Branchial pharyngeal arches_concise

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  • 1. Head and Neck Embryology R. Dale Reynolds University of Texas at Houston Plastic and Reconstructive Surgery
  • 2. Branchial and Pharyngeal Arches
    • Fourth week
    • Neural crest cells
      • Most skeletal and connective tissue in H&N
    • Numbered cranial  caudal
    • Four well-defined pairs visible externally
    • Fifth and sixth rudimentary
    • Separated by grooves
  • 3. Branchial and Pharyngeal Arches
    • First = Mandibular
      • Mandibular Prominence  jaw
      • Maxillary Prominence  maxilla/zyg/temp
    • Second = Hyoid
  • 4.  
  • 5. Branchial and Pharyngeal Arches
    • Fate
      • Typical arch contains
        • Aortic arch
        • Cartilaginous rod (skeleton of arch)
        • Muscular component
        • Nerve
  • 6. Branchial and Pharyngeal Arches
  • 7. Pharyngeal Pouches
    • First
      • Tubotympanic recess  tympanic membrane
      • Connects with pharynx  eustachian tube
    • Second
      • Palatine tonsil, tonsillar fossa
    • Third
      • Inferior parathyroid gland
      • Thymus
  • 8. Pharyngeal Pouches
    • Fourth
      • Superior parathyroid gland
      • Ultimobranchial body fuses with thyroid
      • Parafollicular C cells  calcitonin
    • Fifth
      • Rudimentary
  • 9.  
  • 10. Pharyngeal Pouches
  • 11. Branchial or Pharyngeal Grooves
    • Four on each side
    • Separate branchial or pharyngeal arches
    • First  External acoustic meatus
    • Others lie in depression (cervical sinus) which obliterates
  • 12. Branchial or Pharyngeal Grooves
  • 13. Branchial or Pharyngeal Membranes
    • Only one pair contribute to adult structures
    • First  tympanic membrane
  • 14. Branchial and Pharyngeal Anomalies
    • Congenital Auricular Sinuses and Cysts
      • Small sinuses (pits) and cysts commonly found in a triangular area of skin anterior to the ear
      • May be remnant of branchial or pharyngeal groove
  • 15. Branchial and Pharyngeal Anomalies
    • Branchial Sinuses
      • Lateral cervical: Uncommon, open externally (neck), failure of second groove or cervical sinus to obliterate
      • External branchial sinuses: Mucous d/c from infant’s neck, bilateral in 10%
      • Internal branchial sinuses: Rare, persistent second pouch, open into intratonsillar cleft
  • 16. Branchial and Pharyngeal Anomalies
    • Branchial Fistula
      • Connection between intratonsillar cleft and neck
      • Runs between internal and external carotids
      • Persistent second groove and second pouch
  • 17. Branchial and Pharyngeal Anomalies
    • Branchial Cysts
      • Develop along anterior border of sternocleidomastoid
      • Most inferior to angle of mandible
      • Often present in adulthood
      • Remnants of cervical sinus and/or second groove
  • 18. Branchial and Pharyngeal Anomalies
    • Branchial Vestiges
      • Cartilaginous or bony remnants
      • Usually anterior to inferior third of sternocleidomastoid
  • 19. Branchial and Pharyngeal Anomalies
    • First Arch Syndrome
    • First branchial or pharyngeal arch
      • Treacher Collins syndrome
        • Malar hypoplasia, down-slanting of palpebral fissures, lower eyelid colobomas, ear deformations
      • Pierre Robin syndrome
        • Hypoplasia of the mandible, cleft palate, and defects of the eye and ear
  • 20. Branchial and Pharyngeal Anomalies
    • DiGeorge Syndrome (Congenital Thymic and Parathyroid Aplasia)
      • Failure of third and fourth pouches to differentiate into thymus and parathyroid glands
      • Hypoparathyroidism
      • Increased incidence of infections
      • Shortened philtrum
      • Low-set notched ears
      • Nasal clefts
      • Thyroid hypoplasia
      • Cardiac anomalies
  • 21. Branchial and Pharyngeal Anomalies
    • Accessory Thymic Tissue
      • Isolated portion of thymic tissue may persist
      • Often in close association with inferior parathyroid gland
  • 22. Branchial and Pharyngeal Anomalies
    • Ectopic Parathyroid Gland
      • Variable in number (2-6) and location
      • Superior more constant than inferior
      • Thyroid to thorax
    • Absence of Parathroid Gland
  • 23. Thyroid Gland
