Development of the face - Copy - Copy - Copy.pptx

Human face starts to develop at 4th week of embryonic development
External face formation is completed by the 8th week
Anatomical structures are the most diverse in the face compared to other regions of the body
Development is a continuous process which does not stop at birth
EMBRYOLOGY
Science of the origin & development of the organism from fertilization of the ovum to the end of the eighth week.

GROWTH
GRABER: a positive change in size ,often over a period of time.
KROGMAN: increase in size, change in proportion and progressive complexity.
TODD: An increase in size.
MOSS: Change in any morphological parameter which is measurable

1.           DEVELOPMENT OF THE FACE DR. NOORI MOINUDEEN FIRST YEAR MDS DEPARTMENT OF ORAL PATHOLOGY GDC CALICUT

2. CONTENTS INTRODUCTION EMBRYONIC PERIOD AND GERM LAYERS PHARYNGEAL ARCHES DEVELOPMENT OF HEAD, SKULL AND FACIAL  STRUCTURES DEVELOPMENT OF FACE DEVELOPMENTAL ANOMALIES CONCLUSION

3. INTRODUCTION Human face starts to develop at 4th week of embryonic development External face formation is completed by the 8th week Anatomical structures are the most diverse in the face compared to other regions of the body Development is a continuous process which does not stop at birth

4. DEFINITION EMBRYOLOGY Science of the origin & development of the organism from fertilization of the ovum to the end of the eighth week. GROWTH GRABER: a positive change in size ,often over a period of time. KROGMAN: increase in size, change in proportion and progressive complexity. TODD: An increase in size. MOSS: Change in any morphological parameter which is measurable

5. DEVELOPMENT Moyers: development refers to all the naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death. Thus it encompasses the normal sequential events between fertilization and death. Todd(1931): Development is the progress towards maturity. DIFFERENTIATION It is the change from a generalized cell or tissue to one that is more specialized. It is change in quality or kind.

6. SEQUENCE OF PRENATAL DEVELOPMENT

7. EARLY EMBRYONIC DEVELOPMENT PERIOD OF OVUM - From fertilization to 14 th day. PERIOD OF EMBRYO- From 14 th day to 56 th day. PERIOD OF FETUS- From 56 th day till birth

8. PRE-IMPLANTATION PERIOD The period of one week from fertilization to implantation of the fertilized egg is called the pre-implantation period.

9. EMBRYONIC PERIOD The period of embryo is divided into 3 stages PRESOMITE stage – an embryo in any stage of development before the appearance of the first pair of somites (primitive segments/metameres), which in humans usually occurs around 19 to 21 days after fertilization of the ovum. SOMITE stage - an embryo in any stage of development between the formation of the first and the last pairs of somites, which in humans occurs in the third and fourth weeks after fertilization of the ovum. POSTSOMITE stage - t he developing embryo then gets attached to the uterine endometrium, this is called Implantation. After Implantation the endometrium is called Decidua. The placenta is formed partly by embryonic structures and partly from the decidua.

10. FORMATION OF GERM LAYERS Fertilization of ovum takes place in the ampulla of the uterine tube. When there are 16 cells the ovum is called a morula. The cells of the inner cell mass rearrange to form the embryonic disc having two germ cells namely ECTODERM & ENDODERM and the third layer is formed between these 2 layers. It is known as MESODERM.

11. Bilaminar disc formation

12. BILAMINAR EMBRYO STAGE

13. PROCHORDAL PLATE Prochordal plate

14. PRIMITIVE STREAK FORMATION On day 15, a groove called the primitive streak , appears on the surface of the midline of the dorsal aspect of the ectoderm of the embryonic disc. By day 16, a primitive knot of cells, the Henson’s node , appears at the cephalic end( rostral ) of the primitive streak. This knot gives rise to the cells that form the notochordal process.

15. NOTOCHORD FORMATION Cells of the ectoderm divide at the primitive node; migrate in between ectoderm and endoderm to form a solid column that pushes forward in the midline as far as the prochordal plate. Through canalization of these cord of cells notochord is formed to support the embryo. Notochordal cells induce overlying ectoderm to form neural plate that forms neural groove with neural crest cells at its edges

16. Gastrulation –conversion of the bilaminar embryo into a trilaminar embryo. The left column illustrates the plane of section for the middle and right columns. The middle column provides a three-dimensional view, and the right column provides a two-dimensional representation. A, The floor of the amniotic cavity, formed by the ectodermal layer of the bilaminar embryo. Ectodermal cells converge toward the midline to form the primitive streak, a narrow groove terminating in a circular depression called the primitive node. Ectodermal cells then migrate through the streak and between the ectodermal and endodermal layers in lateral and cephalic directions (arrows). A notochord process extends forward from the primitive node. B, A transverse section through x-x1, showing the notochord flanked by mesoderm. C, A section through y-y1. D, Notochord pushing rostrally as seen in longitudinal section.

