorsal surface of the thyroid gland
  85. 85. Derivatives of Fourth Pharyngeal Pouch • The fourth pharyngeal pouch also expands into dorsal bulbar and elongate ventral parts • Its connection with the pharynx is reduced to a narrow duct that soon degenerates • By the sixth week, each dorsal part develops into a superior parathyroid gland • It lies on the dorsal surface of the thyroid gland
  86. 86. Continued: • The parathyroid glands derived from the third pouches descend with the thymus and are carried to a more inferior position than the parathyroid derived from the fourth pouches • This explains why the parathyroid glands derived from the third pair of pouches are located inferior to those from the fourth pouches
  87. 87. The Fifth Pharyngeal Pouch • When this develops, this rudimentary pouch becomes part of the fourth pharyngeal pouch and helps to form the ultimopharyngeal body
  88. 88. Pharyngeal Grooves • During the fourth and fifth weeks, head and neck region of the human embryo exhibit four pharyngeal grooves or clefts on each side • These grooves separate the pharyngeal arches externally • Only first pair persists as the external acoustic meatus • The other grooves normally obliterated with the cervical sinus as the neck develops
  89. 89. Pharyngeal Membranes • Pharyngeal membranes appear in the floor of the pharyngeal grooves • These membranes form where the epithelia of the grooves and pouches approach each other • The endoderm of the pouches and ectoderm of the grooves are soon separated by mesenchyme • Only first pharyngeal membrane becomes the tympanic membrane, others obliterate
  90. 90. The First Pharyngeal Arch Arch derivatives Muscle Mastication muscles (temporal, masseter, medial and lateral pterygoids), mylohyoid, anterior belly of the digastric, tensor velli palatini, tensor tympanI Bone and cartilage Mandible, maxilla, premaxilla, zygomatic bone, squamous part of the temporal bone, pinna of the ear (anterior), Meckel's cartilage (malleus, incus) Other connective tissue Anterior ligament of the malleus, sphenomandibular ligament Pouch derivatives Middle ear cavity, auditory (Eustachian) tube, tympanic membrane Cleft derivatives External auditory meatus Nerve supply V (trigeminal nerve)
  91. 91. The Second Pharyngeal Arch Arch derivatives Muscle Facial expresion muscles, stapedius, stylohyoid, posterior belly of the digastric Bone and cartilage Reichert's cartilage (stapes, styloid process), hyoid bone (leser horn and upper body), pinna of the ear (posterior) Other connective tissue Stylohyoid ligament Pouch derivatives Palatine tonsils Cleft derivatives None Nerve supply VII (facial nerve)
  92. 92. The Third Pharyngeal Arch Arch derivatives Muscle Stylopharyngeus Bone and cartilage Hyoid bone (greater horn and lower part of the body) Other connective tissue None Pouch derivatives Inferior parathyroid, thymus Cleft derivatives None Nerve supply IX (glossopharyngeal nerve)
  93. 93. IV - VI Pharyngeal Arch Arch derivatives Muscle Cricothyroid, levator velum palatini, constrictors of pharynx, intrinsic muscles of the larynx Bone and cartilage Laryngeal cartilages (cricoid, thyroid, arytenoid, corniculate, cuneiforme) Other connective tissue None Pouch derivatives Superior parathyroid, ultimobranchial bodies of the thyroid Cleft derivatives None Nerve supply X (superior and recurrent laryngeal branch of the vagus nerve)
  94. 94. Branchial fistula, sinus, cyst An abnormal canal that opens internally into tonsillar sinus and externally in the side of the neck is branchial fistula. Due to persistence of parts of second pharyngeal groove and pouch. The birth defect may appear as open spaces called cleft sinuses, which may develop on one or both sides of the neck. A branchial cleft cyst may form from fluid drained from a sinus. The cyst or sinus can become infected. Reference: 1.Clin Otolaryngol Allied Sci. 1978 Feb;3(1):77-92. Branchial cysts, sinuses and fistulae. Maran AG, Buchanan DR. 2.”The developing Human “, 8th ed, Keith Moore
  95. 95. Branchial Sinus Branchial Fistula
  96. 96. • Lie free in the neck just inferior to the angle of mandible. • Develop anywhere along anterior border of sternocleidomastoid • Become apparent in late childhood or early adulthood Branchial cyst
  97. 97. Piriform Sinus Fistula • It is thought to result from the persistence of remnants of the ultimopharyngeal body. • The fistula traces the path of this embryonic body to the thyroid gland.
  98. 98. Branchial Vestiges • Remnants of pharyngeal arch cartilages under the skin in the side of the neck. • Found anteriorly to the inferior third of sternocleidomastoid muscle
  99. 99. First Arch Syndrome • Abnormal development of the components of first pharyngeal arch results in various congenital anomalies of the eyes, ears, mandible and palate that together constitute the first arch syndrome. • Believed to result from the insufficient migration of neural crest cells into the first arch during the fourth week.
  100. 100. First Arch Syndrome Two main manifestations: • Treacher collins syndrome • Pierre robin Syndrome
  101. 101. Treacher Collins Syndrome Also called as mandibulofacial dysostosis. autosomal dominant congenital disorders. Features: • Malar hypoplasia • Down-slanting palpebral fissures • Micrognathia • conductive hearing loss • malformed or absent ears.
  102. 102. Pierre Robin Syndrome Autosomal recessive disorder Features: • Hypoplasia of mandible • Cleft palate • Defects of eye and ear are present
  103. 103. Robin morphogenetic complex Initiating defect is a small mandible Results posterior displacement of tongue Obstruction to full closure palatal processes Resulting in bilateral cleft palate
  104. 104. DiGeorge syndrome Occurs because the third and fourth pharyngeal pouches fail to differentiate Into thymus and parathyroid glands As a result of breakdown in signalling between pharyngeal endoderm and adjacent neural crest cells
  105. 105. Features: • Shortened philtrum of lip(fish mouth deformity) • Low set ears • Nasal clefts • Thyroid hypolplasia • cardiac abnormalities
  106. 106. NEURAL CREST CELLS Neural crest cells originating in the neuroectoderm form the facial skeleton and most of skull. Often a target of teratogens. Crest cells are easily killed by compounds such as retinoic acid and alcohol This is because these cells are deficient in superoxide dismutase and catalase enzyme which are basically free radical scavengers.
  107. 107. Example of craniofacial defects involving neural crest cells include : • Treacher collins syndrome • Robins sequence • Goldenhar syndrome
  108. 108. Goldenhar syndrome • Also known as oculo-auriculovertebral (OAV) syndrome • Anomalous development of the first branchial arch and second branchial arch. • Rare congenital defect. Features: • Incomplete development of the ear, nose, soft palate, lip, and mandible on usually one side of the body.
  109. 109. CONCLUSION Growth and development of the craniofacial structures is a complex interplay of a variety of factors. A thorough understanding of the intricate interactions of related structures is necessary to understand and differentiate between the normal and the abnormal, to aid in the diagnosis, management and treatment planning of different anomalies.
  110. 110. REFERENCES Langman’s medical embryology. 9th Ed., 2004, Lippincott, Williams & Wilkins. •Human Embryology – I B Singh, 6th edition. Enlow DH. Handbook of facial growth. 2nd Ed.,1982 Graber TM. Principles and practice of orthodontics. 3rd Ed.,1966. Craniofacial Development : Geoffrey H. Sperber Proffit WR. Contemporary orthodontics. 3rd Ed., 2000, Mosby, Inc.

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