Head and neck_dev_07

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Head and neck_dev_07

  1. 1. Embryology of the Head, Face and Oral Cavity Raj Gopalakrishnan B.D.S., Ph.D. Oral and Maxillofacial PathologyDept. of Diagnostic and Biological SciencesUniversity of Minnesota School of Dentistry
  2. 2. Prenatal Development Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  3. 3. Differentiation of the Morula into Blastocyst Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  4. 4. Formation of Two-Layered Embryo (2nd week of gestation) Called bilaminar germ disk Ectoderm Endoderm Pre/prochordal plate Firm union between ectodermal and endodermal cells occur at prechordal plateFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  5. 5. Formation of Three-Layered Embryo: Gastrulation (3rd week)Triploblastic embryo Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  6. 6. Formation of Three-Layered Embryo: Gastrulation (3rd week) Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  7. 7. First 3 weeks: Leads to formation of triploblastic embryoNext 3-4 weeks: differentiation of major tissues and organs includes head and face and tissues responsible for teeth development differentiation of nervous tissue from ectoderm differentiation of neural crest cells (ectoderm) differentiation of mesoderm folding of the embryo (2 planes-rostrocaudal and lateral)
  8. 8. Formation of neural tube and neural groove Neural grooveNeural tube undergoes massive expansion to form the forebrain,midbrain and hindbrain Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  9. 9. Components of the mesoderm Along the trunk paraxial mesoderm breaks up into segmented blocks called somites Each somite has: sclerotome- 2 adjacent vertebrae and disks myotome-muscle dermatome-connective tissue of the skin over the somite In the head region the paraxial mesoderm only partially fragments to form a series of numbered somatomeres which contribute to head and neck musculature Intermediate mesoderm: urogenital system Lateral plate mesoderm: connective tissue of muscle annd viscera; serous membranes of the pleura; pericardium and peritoneum; blood and lymphatic cells; cardiovascular and lympahtic systems, spleen and adrenal cortex.Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  10. 10. In the head, the neural tube undergoes massive expansion to formthe forebrain, midbrain and hindbrainThe hindbrain segments into series of eight bulges calledrhombomeres which play an important role in development of the head
  11. 11. Folding of the Embryo Head fold forms a primitive stomatodeum or oral cavity; leading to ectoderm lining the stomatodeum and the stomatodeum separated from the gut by buccopharyngeal membrane Onset of folding is at 24 days and continues till the end of week 4 Embryo just before folding (21 days) Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  12. 12. Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  13. 13. Neural Crest CellsGroup of cells separate from the neuroectoderm, migrate anddifferentiate extensively leading to formation of cranial sensoryganglia and most of the connective tissue of the headEmbryonic connective tissue elsewhere is derived form mesodermand is known as mesenchymeBut in the head it is known as ectomesenchyme because of itsorigin from neuroectodermLook up Fig 2-12 in text book for derivative of the germ layersand neural crest
  14. 14. Avian neural crest cellsFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  15. 15. Head Formation (one of the first are the occipital somites) RhombomeresFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  16. 16. Neural Crest Cell Migration Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  17. 17. Pharyngeal arches expand by proliferation of neural crest cells Forebrain (prosencephalon) Midbrain (mesencephalon) r3 Hindbrain (rhombencephalon) r5 Couly et al., 2002
  18. 18. Migration of cranial neural crest cells Anterior midbrain FNM E TG Posterior midbrain E TG Md Anterior hindbrain E TG Md Imai et al., 1996
  19. 19. Clinical CorrelationTreacher Collins Syndrome is characterized by defects ofstructures that are derived form the 1st and 2nd branchial arches andis due to failure of neural crest cells to migrate properly to thefacial region
  20. 20. Buccopharyngeal membrane ruptures at 24 to 26 days Sagittal section through a 25-day embryo Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  21. 21. Internal View of the Oral Pit at 3.5 weeks
  22. 22. 26-day embryo Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  23. 23. The pharyngeal apparatus pouch arch groove/cleft membrane 4 1 23 esophagusBranchial arches form in the pharyngeal wall (which has lateral plate mesoderm sandwichedbetween ectoderm and endoderm) as a result of lateral plate mesoderm proliferation andsubsequent migration by neural crest cells The Developing Human by Moore & Persaud
  24. 24. 3 weeks
  25. 25. Sagittal view of the branchial arches with corresponding grooves between each arch.Pharyngeal pouches are seen in the wall of the pharynx. The aortic arch vasculatureleads from the heart dorsally through the arches to the face