17. MESODERM FORMATION Cells from the primitive streak and the notochordal process migrate laterally between the ectodermal and endodermal layers of the embryonic shield. These cells form the third germ cell layer called the mesodermal layer .

18. NEURULATION

19. FORMATION OF NEURAL TUBE

20. NEURAL CREST CELLS Unique population of cells developing from the ectoderm along the lateral margins of the neural plate. Undergo extensive migrations, beginning at about the time of tube closure. Neural crest cells in the trunk region:- form neural, endocrine and pigment cells Neural crest cells in the head and neck:- form skeletal and connective tissue of face Except enamel, all other skeletal and connective tissue of upper facial region - formed by ECTOMESENCHYME (neural crest cells move around the sides of the head beneath the surface ectoderm, as a sheet of cells.)

21. NEURAL CREST CELLS Clinical significance : failure of proper migration of neural crest cells will result in Treacher collin syndrome.

22. FOLDING OF EMBRYO Onset at 24 days

23. DEVELOPMENT OF SKULL The Skull can be divided into 3 components; 1.The cranial vault 2. The cranial base 3. The face Membranous bone formed directly in mesenchyme with no cartilaginous precursor, forms the cranial vault and face. The cranial base is formed by endochondral ossification. Membrane formed bones may develop secondary cartilages to provide rapid growth.

24. Anterior portion of the neural tube expands to form the forebrain, midbrain and hindbrain. Hindbrain appears as 8 partially segmented portion called as rhombomeres. DEVELOPMENT OF THE HEAD

25. Lateral to the neural tube is paraxial mesoderm which partially segments rostrally to form seven somatomeres and fully segments caudally to form somites , first being occipital somites . Neural crest cells from m idbrain along with the 1st rhombomere (ectomesenchyme associated with the face)and 2 nd rhombomere (first branchial arch for jaw formation) supply additional connective tissue for craniofacial development. The remaining rhombomeres will give rise to the pharyngeal arches.

26. DERIVATIVES OF GERM LAYERS

27. DEVELOPMENT OF PHARYNGEAL ARCHES Pharyngeal arches are rod like thickenings of mesoderm present in the wall of the foregut. At first there are 6 arches. The 5 th arch disappears and then only 5 arches remain. In the interval between any two arches the endoderm (lining of the pharynx) is pushed outwards to form a series of pouches. These are called Pharyngeal pouches.

28. COMPONENTS OF PHARYNGEAL ARCHES Cartilage component : Adapts to form Bony, Cartilaginous or Ligamentous structures Muscle component : Give rise to special visceral muscles composed of striated muscle fibers. Vascular component : Provides necessary blood supply Nerve component : Enters mesoderm of the brachial arches and initiates neural development of mesoderm

29. DEVELOPMENT OF FACIAL SKELETON Face may be conveniently, somewhat arbitrarly divided into upper, middle and lower thirds. The three parts generally correspond to the embryonic structures namely frontonasal process, maxillary and mandibular process.

30. Upper third of the face is predominantly of neurocranial composition with the frontal bone of the calvaria primarily responsible for the forehead. Middle third of the face is skeletally the most complex, being composed in part of the cranial base and incorporating the nasal extensions of the upper third and part of the maxillary apparatus. Grows more slowly over a prolonged period, not ceasing the growth until the late adolescence. The lower third of the face completes the masticatory apparatus being composed of the skeleton of mandible and its dentition.

31. DEVELOPMENT OF FACE Face develops from 3 prominences that surround the stomatodeum , a depression bounded cranially by a bulging produced by the brain and caudally by the pericardial cavity. 1.Frontonasal process 2.Right and Left mandibular arch The mandibular arch divides into a maxillary process and a mandibular process. The right and the left mandibular arches meet in the midline and fuse. They form the upper and lower lips.

