Prenatal growth /certified fixed orthodontic courses by Indian dental academy

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  • 1. 1
  • 2. Prenatal growth & development INDIAN DENTAL ACADEMY Leader in continuing dental education 2
  • 3. Contents Embryogenesis The preimplantation period The embryonic period The fetal period Pharyngeal arches’ pouches and grooves Craniofacial development 3
  • 4. Contents Prenatal development of Mandible Maxilla Palate Tongue Odontogenesis Teratogenic effects on embryonic development Conclusion References 4
  • 5. Male & female gametes Cells present in sex organs or gonads– carry out reproductive function Gonads produce highly specialized gametes Male gonad– testis-- spermatozoa Female gonad– ovary-- ova Spermatogenesis & oogenesis --- Gametogenesis One spermatozoa fuses with one ovum-fertilization 5
  • 6. Spermatogenesis 44+x+y Spermatogonium type A 44+x+y Type B 44 + x +y Primary spermatocyte 1st meiotic div 22 + x 22+x Secondary 22 + y spermatocyte 22+x 22+y 2nd meiotic div 22+y Spermatids 6
  • 7. Oogenesis 44 + X + X Oogonium Enlarges to form 44 + X + X Primary oocyte I meiotic division Secondary oocyte 22 + X 22+x I polar body 2nd meiotic division ovum 22 + X 22 + X II polar body 7
  • 8. Fertilization 8
  • 9. Sex determination Spermatozoa– either x or y bearing Ova – x bearing ovum sperm ovum sperm 22 + X 22 + X 22 + X 22 + Y 44 + X + X 44 +X + Y Female Male 9
  • 10. Main results of fertilization Restoration of diploid number of chromosomes Determination of sex Initiation of cleavage 10
  • 11. 11
  • 12. Growth & development Post-natal Pre-natal Ovum 1-14th day Embryo 14th – 56th day Fetus 56th – 280th day 12
  • 13. Period of Ovum Preimplantation period ( 1st week ) Day 1– fertilization Day 2 –2 cell stage Day 3 – MORULA Day 4 – early blastocyst Day 5 -- late blastocyst 13
  • 14. Period of Ovum EVENTS IN PERIOD OF OVUM Fertilization Morulla formation 3rd day Blastocyst 4th & 5th day 14
  • 15. Period of Ovum Implantation ( 8th day ) Trophoblast sticks to uterine endometrium Blastocyst goes deeper into uterine mucosa until whole of it lies in thickness of endometrium---interstitial implantation 15
  • 16. Period of Ovum Bilaminar Germ Disc (2nd week) Formation of ectoderm & endoderm – ectoderm endoderm Amniotic fluid (8th day) Primary yolksac formation (9th day) 16
  • 17. Days 11, 12 & 13 Secondary yolksac formation 18
  • 18. Gastrulation: trilaminar germ disc Prochordal plate Embryonic disc forms prochordal plate & primitive streak (14th day) 19
  • 19. 20
  • 20. Formation of 3rd germ layer – Intraembryonic- mesoderm (16th day) 21
  • 21. Period of Embryo (3rd to 8th week) 22
  • 22. Period of Embryo Further development of Embryonic Disc 3rd week knot 23
  • 23. Period of Embryo Formation of Notochord By Day 19 24
  • 24. Development of mesoderm into 3 aggregations ( Transverse section) Day 17 Day 20 Day 19 Day 2125
  • 25. Period of Embryo Yolksac & Folding of embryo 4th week 27
  • 26. Cephalocaudal folding at various stages of development ( sagital midline section) End of I month 28
  • 27. 5 weeks old embryo 29
  • 28. Derivatives of germ layers & neural crest 30
  • 29. The Fetal Period (3rd month to Birth) 31
  • 30. Fetal Period Monthly changes (3rd month) Head constitutes half of crown rump length Face becomes more human looking Primary ossification centers are present in long bones & skull External genitalia develop 32
  • 31. Fetal Period 4th to 5th month Head size is 1/3rd of crown heel length Fetus lengthens rapidly Fetal movements can be felt by mother 33
  • 32. Fetal Period 6th to 7th month Fetus obtains well rounded contours due to deposition of subcutaneous fat 50% of full term weight added 34
  • 33. Fetal Period 9th month Skull has the largest circumference of all the parts of the body Normal weight: 3000- 3400 gms CRL – 36 cms CHL – 50 cms 35
