Pre-natal facial growth Dr. Nabil Al-Zubair


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Pre-natal facial growth Dr. Nabil Al-Zubair

  1. 1. Dr. Nabil Al-ZubairPRE-NATAL FACIAL GROWTH
  2. 2. IntroductionGrowth & developmentof an individualcan be divided into TWO periods:1. Pre-natal period 2. Post-natal period
  3. 3. can be ArbitrarilyDivided into three periods:1. Period of ovum2. Period of embryo3. Period of fetus
  4. 4. 1. Period of ovumExtendsTime of Fertilization Two weeksDuring this periodThe Cleavage of the OvumThe Attachment of the Ovum to the Intra-uterine WallOccurs
  5. 5. 1-7 wks2. Period of embryoExtendsFourteen day Fifty sixth dayof intra-uterine lifeThe major part of the development of the facial &cranial region occursDuring this period
  6. 6. 3. Period of fetusExtendsTill birthFifty sixth dayDuring this periodAccelerated growth of the cranio-facial structuresresulting in an increase in their sizeChange in proportion b/w the various structures also occursIn addition
  8. 8. Prenatal growth of Cranial Base
  9. 9. The earliest evidenceseen inpost or late somitic period(4th – 8th week of intra-uterine life)
  10. 10. • Thus a capsule is formedaround the brain calledEctomenix orEctomeningeal capsuleMesenchymal tissue condensearound the developing brainCARTILAGE40th dayBONEChondro-ossification
  11. 11. Flexure of the cranial base‫التواء‬During the embryonic & early fetal periodin the regionb/wPituitary fossa&Spheno-occipital junctioncranial base flexed
  12. 12. Flexure of the cranial baseaccompanied by a correspondingFlexure of the developing Brain Stemcranial base flexedSpinal chord & Foramen magnumdirecteddownwardsduring the early stages of developmentdirected backwards
  13. 13. Flexure of the cranial base• Downwards directed foramenmagnum is an adaptation seenin man who, unlike animals,(1) Stand erect• Another consequence of theflexure is(2) The predominant downwardrather than forwarddisplacement of the faceduring its growth from the cranialbase
  15. 15. on the ventral aspect of the embryoVentral aspect Dorsal aspectAbout the 4th week of intra-uterine life(1) the developing brainTwo prominentBULGES ‫انتفاخ‬(2)
  16. 16. BUCCO-PHARYNGEALMEMBRANESTOMODEUMBRAINIIIBULGESseparated byPrimitive oral cavitywhich separates it from the foregutformed byThe floorFOREGUT
  17. 17. STOMODEUMBRAINIIIESOPHAGEOUSPHARYNGEAL ARCHESFOREGUTLaid down on the lateral & ventral aspectscranialmostLies in close approximationwithSTOMODEUM
  18. 18. PHARYNGEAL ARCHESInitially sixFifth one disappears as soon as it is formedSeparatedBRANCHIAL GROOVES
  19. 19. Mid-sagittal sectionBRAINHEARTIIICORDCARDIACBULGEFull-face view 4-w embryoform in the region of the future head & neckIIIBranchial archesBy aroundfive4th week of intra-uterine life
  20. 20. Mid-sagittal sectionBRAINHEARTI IICORDCARDIACBULGEFull-face view 4-w embryoEach of these arches contain:1. A central cartilage rod that forms the skeleton of the arch2. A muscular component termed as branchiomere3. A vascular component4. A neural elementIIIBranchial arches
  21. 21. Mid-sagittal sectionBRAINHEARTI IICORDCARDIACBULGEFull-face view 4-w embryoThe other arches do not have any specific namesIIIBranchial archesfirst archMANDIBULAR ARCHDevelopment ofthe naso-maxillaryregionPlays animportant role inSecond arch,HYOID ARCH.