    • Begins as thickening in the floor of the pharynx
    • Forms an outpouching (thyroid diverticulum)
    • Descends into neck passing ventral to hyoid bone and laryngeal cartilages
    • Connected to tongue by thryoglossal duct at foramen cecum
  • 24. Thyroid Gland
    • Isthmus connects right and left lobes
    • Thyroglossal duct degenerates
    • Blind pit marks the foramen cecum
    • Pyramidal lobe extends superiorly from the isthmus in fifty per cent
  • 25. Thyroid Anomalies
    • Thyroglossal Duct Cysts and Sinuses
      • May form anywhere along the course followed by the thyroglossal duct
      • Most seen by 5 yo
      • Asymptomatic unless infected
      • Midline, painless, moveable neck mass
      • Sinuses are open, cysts are closed
  • 26. Thyroid Anomalies
    • Ectopic Thyroid Gland
      • Lingual thyroid
        • Result of failure to descend
        • Often only thyroid tissue present
      • Accessory thyroid tissue
        • Tongue
        • Neck, superior or lateral to thyroid
  • 27. Tongue
    • General
      • Merged distal tongue buds  anterior 2/3
      • Copula and hypobranchial eminence  posterior 1/3
      • Terminal sulcus divides anterior and posterior
    • Taste buds
      • Most are filiform papillae and are sensitive to touch
    • Muscles
      • Supplied by XII except for palatoglossus (X)
  • 28. Tongue
    • Nerves
      • Sensory for anterior 2/3 is from V 3 (lingual)
      • Chorda tympani (VII) taste buds for anterior 2/3 (except for vallate papillae supplied by IX)
      • IX supplies posterior 1/3
      • X (Superior Laryngeal) supplies area around epiglottis
  • 29. Tongue
    • Taste buds
      • Most are filiform papillae and are sensitive to touch
  • 30. Tongue Anomalies
    • Lingual cysts and Fistulas
      • Persistence of thyroglossal duct open to foramen cecum
    • Ankyloglosia (Tongue-Tie)
      • Short frenulum to tip, stretches with time
    • Macroglossia
      • Usually from muscular hypertrophy or lymphangioma
    • Microglossia
      • Associate with micrognathia and limb defects (Hanhart’s syndrome)
    • Bifid or Cleft Tongue (Glossochisis)
      • Incomplete fusion of distal tongue buds  deep median sulcus
  • 31. Ear
    • Three anterior hillocks of the first branchial arch form the tragus, helical crus, and superior helix
    • Three posterior hillocks of the second branchial arch form the antihelix, antitragus, and lobule
    • First branchial groove forms external auditory meatus
    • Microtia
      • 1:6000-8000 births
      • Associated with hemifacial microsomia
    • Nerves
      • Great auricular (C2, C3)  lower lateral/lower cranial
      • Auriculotemporal (V 3 )  superolateral/ anterior and superior external auditory canal
      • Lesser occipital  superior cranial
      • Arnold’s (X)  concha / posterior auditory canal (referred oropharyngeal pain)
  • 32. Ear
  • 33. Face
    • Stomodeum is primitive mouth
    • Five facial primordia appear as prominences around stomodeum
      • Single fronto(  forehead)nasal{  most of nose(except septum/alae)} prominence  optic vesicles  eyes
      • Paired maxillary prominences  lateral upper lip, most of maxilla, secondary palate
      • Paired mandibular prominences  chin, lower lip, lower cheek
  • 34. Face
    • Mandible forms first
    • Nasal placodes  nasal pits
    • Six auricular hillocks  ear
    • Epithelial cord canalizes in nasolacrimal groove  nasolacrimal duct
      • Atresia if canalization fails
  • 35. Face
    • Lateral nasal prominence  nasal alae
    • Medial nasal prominences merge  intermaxillary segment  philtrum of lip, premaxilla (gum), primary palate, nasal septum
    • Second arch  muscles of facial expression (VII)
    • First arch  muscles of mastication (V)
  • 36. Face
    • Labiogingival lamina  lips and gingivae, lingual frenulum
    • Changes
      • Early fetal period: Flat nose and underdeveloped mandible
      • Enlarging brain: Prominent forehead, medial movement of eyes and external ears rise
  • 37. Nasal Cavities
    • Nasal placodes  nasal pits  deepening  nasal sacs
    • Oronasal membrane separates the oral cavity from the nasal sacs
    • Membrane ruptures  primitive chonae (opening b/w nasal cavity and nasopharynx)