  26. 26. Fate of the Pharyngeal Grooves and PouchesFirst groove and pouch: external auditory meatus tympanic membrane tympanic antrum mastoid antrum pharyngotympanic or eustachian tube2nd, 3rd and 4th grooves are obliterated by overgrowth of the secondarch forming a cervical sinus – if persists forms the branchial fistulathat opens into the side of the neck extending form the tonsillar sinus2nd pouch is obliterated by development of palatine tonsil3rd pouch: dorsally forms inferior parathyroid gland ventrally forms the thymus gland by fusing with the counterpart from opposite side
  27. 27. 4th pouch: dorsal gives rise to the superior parathyroid gland ventral gives rise to the ultimobranchial body (which gives rise to the parafollicular cells of the thyroid gland)5th pouch in humans is incorporated with the 4th pouch
  28. 28. (A) Tissue from arch II and V growing towards each other (arrows) to make branchialarches and grooves disappear(B) Resulting appearance following overgrowth(C) Contribution of each pharyngeal pouch
  29. 29. Anatomy of the Branchial Arches Cartilage of 1st arch: Meckel’s Cartilage of 2nd arch: Reichert’s Other arches not named Some mesenchyme around cartilage gives rise to striated muscle Each arch also has an artery and nerve Nerve: two components (motor and sensory) Sensory nerve divides into 2 branches: 1. Posttrematic branch: covers the anterior half of the arch epithelium 2. Prettrematic: covers the posterior half of the arch epitheliumFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  30. 30. Meckel’s cartilage: Has a close relationship with thedeveloping mandible BUT DOES NOT CONTRIBUTE TO ITIndicates the position of the future mandible.The mandible develops by intramembranous ossification.The malleus and the incus develop by endochondral ossification ofthe dorsal aspect of this cartilage.Innervation: V cranial nerveReichert’s: Dorsal end: stapes and styloid process Ventral end: lesser horns of hyoid bone and superior part of the body of the hyoid boneInnervation: VII cranial nerveCartilage of the 3rd arch: inferior part of the body and greater horns of the hyoid boneCartilage of 4th and 6th arches: fuse to form the laryngeal cartilage
  31. 31. Table obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  32. 32. Aortic Vasculature Development(A) At 4 weeks the anterior vessels have passed through each branchial arch tissueand have disappeared. The pouches project laterally between each arch.(B) At 5 weeks the 3rd branchial arch vessel becomes the common carotid, whichsupplies the face by means of the internal carotid and stapedial arteries.Face, Neck and Brain are supplied by the common carotid through internal carotid.But by 7 weeks the circulation of face and neck shifts from the internal carotid toexternal carotid. The internal carotid continues to supply the brain.
  33. 33. Details of the aortic arch changes during early development. Aortic arch vessels numbers1,2 and 5 disappear . Arch 3 becomes the common carotid artery. Arch 4 becomes thedorsal aorta and enlarges so that the common carotid arises from the aorta. Arch 6 becomesthe right and left pulmonary arteries
  34. 34. Shift in the vascular supply to the face(A) Face and brain are supplied first by the internal carotid artery(B) Facial vessels detach from the internal carotid and attach to theexternal carotid
  35. 35. Muscle cells in the first arch become apparentduring the 5th week and begin to spread withinthe mandibular arch into each muscle site’sorigin in the 6th and 7th week. These form themuscles of mastication – masseter, medialpterygoid, lateral pterygoid and temporalismuscle. They all relate to the developing mandibleBy 7 weeks the muscles of 2nd arch growupward to form the muscles of face.As these muscles grow and expand theyforms sheet over the face and forms themuscles of facial expression
  36. 36. Masticatory muscles of the mandibular archFacial muscles grow fromthe 2nd branchial arch to coverthe face, scalp and posteriorto the ear
  37. 37. Cranial Nerves growing into Branchial Arches
  38. 38. Cartilages derived from thebranchial archesArch 1: Meckels cartilage and incusArch 2: Stapes, stylohyoid and lesserhyoidArch 3: Greater hyoidArch 4 and 6 thyroid andlaryngeal cartilage
  39. 39. Anomalies of the head and neck •Congenital auricular sinuses and cysts •Branchial cysts •Branchial sinuses •Branchial fistulaDermatlas •Branchial vestiges (cartilaginous or bony remnants) •Branchial cysts Dermatlas
  40. 40. Apparent fusion of facial processes by True fusion of facial processes byelimination of furrows breakdown of surface epithelium Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  41. 41. Development of the FaceThe face develops between the 24th and 38th days of gestationOn 24th day, the 1st branchial arch divides into maxillary andmandibular arches Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  42. 42. Frontonasal processFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  43. 43. Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  44. 44. Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  45. 45. Formation of the LipsMiddle portion of the upper lip: Formed by the fusion of the medialnasal process of both sides along with the frontonasal processLateral portion of the upper lip: Fusion of the maxillary processesof each side and medial nasal processLower lip: Formed by the fusion of the two mandibular processesUnusual fusion between maxillary process and lateral nasal processleading to canalization and formation of the nasolacrimal duct