32. Frontonasal region Includes olfactory placode, primary palate and nose 1 st structures formed are thickening of ectoderm to form placodes that form nasal prominences The medial nasal process of both sides together with the frontonasal process give rise to middle portion of the nose, middle portion of upper lip, anterior portion of maxilla and the primary palate. Maxillary process grows medially and approaches the lateral and medial nasal process but remains separated from them by distinct groove- naso -optic and bucconasal groove. Maxillary process grow medially and pushes the medial nasal process towards midline and merges with the anatomic counterpart.

33. DEVELOPMENT OF UPPER & LOWER LIPS Upper lip – by maxillary process of each side and medial nasal process. Lower lip – by merging of the ectomesenchyme of the mandibular process.

34. DEVELOPMENT OF CHEEKS After formation of upper and lower lips, stomatodeum appears very broad. On the lateral side it is bounded above by the maxillary process and below by the mandibular process. The maxillary and mandibular process fuse to form the cheeks.

35. DEVELOPMENT OF MOUTH The mouth is derived partly from the stomatodeum (ectodermal) and partly from the foregut(endodermal). After the disappearance of the buccopharyngeal membrane the stomatodeum communicates with the foregut. Epithelium lining the lips, cheek, palate, teeth and gums are ectodermal in origin. Epithelium of the tongue is endodermal. In the region of the floor of the mouth, mandibular process forms the lower lip, lower parts of the cheek, lower jaw and tongue.

36. DEVELOPMENT OF TEETH Primary epithelial band is a band of epithelium that has invaded underlying ectomesenchyme along each of the horse shoe shaped future dental arches. At the 7 th week the primary epithelial band divides into Dental lamina and Vestibular lamina. The Dental lamina shows a series of local thickenings called the Enamel organ. The D ental lamina is established in the sixth week of intrauterine life. The Dental lamina serves as a primordium of the ectodermal position of the deciduous teeth Permanent molars arise directly from a distal extension of the dental lamina. Dental lamina extends over a period of atleast 5 years.

37. DEVELOPMENT OF SALIVARY GLAND The salivary glands develop as outgrowths of the buccal epithelium. The outgrowths are at first solid and are later canalized. They branch repeatedly to form the duct system. The terminal part of the duct system develop into secretory acini. The outgrowths of the parotid gland arise in relation to the line along which the maxillary and mandibular processes fuse to form the cheek. It is ectodermal. The outgrowths for the submandibular and sublingual glands arise in relation to the linguogingival sulcus. They are endodermal in origin.

38. DEVELOPMENT OF PALATE For each maxillary process a plate like shelf grows medially called palatal process. The palate is formed from 3 components -the two palatal processes -the primitive palate formed from the frontonasal process. The mesoderm in the palate undergoes intramembranous ossification to form the hard palate.

39. Ossification does not extend into the posterior portion called the soft palate. The part of the palate derived from the frontonasal process forms the premaxilla which carries the incisor teeth. After the development of the secondary palate, distinction between the oral and nasal cavity is possible. Development begins at 7 -8 weeks and completes in the 3 rd month of gestation. 3 outgrowths appear – one nasal septum and two palatine shelves. T hey converge and fuse in the midline. Displacement of the tongue from in between the palatine shelves by the growth pattern of the head is a contributing factor for the closure of the palate.

40. Formation of the secondary palate. Coronal sections through human embryos at approximately (A) 7 weeks, (B) 8 weeks, and (C) 9 weeks of development. The initial disposition of palatine shelves on each side of the tongue is shown in A, their elevation coincident with depression of the tongue in B, and their final fusion with each other and with the nasal septum in C.

41. SECONDARY PALATE FORMATION

42. DEVELOPMENT OF NOSE The nose has a contributions from: Frontal prominence - The bridge Medial nasal prominence - Median ridge and tip Lateral nasal prominence - The alae The cartilage of nasal capsule - the septum and nasal conchae. As the nose becomes prominent, the external nares open up downwards instead of forwards.

43. DEVELOPMENT OF PARANASAL SINUSES Paranasal sinuses develop during late fetal life. They form as outgrowths or diverticula of the walls of the nasal cavities and become air filled extensions of the nasal cavities in the adjacent bone. Frontal – 3 to 4 months of I.U Ethmoidal – 4 months of I.U Maxillary – Develops at 10 weeks of I.U Sphenoidal – 4 months of I.U

44. DEVELOPMENT OF EYE Eyes develop from three sources: Neuroectoderm of the forebrain - retina , optic nerve. Surface ectoderm of the head- lens Mesoderm between these layers - eye muscle and vascular tissues 1st indication of eye formation is optic vesicles which is formed in the 4th week.

