Development of the Face, Oral Cavity & Pharyngeal arches

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Development of the Face, Oral Cavity & Pharyngeal arches - D Pillay

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Development of the Face, Oral Cavity & Pharyngeal arches

  1. 1. Development of theFace, Oral Cavity &Pharyngeal arches DS PILLAY ROOM 2P24
  2. 2. Development of theFace
  3. 3. • The development of the face occurs mainly between 4 – 8 weeks• The lower jaw (mandible) is the first to form (4th week)• The facial proportions develop during the fetal period (9th week to birth)• During infancy & childhood, following the development of teeth and paranasal sinuses, the facial skeleton increases in size and contribute to the definitive shape of the face
  4. 4. Embryo at 4 - 5 weeks (Lateral view)
  5. 5. Early in the 4th week, five primordial swellingsconsisting primarily of neural crest-derivedmesenchyme appear around the stomodeum and playan important role in the development of face 1 Frontonasal prominence 2 Maxillary prominences 2 Mandibular prominences Stomodeum
  6. 6. • The single frontonasal prominence ventral to the forebrain• The paired maxillary prominences develop from the cranial part of first pharyngeal arch• The paired mandibular prominences develop from the caudal part of first pharyngeal arch Lateral view
  7. 7. • The mesoderm of the five prominences is continuous with each other• There is no internal division corresponding to the grooves demarcating the prominences externally
  8. 8. Stomodeum• An ectoderm lined depression• Separated from the primitive pharynx by the buccopharyngeal (oropharyngeal) membrane• The membrane later breaks down and stomodeum opens into the pharynx Forms the vestibule of the oral cavity
  9. 9. • By the end of 4th week, bilateral oval-shaped ectodermal thickenings called ‘nasal placodes’ appear on each side of the lower part of the Frontonasal frontonasal prominence prominence• Nasal placodes are primordia of the nose and nasal cavities.
  10. 10. • Mesenchymal cells proliferate at the margin of the placodes and produce horse-shoe shaped swellings around these.• The sides of these swellings are called ‘medial’ and ‘lateral’ nasal prominences• The placodes now lie in the floor of a depression called ‘nasal pits’ Each lateral nasal prominence is separated from the maxillary swelling by nasolacrimal groove
  11. 11. • The maxillary prominences continue to increase in size and:• Laterally, merge with the mandibular prominences to form the cheek• Medially, compress the medial nasal prominences toward the midline and finally fuses with these to form the upper lip. The upper lip is formed by the two medial nasal prominences & the two maxillary prominences
  12. 12. The medial nasal swellingsenlarge, grow medially andmerge with each other inthe midline to form theintermaxillary segment Human embryo: 7 weeks
  13. 13. Intermaxillary SegmentGives rise to the:• Philtrum of lip• Premaxillary part of the maxilla, that bears the upper 4 incisors and the associated gums• Primary palate (region of hard palate just posterior to the upper incisors)
  14. 14. The mesenchyme fromthe 1st & 2nd pairs ofpharyngeal archesinvade the facialprominences and giverise to the muscles ofmastication and musclesof facial expressionrespectively Besides the fleshy derivatives, the facial prominences also give rise to bones of the facial skeleton
  15. 15. Derivatives of Facial ComponentsThe frontonasalprominence forms the: Forehead and the bridgeof the nose Frontal and nasal bonesThe maxillary prominences form the: Upper cheek regions and most of the upper lip Maxilla, zygomatic bone, secondary palate
  16. 16. The mandibularprominences fuse andform the: Chin, lower lip, andlower cheek regions MandibleThe lateral nasal prominences form the alae ofthe noseThe medial nasal prominences fuse and form theintermaxillary segment
  17. 17. Development of the Nasal Cavity
  18. 18. • With the formation of the medial and lateral nasal prominences, the nasal placodes lie in the floor of depressions called the nasal pits• By the end of 6th week, nasal pits deepen and form nasal sacs• Each nasal sac grows dorsocaudally, ventral to the developing brain
  19. 19. • Initially the nasal sacs are separated from the oral cavity by oronasal membrane.• The oronasal membrane ruptures by the 7th week, communicating the primitive nasal cavities with the oral cavity
  20. 20. • These communications are called the primitive choanae and are located posterior to the primary palate• After the development of the secondary palate, the choanae change their position and become located at the junction of nasal cavity and the pharynx
  21. 21. • The nasal septum develops as a downgrowth from the internal parts of merged medial nasal prominences• Fuses with the palatine process in 9-12 weeks, superior to the hard palate primordium
  22. 22. • The superior, middle and inferior conchae develop on the lateral wall of each nasal cavity• The ectodermal epithelium in the roof of each nasal cavity becomes specialized as the olfactory epithelium
  23. 23. • The olfactory cells of the olfactory epithelium give origin to olfactory nerve fibers that grow into the olfactory bulb
  24. 24. Nasolacrimal duct• Develops from a rod-like thickening of the ectoderm in the floor of the nasolacrimal groove• This solid cord of cells separates from the surface ectoderm and lies in the underlying mesenchyme• The cord gets canalized to form the nasolacrimal duct• The cranial end of the duct expands to form the lacrimal sac• The caudal end opens into the inferior meatus of the nasal cavity• The duct is usually becomes completely patent only after birth• Failure of complete canalization of the duct leads to atresia of the duct (seen in about 6% of newborn infants)