  • 34. Craniofacial development 36
  • 35. Head formation Neural tube produced by formn & fusion of neural folds Anterior part of tube expands as forebrain, midbrain & hindbrain form but a small amount of mesenchyme remains– embryonic CT Lateral to neural tube is paraxial mesoderm segments to form somatomeres--somites 37
  • 36. Part of neural tube that forms hindbrain devps 8 bulges– rhombomeres Migration of neural crest – provides embryonic CT Neural crest cells arise from – midbrain & first 2 rhombomeres 38
  • 37. Migrating streams of neural crest cells express homeobox genes 39
  • 38. Pharyngeal arch During 4th week, lateral plate mesoderm of ventral foregut segments to form 5 bilateral mesenchyme swellings– pharyngeal arches 40
  • 39. Pharyngeal arches 41
  • 40. Each PHARYNGEAL ARCH consists of Central cartilage rod Muscular component Vascular component Nervous element 42
  • 41. Arch anatomy 43
  • 42. PHARYNGEAL ARCH NERVE Mandibular arch Trigeminal N. MUSCLES Cranial somatomere 4 CARTILAGE MECKEL’S: (41st - 45th day) Muscles of mastication malleus & incus Artery: Mylohyoid, Ant.belly of digastric, Maxilary Tensor tympani & sphenomandibu Artery lar lig.,ant.lig.of Part of ECA Tensor palatine malleus Hyoid arch Facial N. Cranial somatomere 6 ARTERY: Stapedial FACIALEXPRESSION, post.belly of digastric, stylohyoid, stapedius RIECHERT’S (45th - 48th day) Stapes,styloid P stylohyoid lig. lesser horn & upper body of hyoid 44
  • 43. PHARYNGEAL ARCH IIIrd arch NERVE Glossopharyngeal N. Artery: CCA IV th arch Vagus N. Superior laryngeal N. Artery: arch of aorta Right subclavian & brachicephalic MUSCLES SKELETON Stylopharyngeus Greater horn &lower body of Cranial hyoid somatomere 7 Cricothyroid Laryngeal Thyroid levator palatine, cartilages cartilage constrictors of pharynx Occiptal somites 2,4 VI th arch Recurrent laryngeal N. Intrinsic muscles of larynx Cricoid & arytenoid Artery: pulmonary & Ductus arteriosum Occiptal somites 1,2 45
  • 44. PHARYNGEAL POUCHES POUCH STRUCTURE FORMED First Second Auditory tube,middle ear cavity Palatine Tonsil Third Inferior parathyroids,Thymus Fourth Superior parathyroids, Fifth Parafollicular cells of thyroid 46
  • 45. PHARYNGEAL CLEFTS First cleft (dorsal) External acoustic meatus 2nd, 3rd & 4th clefts obliterate by caudal overgrowth of Hyoid arch 47
  • 46. Branchial arch anamolies Classification: Unilateral-- Hemifacial microsomia or Goldenhar’s syndrome Bilateral-- Mandibulofacial dysostosis 48
  • 47. Hemifacial microsomia or Goldenhar’s syndrome Features: i. assymetrical anamolies of pinna & middle ear ii. Deficiencies in malar, temporal & ramus iii. Facial paresis iv. Pseudomacrostomia 49
  • 48. Goldenhar’s syndrome Cause: Hematoma initiated in stapedial artery system Displacement & destruction of local mesenchyme Delay in the diff of 1st & 2nd arch structures Asymmetrical anomalies 50
  • 49. 51
  • 50. Treacher collin syndrome Pathogenesis: Neural crest cells syphoned away & redistributed in a haphazard fashion 52
  • 51. Anamolies of pharyngeal pouches Pharyngeal fistulae & cysts Etiology : o Defect in the development of the 2nd pharyngeal pouch 53
  • 52. Development of face ( 24th & 38th day) End of 4th week– facial prominences appear 54
  • 53. During 5th week nasal placodes invaginate to form nasal pits Edges of each pit raised above the surface Medial raised edge-MNP Lateral raised edge-LNP 55
  • 54. Formation of lip, nose & cheeks FNP 56
  • 55. Development of eye Ectodermal thickening – lens placode sinks below the surface & cut of from ectoderm Developing eyeball produces bulging directed laterally 57
  • 56. 58
  • 57. 59