45. DEVELOPMENT OF EAR Ear consists of 3 anatomical parts: - Ex ternal ear - Middle ear - In ternal ear External ear : External acoustic meatus:- Develops by deepening of the dorsal end of the 1st pharyngeal groove. Pinna or Auricle: Six mesenchymal hillocks – Auricular hillocks develop from the 1st and 2nd pharyngeal arch.

46. Middle ear: Develops from the tubotympanic recess that is derived from the 1st pharyngeal pouch. Tympanic cavity- Distal portion of the tubotympanic recess expands. Tympanic membrane: Ectodermal lining from first pharyngeal groove Mesodermal lining from 1st and 2nd arch Endodermal lining from tubotympanic recess

47. Ear ossicles : •1st bone to attain ultimate size. •Malleus and Incus develop from the 1st arch. •Stapes develop from 2nd arch. •Ossification begins in the 16th week and continues up to the 25th week INTERNAL EAR: • develops from the OTIC PLACODE

48. DEVELOPMENT OF TONGUE Tongue develops in relation to pharyngeal arch in the floor of the developing mouth. The medial most part of mandibular arch proliferate to form Lingual swellings. They are partially separated from each other by another swelling in midline called Tuberculum Impar . Immediately behind Tuberculum Impar the epithelium proliferates to form a downgrowth(thyroglossal duct) from which thyroid gland develops. This site is marked by Foramen Caecum . Hypobranchial eminence- midline swelling in relation to medial ends of 2nd, 3rd, & 4th arch. It has a cranial part called Copula (2nd, 3rd ), & caudal part ( 4th) forming epiglottis.

49. Anterior two-thirds of tongue forms by fusion of 2 L ingual swellings & Tuberculum impar. It is derived from Mandibular arch, so supplied by lingual nerve, branch of Mandibular nerve which is post- trematic nerve of the 1st arch & chorda- tympani which is pre- trematic nerve of the arch. Posterior one-third is formed from cranial part of hypobranchial eminence(copula). The 2nd arch mesoderm buries below the surface, 3rd arch mesoderm grows over it to fuse with mesoderm of 1st arch. Thus it is formed by 3rd arch mesoderm. Supplied by glossopharyngeal nerve, of 3rd arch.

50. The posterior most part is formed from 4th arch, so it is supplied by superior laryngeal nerve of 4th arch. Musculature is derived from occipital myotomes, supplied by hypoglossal nerve .

51. DEVELOPMENT OF MAXILLA Maxilla develops from ossification in mesenchyme of maxillary process of 1 st arch No arch cartilage/primary cartilage Centre of ossification- close to cartilage of nasal capsule & in angle of division of infraorbital nerve From this centre bone formation spreads: Posteriorly-below orbit toward developing maxilla Anteriorly-toward future incisor region Superiorly-to form frontal process Medially-to form palate Bony trough for infraorbital canal is formed

52. DEVELOPMENT OF MANDIBLE On lateral aspect of Meckel’s cartilage (1st arch cartilage) during 6th week of embryonic development, a condensation of mesenchyme occurs in the angle formed by division of Inferior Alveolar Nerve and its incisive and mental branches At 7th week ,intra membranous ossification begins in this condensation forming the 1st bone of the mandible. From this centre of ossification, bone formation spreads rapidly, anteriorly to the midline and backwards towards the point where the mandibular nerve divides into lingual and IAN branches.

53. Ramus of mandible develops by a rapid spread of ossification backwards into mesenchyme of 1st arch, diverging away from Meckel’s cartilage. The point of divergence, is marked by lingula in adult mandible, where IAN enters body of mandible.

54. By 10th week, rudimentary mandible is formed entirely by membranous ossification with no direct involvement of Meckel’s cartilage. Further growth is influenced by secondary (growth) cartilage and development of muscular attachments. The cartilages are condylar, coronoid and symphyseal cartilages .