  25. 25. Development of palate (palatogenesis)
  26. 26. Palatogenesis• Begins at the end of the 5th week• Gets completed by the end of the 12th week• The most critical period for the development of palate is from the end of 6th week to the beginning of 9th weekThe palate develops from two primordia: • The Primary palate • The Secondary palate
  27. 27. The Primary Palate• Begins to develop:  Early in the 6th week  From the deep part of the intermaxillary segment, as median palatine process• Lies behind the premaxillary part of the maxilla• Fuses with the developing secondary palate
  28. 28. The primary palate represents only a small part lying anterior to the incisive fossa, of the adult hard palate Primary palateHard palate Secondary palate Soft palate
  29. 29. The Secondary Palate• Is the primordia of hard and soft palate posterior to the incisive fossa• Begins to develop:  Early in the 6th week  From the internal aspect of the maxillary processes, as lateral palatine process
  30. 30. • In the beginning, the lateral palatine processes project inferomedially on each side of the tongue• With the development of the jaws, the tongue moves inferiorly.• During 7th & 8th weeks, the lateral palatine processes elongate and ascend to a horizontal position above the tongue Tongue
  31. 31. • Gradually the lateral palatine processes:  Grow medially and fuse in the median plane  Also fuse with the: • Posterior part of the primary palate & nasal septum
  32. 32. • Fusion with the nasal septum begins anteriorly during 9th week, extends posteriorly and is completed by 12th week Bone develops in the anterior part to form the hard palate. The posterior part develops as muscular soft palate
  33. 33. Changes in Face during Fetal period• Mainly result from changes in the proportion & relative positioning of facial structures• In early fetal period the nose is flat and mandible underdeveloped. They attain their characteristic form during fetal period• The enlargement of brain results in the formation of a prominent forehead• Eyes initially appear on each side of frontonasal prominence move medially• Ears first appear on lower portion of lower jaw, grow in upper direction to the level of the eyes
  34. 34. DEVELOPMENT OF 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
  35. 35. Lingual swellingTuberculum impar
  36. 36. Pharyngeal Arch Nerve Muscles Skeleton1. Mandibular Trigeminal: Mastication; Premaxilla, maxilla,(maxillary ,mandibular maxillay & mylohyoid; anterior zygomatic bone,part processes) mandibular belly of digastric, of temporal bone, divisions tensor palatine, tensor Meckel’s cartilage, tympani mandible malleus, incus,anterior ligament of malleus, sphenomadibular lig.2. Hyoid Facial n Facial expression, Stapes, styloid posterior belly of process, stylohyoid digastric, stylohyoid, ligament, lesser horn stapedius & upper portion of body of hyoid3. Glossopharyngeal Stylopharyngeus Greater horn & lower portion of body of hyoid bone4-6 Vagus Cricothyroid, levator Laryngeal cartilages Superior laryngeal palatine, constrictors (n to 4th arch) of pharynx Recurrent laryngeal (n to 6 Intrinsic m. of larynx arch)
  37. 37. 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
  38. 38. 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
  39. 39. Anomalies related toFace, Nose & Palate
  40. 40. Facial clefts Failure of the embryonic facial prominences to fuse properly• May be unilateral or bilateral• May involve: Lead to  Lips only: Cleft lip difficulty in  Palate only: Cleft palate breathing feeding  Lip & palate: Cleft lip & palate sucking  Region of nasolacrimal swallowing groove: Facial clefts & speech
  41. 41. • Median cleft lip: results from failure of the medial nasal prominences to merge and form the intermaxillary segments• Unilateral cleft lip: result from failure of the maxillary Median Cleft lip prominence to merge with the medial nasal prominence on the affected side• Bilateral cleft lip: results due to Unilateral cleft lip failure of maxillary prominences to meet and unite with the medial nasal prominences on both sides Bilateral cleft lip
  42. 42. 2. Oblique facial cleft: results from failure of the maxillary prominence to fuse with the lateral nasal prominence3. Cleft palate leaves the nasal and oral cavities connected & results in nursing problem for Oblique facial cleft the new bornMay be: Anterior/posterior to incisive foramen Unilateral/bilateral Isolated/associated with cleft lips Cleft lip, cleft jaw & cleft palate
  43. 43. Cleft lip coupled with clefts of the anterior palate or entire palate.
  44. 44. • Gnathochisis- failure of central fusion of mandibular prominences• Micrognathia-underdevelopment of lower jaw, incorrect positioning of ear.• Agnathia- total lack of development of lower jaw & incorrect positioning of ear.• Failure of maxillary prominence to fuse with median nasal prominence results in unilateral or bilateral cleft palate
  45. 45. SUMMARY OF STRUCTURES CONTRIBUTING TO FORMATION OF THE FACEPROMINENCE STRUCTURES FORMEDFrontonasal* Forehead, bridge of nose, medial and lateral nasal prominencesMaxillary Cheeks, lateral portion of upper lipMedial nasal Philtrum of upper lip, crest & tip of noseLateral nasal Alae of noseMandibular Lower lip
  46. 46. What matters most is how you see yourself … Thank U & Good luck

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