  • 58. PROMINENCE STRUCTURES FORMED 1 Frontonasal Forehead, Bridge of nose, Medial & Lateral nasal prominences 2 Maxillary (P) Cheeks, lateral portion of upper lip & UPPER JAW 3 Medial nasal (P) Philtrum of upper lip, Crest & tip of nose 4 Lateral nasal Alae of nose (P) Mandibular(P) Lower lip & LOWER JAW 5 60
  • 59. Anomalies of face Defects of rhomboencephalic organizing center, which is responsible for induction of viscerofacial skeleton ---- account for dysmorphology of middle & lower 3rd of face. 61
  • 60. Anomalies of face Facial clefts Mandibular midline cleft: failure of mandibular process to merge Bilateral clefting of upperlip : failure of MNPs to merge with maxillary prominences 62
  • 61. Anomalies of face Unilateral cleft lip Median cleft lip Oblique facial cleft 63
  • 62. Anomalies of face Microstomia or macrostomia: Merging of maxillary & mandibular prominences beyond or short of the site for normal development 64
  • 63. Anomalies of face Fetal alcohol syndrome Deficiency in MNPs Features: mandible prognathic in reln to midface marked underdevelopment of premaxilla 65
  • 64. Anomalies of face The preventable tragedy: Fetal Alcohol Syndrome Seen in child whose mother consumes alcohol during pregnancy 66
  • 65. Anomalies of face Craniofacial developmental cysts Named acc. to site in which they develop: 1. Nasolabial cysts 2. Globulomaxillary cyst 3. Median mandibular cyst 67
  • 66. Development of tongue (4th week) Tongue arises in the ventral wall of primitive oropharynx from first 4 pharyngeal arches 68
  • 67. Development of tongue 69
  • 68. Development of tongue 70
  • 69. Development of tongue Taste buds arise by inductive interaction b/w epithelial cells & gustatory nerve cells Gustatory cells- 7th wk Taste buds– 13 -15 wks 71
  • 70. Development of tongue Muscles of tongue– floor of pharynx in occipetal somite region Embryological components retain initially established nerve supplies 72
  • 71. Anomolies of tongue Ankyloglossia Microglossia Abberant thyroid tissue Macroglossia Bifid / trifid tongue Aglossia 73
  • 72. DEVELOPMENT OF PALATE INTERMAXILLARY SEGMENT: Formed by merging of the 2 medial nasal processes It is composed of – a) Labial component- forms PHILTRUM b) Upper jaw componentcarries 4 MAX.INCISORS c) Palatal component- forms PRIMARY PALATE 74
  • 73. Formation of definitive/ secondary palate 6th week– 2 lateral palatal shelves devp Secondary nasal septum grows 7th week– palatal shelves grow & lie vertically 2 peaks of DNA synthesis occur here: initial shelf outgrowth vertical shelf elongation 75
  • 74. 8th week Stomodeum enlarges Tongue drops Vertically inclined palatal shelves become horizontal Shelves contact each other in midline– forms sec. palate By 12th week, fusion of palatal processes is complete 76
  • 75. DEVELOPMENT OF PALATE (occlusal view) 77
  • 76. DEVELOPMENT OF PALATE (frontal view) 78
  • 77. THEORIES OF PALATAL SHELF ELEVATION : EXTRINSIC FORCES Descent of tongue Myoneural activity with in tongue Shelves pushed up by tongue Mouth opening reflexes 79
  • 78. INTRINSIC FORCES  Hydration and polymerisation of intercellular substance  Differential growth on one side of palatal shelf  Turgor produced by build up of HYALURONIC ACID  SEROTONIN release from neural tissue.  ACCUMULATION of HYALURONIC ACID  Mesenchymal cell biosynthetic activity  Changing amounts of GLYCOSAMINOGLYCANS(GAG) 80
  • 79. Palatal clefts Defective fusion of various components of palate Causes: a. b. c. d. e. f. g. Defective shelf fusion Failure of shelves to elevate Failure of tongue to drop from b/w shelves Smallness of shelves Inhibition of fusion process itself Delayed elevation of shelves Failure of medial edge epithelial cell death 81
  • 80. Formation of organ systems especially the pharyngeal arches and palate 28th – 38th day – Primary palate  Cleft lip &/or palate and other Facial Clefts 42nd -55th day – Secondary palate  Cleft palate 82