55. MECKEL’S CARTILAGE :- Dorsal end ossifies to form malleus & incus Its parts then transform into sphenomandibular ligament & ant. Malleolar ligament Ventral end forms accessory endochondral ossicles Then between 10th -14th weeks, secondary accessory cartilages appear to form the head of condyle, part of coronoid process and mental protruberance . By 24th week it disappears

56. OVERVIEW

57. DEVELOPMENTAL ANOMALIES OF THE FACE

58. ANOMALIES OF LIPS AND PALATE Congenital lip pits Commissural lip pits and fistulas Van der woude syndrome Cleft lip and palate

59. Congenital lip pits A  congenital lip pit  or  lip sinus  is a congenital disorder characterized by the presence of pits and possibly associated fistulas in the lips. They are often hereditary and may occur alone or in association with cleft lip and palate, termed  Van der Woude syndrome . Pits may result from notching of the lip at an early stage of development ,with fixation of tissue at the base of the notch or from failure of complete union of the embryonic lateral sulci of the lip, which persist and ultimately develop into the typical pits.

60. Commissural lip pits and fistulas

61. Etiology Abnormal fusion of the palate and lips ,at days 30 - 50 post conception. Van der woude syndrome can be caused by deletions in the chromosome band 1q32 and linkage analysis has confirmed this chromosomal locus as the disease gene site. VAN DER WOUDE SYNDROME Also called Cleft Lip syndrome or Lip Pit syndrome

62. Characterized by : Unilateral or bilateral lip pits. Absent teeth Isolated cleft lip and palate. Associated with accessory salivary glands that empty into pits. Patients may have maxillary hypodontia. Missing maxillary pre molars

63. Cleft lip and palate Cleft palate - A congenital fissure in the roof of the mouth, resulting from incomplete fusion of the palate during embryonic development . Cleft lip - A congenital deformity characterized by a vertical cleft or pair of clefts in the upper lip, with or without involvement of the palate. Defective fusion of the medial nasal process with the maxillary process leads to cleft lip Cleft lip is common among males while cleft palate is more common among females. Unilateral clefts - 80% of the incidence Bilateral clefts - remaining 20%.

64. Classification of Cleft Lip and Palate Most accepted: Veau’s Classification GROUP I:- cleft of the soft palate only. GROUP II:-Cleft of the hard and soft palate to the incisive foramen. GROUP III:-Complete unilateral cleft of the soft and hard palate, and the lip and alveolar ridge on one side. GROUP IV:-Complete bilateral cleft of the soft and hard palate ,and the lip and alveolar ridge on both sides.

65. DENTAL PROBLEMS Congenitally missing teeth (most commonly the upper laterals) Presence of natal or neonatal teeth Presence of supernumerary teeth Ectopically erupting teeth Anomalies of tooth morphology Enamel hypoplasia Microdontia Fused teeth Macrodontia Mobile and early shedding of teeth due to poor periodontal support Posterior and anterior cross bite Protruding premaxilla Deep bite, spacing, crowding

66. AESTHETIC PROBLEMS The clefts involving the lip can result in facial disfigurement varying from mild to severe. The oro -facial structures may be malformed and congenitally missing. Deformities of nose can also occur. Thus esthetics is greatly affected. HEARING AND SPEECH Cleft lip and palate are sometimes associated with disorders of the middle ear which may affect hearing. The presence of hearing problems can cause difficulties in language uptake and speech.

67. ANOMALIES OF TEETH

68. ANOMALIES OF SALIVARY GLAND Aberrancy / ectopic salivary gland : S tafne cyst Aplasia :Salivary gland aplasia (also termed  salivary gland agenesis ) is the congenital absence of salivary glands. Usually the term relates to the absence of some or all of the major salivary glands. Hypoplasia : relative underdevelopment of the Salivary glands. Salivary gland hypoplasia tends to produce xerostomia(dry mouth), with all the associated problems this brings. Hyperplasia Atresia : is congenital blockage or absence of the orifice of a major salivary gland duct or part of the duct itself.

69. Stafne cyst Stafne cysts , also known as a  static bone cavity of the mandible  or  lingual salivary gland inclusion defect , are cortical defects near the angle of the mandible below the mandibular canal.  Strictly speaking, it is not a cyst since it does not contain any fluid. It is usually an incidental finding and represents a depression in the medial aspect of the mandible filled by part of the submandibular gland or adjacent fat. 

70. ANOMALIES OF NOSE AND NASAL CAVITY Bifid nose: a rare birth defect of the nose. This malformation causes the nose to be divided into two separate parts. Some people with a  bifid nose  have a genetic condition called BNAR syndrome or "bifid nose, renal agenesis and anorectal malformations syndrome" that is caused by a change in the FREM1 gene. occurs when the right and left sides of the nose namely the lateral and medial nasal process fail to connect properly.