  46. 46. Human embryo at 7 weeks Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  47. 47. Cleft Lip
  48. 48. Pituitary Gland DevelopmentEctodermal in origin and develops from 2 sources:1. An upgrowth from the ectodermal roof of the stomatodeum called hypophysial diverticulum (Rathke’s Pouch) - adenohypophysis2. A downgrowth from the neuroectoderm of the diencephalon called the neurohypophysial diverticulum – neurohypophysisDuring the 4th week of development, a hypophysial diverticulum(Rathke’s pouch) projects from the roof of the stomatodeum and liesadjacent to the floor (ventral wall) of the diencephalon. By the 5thweek, this pouch has elongated and has become constrictedat its attachment to the oral epithelium and is in contact with theinfundibulum (derived from the neurohypophysis)
  49. 49. Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  50. 50. Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  51. 51. Derivation and Terminology of the Pituitary Gland Oral Ectoderm Adenohypophysis Pars distalis (hypophysial diverticulum (glandular portion) Pars tuberalis from roof of stomodeum) Pars intermedia Neuroectoderm Neurohypophysis Pars nervosa (neurohypophysial (nervous portion) Infundibular stem diverticulum from Median eminence floor of diencephalon)Clinical Significance: Craniopharyngiomas develop from remnantsof stalk of hypophysial diverticulum (in pharynx of sphenoid bone)
  52. 52. Formation of the palate (weeks 7 to 9)Palate develops from the primary palate and the secondary palateThe primary palate develops at about 28 days of gestationPrimary palate develops from the frontonasal and medial nasalprocesses and eventually forms the premaxillary portion of the maxillaThe secondary palate develops between 7th and 8th week of gestationand completes in the 3rd monthThe critical period of palate development is from the end of 6th weektill the beginning of 9th week
  53. 53. Formation of the secondary palate(starts between 7 to 8 weeks and completed around 3 months) Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  54. 54. Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  55. 55. Cleft Palate
  56. 56. Formation of the TongueThe tongue begins to develop at about 4 weeks. The oral part (anteriortwo-thirds) develops from two distal tongue buds (lateral lingualswellings) and a median tongue bud (tuberculum impar) [1st branchialarch].Innervation: V nerveThe pharyngeal part develops from the copula and the hypobranchialeminence [2nd, 3rd and 4th branchial arches].Innervation: IX cranial nerveThe line of fusion of the oral and pharyngeal parts of the tongue isroughly indicated in the adult by a V-shaped line called the terminalsulcus.At the apex of the terminal sulcus is the foramen cecum.Muscles of the tongue develop form the occipital somites andinnervated by hypoglossal nerve
  57. 57. Lingual swelling Tuberculum imparFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  58. 58. The lingual papillae appear by the end of 8th weekVallate and foliate papillae appear first, fungiform andfiliform (10-11 weeks) papillae appear laterTaste buds develop during the 11 to 13 weeks by inductiveinteraction between epithelial cells of the tongue and invadinggustatory nerve cells from chorda tympani, glossopharyngealand vagus nerves
  59. 59. Thyroid gland development (4 to 7 weeks)Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
  60. 60. Lingual thyroidThyroglossal duct cyst
  61. 61. Development of Jaw Bones Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  62. 62. Development of MandibleFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  63. 63. Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  64. 64. Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  65. 65. Fate of Meckel’s CartilagePosterior – malleus of the inner earSphenomandibular ligamentAnteriorly, may contribute to mandibleby endochondral ossification (some evidence)Rest are resorbed completely
  66. 66. Secondary CartilagesThree secondary (growth) cartilages govern further growth ofmandible until birth1. Condylar cartilage (most important)2. Coronoid cartilage3. Symphysial cartilage
  67. 67. Appears during 12th week and occupies most of the ramus and is quickly ossified by endochondral ossification, with a very thin layer of cartilage present in the condylar head. This remnant persists until 2nd decade of life and is important for growth of mandibleAppears at 4 months anddisappears immediately Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
  68. 68. Development of MaxillaDevelops from one center of ossification in maxillary process ofthe 1st branchial archCenter of ossification is angle between the divisions where theanterosuperior dental nerve is given off from inferior orbital nervefrom where it spreads posteriorly, anteriorly and superiorlyNo arch cartilage is present, so maxilla develops in closeassociation with the nasal cartilageOne secondary cartilage also contributes to maxilladevelopment: zygomatic cartilage

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