  • 81. Prenatal development of maxilla Maxilla arises from a single centre of ossification in the mesenchyme of the maxillary process of the 1st arch No primary cartilage exists in the maxillary process Centre of ossification is associated with the cartilage of nasal capsule 83
  • 82. Development of maxilla The centre of ossification appears in the angle between the division of an nerve (i.e. where the anteriosuperior dental nerve is given of from the inferior orbital nerve) just above the canine tooth dental lamina 84
  • 83. Developing elements of maxilla Neural Alveolar Zygomatic Palatal Cartilaginous 85
  • 84. As a result of bone deposition --a bony trough forms for the infra orbital nerve From this trough a bony downward extension forms the lateral alveolar plate for the maxillary tooth germs Ossification spreads in to the palatine process to form hard palate The medial alveolar plate develops from the junction of the palatal process & main body of the forming maxilla This plate together with its lateral counterpart forms a trough of bone around the maxillary tooth germs, which eventually become enclosed in bony crypts 86
  • 85. Development of mandible Derived from ossification of an osteogenic membrane at 36 to 38 days of development At 6th week, a single ossifcation center for each half of mandible arises at bifurcation of inferior alveolar nerve 87
  • 86. 88
  • 87. Fate of meckel’s cartilage Dorsal end ossifies to form: malleus & incus Disappears by 24th week after conception Parts transform into: sphenomandibular ant. Malleolar ligament Ventral end forms accessory endochondral ossicles 89
  • 88. b/w 10th -14th weeks, secondary accessory cartilages appear to form head of condyle part of coronoid process mental protruberance 90
  • 89. Thus mandible is membrane bone developed in relation to the nerve of the 1st arch & almost independent of Meckel’s cartilage. The mandible has neural, alveolar & muscular elements & its growth is assisted by the development of secondary cartilages 91
  • 90. Anamolies of mandible 1. Agnathia : mandible grossly deficient/ absent cause: deficiency of neural crest tissue in lower part of face 92
  • 91. Anamolies of mandible 2. Micrognathia: characteristic of Pierre robin syndrome Treacher collins syndrome Downs syndrome Turner syndrome Cause: A central dysmorphogenic mechanism of neural crest production, migration or destruction 93
  • 92. Anamolies of mandible 3. Macrognathia: prognathism inherited condition seen in hyperpituitarism 94
  • 93. Embryological basis of dental tissue genesis 4th week of intra uterine life Lined by str. squ epi i.e oral ectoderm CT cells overlying ectoderm are ectomesenchyme in origin, induce tooth devp Ruptures at 27th day of gestation 95
  • 94. Teratogenic effects of embryonic development Teratogen : any substance, agent or process that interferes with normal prenatal development resulting in one or more abnormalities in children 96
  • 95. Susceptibility to Teratogenesis 97
  • 96. Drugs /chemicals Alcohol Infections Maternal conditions Cytomegalovir Age us General health Rubella Thalidomide Diabetes Anticonvulsants Syphilis mellitus Antidepressants Toxoplasmosis Corticosteriods Varicella Radiation Exposure 98
  • 97. Conclusion…….. 99
  • 98. References…. 1. Craniofacial Development : Geoffrey H.SPERBER(2001) 2. Textbook Of Craniofacial Growth : MOYERS 3. Oral anatomy,histology & embryology 3rd edition : B.K.B.BERKOWITZ 4. Langman’s medical embryology 9th edition : T.W.SADLER 5. Scientific foundations in dentistry: COHEN 6. Fundamentals of craniofacial growth(1997) : ANDREW D.DIXON 7. Human embryology – 7th ed – Inderbir Singh 8. Ten cate’s Oral Histology – 6th ed – Antonio 9. Essentials of Facial Growth – Enlow 10. DCNA: Vol 19: (1) : 1975 100
  • 99. THANK YOU 101
  • 100. Thank you 102
  • 101. Thank you 103