71. Proboscis: elongated nose or snout In teratology,  proboscis  is a blind-ended, tube-like structure, commonly located in the midface. Proboscis formation are classified in four general types: holoprosencephalic proboscis, lateral nasal proboscis, supernumerary proboscis, and disruptive proboscis.

72. ANOMALIES OF THE EYE Cyclopia : (also  cyclocephaly  or  synophthalmia ) is a rare form of holoprosencephaly and is a congenital disorder characterized by the failure of the embryonic prosencephalon to properly divide the orbits of the eye into two cavities. Its incidence is 1 in 16,000 in born animals and 1 in 200 in miscarried fetuses. Anophthalmia : absence of eye Congenital ptosis: Cryptophthalmos : fusionof eyelids

73. Colobomas of eyelid An eyelid coloboma is a full-thickness defect of the eyelid. Although an eyelid coloboma can occur in many locations, the most common position is at the junction of the medial and middle third of the upper lid. No lid appendages or accessory structures are usually seen within the coloboma. An eyelid coloboma may occur either congenitally or as a result of trauma ( eg , accidental, surgical). An eyelid coloboma is an almost constant feature of  Treacher Collins syndrome, which is autosomal dominant with variable penetrance and expressivity.

74. ANOMALIES OF THE EAR Preauricular pits and appendages Skin tags and shallow depression anterior to the ear Pits may indicate abnormal development of the auricular hillocks and appendages may be caused by accessory hillocks

75. Congenital deafness Absence of the tympanic cavity and external meatus Abnormal development of membranes and bony labyrinth Malformation of auditory ossicles and ear drum Caused by: Rubella virus Poliomyelitis Erythroblastosis fetalis Diabetes Hypothyroidism T oxoplasmosis

76. ANOMALIES OF THE TONGUE Ankyloglossia Macroglossia Microglossia Aglossia Bifid tongue Fissured tongue /scrotal tongue/lingua plicata.

77. ANOMALIES OF THE JAWS AGNATHIA MICROGNATHIA MACROGNATHIA C/F: Mandibular protrusion (when mandible is affected) "Gummy smile" (when maxilla is affected) Ramus of mandible forms a less steep angle with body of mandible Mandibular prognathism caused by excessive condylar growth Chin appears prominent

78. FACIAL HEMIHYPERTROPHY Asymptomatic growth of one or more body parts Involvement of one side of the face FACIAL HEMIATROPHY Slowly progressive atrophy of soft tissue of essentially half the face characterized by progressive wasting of sub cutaneous fat accompanied by atrophy of skin , cartilage , bone and muscle.

79. CHROMOSOME ABNORMALITIES TURNER’S SYNDROME:- Turner’s syndrome is caused by the absence of two complete copies of the X chromosome in some or all the cells. 44+XO Multiple eye findings including cataract, blue sclera. Color Blindness Depressed Corners of mouth High arched palate Dental malocclusion Micrognathia

80. TRISOMY 21/DOWNS SYNDROME/MONGOLISM C/F:- Hypoplastic maxilla and nasal bones Flattening of nasal bridge, orbital ridges, and maxilla Short hard palate Cleft lip/palate about 3 times frequency in normal population Protruding fissured tongue with hypertrophy of papillae Dentition delayed, increased periodontal disease, and reduced dental caries

81. CROUZONS SYNDROME/CRANIOFACIAL DYSOSTOSIS Premature closure, especially of coronal suture, occasionally lambdoidal. Variable cranial form depending on order and rate of progression of suture closure Optic nerve damage High arched palate V-shaped maxillary dental arch. Crowding of the upper teeth. Class III Malocclusion Bilateral Atresia of Auditory meatus noted occasionally Mental retardation occasionally seen anomalies of the hands and feet may or may not occur.