  22. 22. Prenatal Growth of Naso-maxillary CpomlexMaxillaNosePalate
  23. 23. Mid-sagittal section of 1-m embryoFRONTONASALPROCESSSTOMODEUMBRAINPHARYNGEAL ARCHESI IIThe Mesoderm covering the developing forebrain Proliferates & forms adownward projection that Overlaps the upper part of STOMODEUM.This downward projection is calledFRONTO-NASAL PROCESS
  24. 24. MAXILLARY PROCESSSTOMODEUMwith perforating membraneCARDIACBULGEMANDIBULAR ARCHHYOID ARCH4-w/3.5mm EMBRYO• The mandibular archgives off a bud from itsdorsal end called themaxillary process
  25. 25. MAXILLARY PROCESSMANDIBULAR PROCESSCARDIACBULGEHYOID ARCHSTOMODEUMwith perforating membrane4-w/3.5mm EMBRYO• The Maxillary ProcessGROWSVentro-medio-cranialto the main part ofthe Mandibular Archwhich is now calledthe Mandibular Process
  26. 26. FRONTONASAL PROCESSMAXILLARY PROCESSMANDIBULAR PROCESSCARDIACBULGEHYOID ARCHSTOMODEUMwith perforating membrane4-w/3.5mm EMBRYOAt this stage the Primitive Mouth orStomodeumOVERLAPPEDfrom abovefrom belowon either sideMAXILLARY PROCESS
  27. 27. OPTIC PLACODECARDIAC BULGEBilateral localized thickeningsabove the stomodeum4-w/3.5mm EMBRYONASAL PLACODESsoon sink & formNASAL PITSThe ectoderm overlying thefronto-nasal processshows
  28. 28. CARDIAC BULGEThe formation of these NASAL PITSdivides the fronto-nasal processinto two parts:a. The medial nasal process &b. The lateral nasal processLateral processes willbecome Alae of NoseMedial processes form midline nose &contribute to lip, central upper jaw& primary palate4-w/3.5mm EMBRYO
  29. 29. 5.5-w/9mm EMBRYOMAXILLARY PROCESSAs the Maxillary Processundergoes Growth,The fronto-nasal processbecomes narrowso that the two NASAL PITScome closerFronto-nasal process
  30. 30. Development of Palate
  31. 31. NARISDevelopment of palate• The palate is formed bycontribution of the :a. Fronto-nasal processb. Maxillary processc. Palatal shelves given offby the maxillary processNARISINTER-MAXILLARYSEGMENTPRIMARY PALATE/ Median palatine processNARISGives rise to the premaxillaryregionForm the rest of the palate
  32. 32. Development of palate• As the PALATAL SHELVESgrow medially,Their union is prevented by thepresence of the TONGUETONGUE
  33. 33. Development of palate• Initially the developingPALATAL SHELVES growvertically downward towardsthe floor of the mouth• During the seventh week ofintra-uterine life,a transformation in the position ofthe palatal shelves occursEYEBRAINMECKEL’S CARTILAGETONGUE
  34. 34. *Site for meeting and fusion of nasal septum& palatal shelvesEYETOOTH BUDBRAINTONGUE*They change from a VERTICAL to HORIZONTALpositionMECKEL’S CARTILAGEmandibular boneTONGUELATERAL PALATINE SHELFMaxillary boneThis transformation isbelieved to take placewithin hours
  35. 35. Reasons to explain how this transformation occursa. Alteration in biochemical &physical consistency of theconnective tissue of the palatalshelvesb. Alteration in vasculature & bloodsupply of the palatal shelvesc. Appearance of intrinsic shelfforced. Rapid differential mitotic activitye. Muscular movementsf. Withdrawal of the embryonic face fromagainst the heart prominence results inslight jaw opening. This results inwithdrawal of the tongue from b/w thepalatal shelves from a vertical to ahorizontal position
  36. 36. PALATEPROXIMITYEpithelial disintegration& conversionMesenchymal continuityFUSIONEpithelial & MesenchymaldifferentiationSTEPS IN PALATAL-NASAL FUSIONby 8 ½ weeks of intra-uterine lifeThe connective tissue intermingleseparates the twonasal cavities fromeach other & the oralcavityThe mesial edges of thepalatal processes fuse withthe free lower end of nasalseptum
  37. 37. Prenatal Growth of Mandible
  38. 38. • The Meckel’s cartilage is derivedfrom the first branchial arch aroundthe 41st – 45th day of intra-uterinelife• It extends from the cartilaginousotic capsule to the midline orsymphysis & provides a templatefor guiding the growth of themandibleTONGUEMeckel’s cartilage
  39. 39. TONGUEMeckel’s cartilage• A major portion of the Meckel’scartilage DISAPPEARS duringgrowth &the remaining part develops into thefollowing structures:1. The mental ossicles2. Incus & Malleus3. Anterior ligament of malleus4. Spheno-mandibular ligamentTONGUE
  40. 40. Meckel’s cartilage• The first structures to develop in thePRIMORDIUM of the lower jaw isTHE MANDIBULAR DIVISION of thetrigeminal nerve.• This is followed by the mesenchymalcondensation forming The firstbranchial archTONGUETONGUE
  41. 41. TONGUENeurotrophic factorsOSTEOGENESISOssification centersinduceNervesingle6th week of intra-uterine lifeBIFURCATION of the inferior alveolar nerveinto mental & incisive branches
  42. 42. TONGUENeurotrophic factorsOSTEOGENESISOssification centersinduceNervesingle6th week of intra-uterine lifeBIFURCATION of the inferior alveolarnerve into mental & incisive branchesIntramembranous ossification spreads:(1) Below & around the inferior alveolar nerve & itsincisive branch & upwardsTrough
  43. 43. TONGUENeurotrophic factorsOSTEOGENESISOssification centersinduceNervesingle6th week of intra-uterine lifeBIFURCATION of the inferioralveolar nerve into mental &incisive branchesIntramembranous ossification spreads:(1) Below & around the inferior alveolarnerve & its incisive branch & upwardsTrough(2) Dorsally & ventrally froms the body & ramus of themandible
  44. 44. 7-w/19mm EMBRYOEYEFOREHEADMOUTHLOWER JAWHYOID BONEMAXILLARY PROCESSLARYNGEAL CARTILAGESFACEThe two mandibularprocesses grow medially& fuse to form the lowerlip & lower jaw
  45. 45. Thank you for listening!