82. NEURAL CREST CELLS & CRANIOFACIAL DEFECTS Craniofacial defect involving with neural crestal cells include: Treacher C ollin syndrome Pierre Robin syndrome De G eorge anomaly Occulo A uriculo V ertbral S pectrum(Goldenhar syndrome)

83. TREACHER COLLIN SYNDROME U nder development of the zygomatic bones, mandibular hypoplasia, down slanting palpebral fissures, malformed external ears Autosomal dominant trait with 60% cases Macrostomia Hypoplastic mandible with concave undersurface Hypoplastic zygomatic arches C left palate Dental malocclusion common Pinna frequently deformed crumpled forward, or misplaced Absence of external auditory canal

84. PIERRE ROBIN SYNDROME Altered first arch structure Occur independently or in association with other malformations Development of mandible most severely affected M icrognathia, cleft palate and glossoptosis (posteriorly placed tongue) M ay be due to genetic or environmental factors May also occur as a deformation The primary defect includes poor growth of the mandible and as a result a posteriorly placed tongue that fails to drop from between the palatal shelves preventing their fusion

85. MARFAN’S SYNDROME Autosomal dominant trait C/F_ P rominent supraorbital ridges Long narrow face High arched palate Mandibular prognathism Myopia Blue sclerae Chest deformities Hyperextensibility of joints Hernias Muscular underdevelopment

86. DE GEORGE ANOMALY Characterized by : H ave immunological deficiencies, hypocalcaemia and poor prognosis Origin of the defect is caused by abnormal development of neural crest cells that contribute to formation of all affected structures In addition to genetic causes, alcohol and maternal diabetes can produce such defect D efects in the palate M ild differences in facial features,

87. OCULOAURICULOVERTEBRAL SPECTRUM/HEMIFACIAL MICROSTOMIA C raniofacial abnormalities involving the maxillary, temporal and zygomatic bones which are small and flat Ear ( anotia -no ear), eye(tumors and dermoid in eye balls) Asymmetry -65% cases Other malformations- Tetralogy of F allot (congenital heart disease), malformations of kidney and intestine

88. HAZARDS IN PRENATAL DEVELOPMENT BY TERATOGENS Teratogens are any agents from the environment that can cause harm to the developing fetus. Many harmful agents cause damage only if exposure occurs during a sensitive period of prenatal development. Critical factors that influence the degree of harm a teratogen will cause: – The amount and length of exposure – Individual differences in susceptibility

89. Damage from teratogens is not always evident at birth but may appear later in life. Impact of teratogens often depends on quality of postnatal environment. About 45% or more pregnancies end in miscarriage, that is, spontaneous abortion. Most miscarried fetuses have severe defects, such as missing chromosomes, that make further development impossible. Ninety percent of fetuses that survive the danger of miscarriage are born normal

90. RISK FACTORS SMOKING ALCOHOL DIETARY DEFICIENCIES DISEASES by cytomegalovirus, herpes virus, parvovirus B19, rubella virus (German measles), syphilis, toxoplasmosis, Venezuelan equine encephalitis virus DRUGS Aspirin : pregnant women - blood disorders in offspring. T halidomide : deformations of the eyes, nose, ears cleft plate, facial palsy and fusing of fingers and toe , dislocations of the hip joint and malformations of the heart and digestive and urinary tract

91. Illegal drugs Marijuana: prenatal exposure to marijuana leads to infants reduced weight and size, short term changes in behaviour e.g. increased startle and a high pitched cry. Cocaine: effect of maternal cocaine use - children tend to be impulsive, highly distractable and difficult to control and to have problems in language development as they grow old.

92. CEPHALIC DISORDERS Cephalic disorders are congenital conditions that stem from damage to or abnormal development of the budding nervous system. ANENCEPHALY is a neural tube defect that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th days of pregnancy, resulting in the absence of a major portion of the brain, skull and scalp. HYDRANENCEPHALY is a rare condition in which the cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid.

93. INIENCEPHALY is a rare neural tube defect that combines extreme retroflexion (backward bending) of the head with severe defects of the spine. MEGALENCEPHALY, also called macrencephaly, is a condition in which there is an abnormally large, heavy, and usually malfunctioning brain. MICROCEPHALY is a neurological disorder in which the circumference of the head is smaller than average for the age and gender of the infant or child

94. CONCLUSION A thorough knowledge of the various complex processes involved during the development of the face is essential to understand the intricate design of the face as well as any abnormalities or developmental defects involving any of the stages of development. P roper diagnosis of any structural or functional imbalance is essential for successful treatment planning.

95. REFERENCES Human Embryology – I. B. Singh -7 th edition A.R. Tencate “Oral histology”. 9th edition. Shafer “A textbook of Oral pathology”. 7 th edition. B.D. Chaurasia “Human anatomy: Head and neck”. 3 rd edition. Orban’s oral histology &embryology :13 th edition

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