  • 38. Nasal Cavities
    • Olfactory system
      • Ectodermal epithelium in the roof of each nasal cavity  specialized  olfactory epithelium
      • Some epithelial cells  olfactory receptors (axons become olfactory nerve) and grow into bulbs of the brain
  • 39. Nasal Cavities
    • Paranasal sinuses
      • From outgrowths of nasal cavity walls  pneumatic (air-filled) extensions of the nasal cavities in adjacent bones
      • Original openings of the outgrowths persist as the orifices of the adult sinuses
      • Most are rudimentary in newborns
        • Frontal sinuses are visible by seven
        • Sphenoidal sinuses usually evident by two
      • Vomeronasal cartilage  narrow cartilage strips between the inferior edge of the cartilage of nasal septum and vomer
  • 40. Palate
    • Palatogenesis from 5 th – 12 th week
    • Primary Palate
      • Median palatine process begins to develop from deep intermaxillary segment of maxilla
      • Primary palate forms the premaxillary part of the maxilla
      • Represents a small part of the adult hard palate (anterior to the incisive foramen that lodges the incisor teeth)
  • 41. Palate
    • Secondary Palate
      • Primordium of hard and soft palates that extend posteriorly from the incisive foramen
      • Shelf-like structures called lateral palatine processes (palatine shelves) project inferiomedially on each side of the tongue
  • 42. Palate
    • Secondary Palate
      • Shelves elongate and ascend to a horizontal position superior to the tongue
      • Shelves fuse in a median plane with nasal septum and posterior primary palate
      • Elevation to the horizontal position is thought to be caused by the intrinsic shelf elevating force by hydration of hyaluronic acid in the shelves
  • 43. Palate
    • Secondary Palate
      • Nasal septum develops from downgrowths of merged medial nasal prominences
      • Fusion between nasal septum and palatine processes proceeds anteriorly to posteriorly
  • 44. Palate
    • Secondary Palate
      • Bone develops in primary palate forming the premaxillary part of the maxilla which lodges between the incisor teeth
      • Bone extends from the maxillae and palatine bones in to the lateral palatine processes to form the hard palate
  • 45. Palate
    • Secondary Palate
      • Posterior aspects do not ossify
      • Extend posteriorly beyond nasal septum and fuse to form the soft palate and uvula
      • Palatine raphe permanently indicates the line of fusion of the lateral palatine processes
  • 46. Palate
    • Secondary Palate
      • Small nasopalatine canal persists between premaxilla and palatine processes as incisive foramen (openings for incisive canals)
  • 47. Clefts
      • Lip and palate
        • Upper lip and anterior maxilla with or without hard and soft palate
        • Hard and soft palate
      • Complete posterior (to incisive foramen) palate
      • Anterior cleft anomalies
        • Cleft lip, with or without a cleft of the alveolar part of the maxilla
        • Result from deficiency of mesenchyme in the maxillary prominences and intermaxillary segment
  • 48. Clefts
    • Posterior cleft anomalies
      • Clefts of secondary or posterior palate that extend through the soft and hard palate to the incisive foramen
      • Caused by defective development of the secondary palate and result from the growth distortions of the lateral palatine processes (shelves) which prevent their medial migration and fusion
  • 49. Clefts
      • Lip
        • 1:1000 births, 70% male,
        • Caucasion>Asian>Hispanic>AA
        • Notches on vermilion border to alveolar maxilla
  • 50. Clefts
      • Unilateral
        • Failure of maxillary prominence on affected side to unite with merged medial nasal prominences
        • Consequence of failure of mesenchymal masses to merge and the mesenchyme to proliferate and smooth out the overlying epithelium
        • Results in persistent labial groove
        • Epithelium in the labial groove stretches and tissues of the floor breakdown
        • Lip is divided into medial and lateral parts
        • Bridge of tissue (Simonart’s band) joins parts of incomplete cleft lip
  • 51. Unilateral cleft lip
  • 52. Clefts
      • Bilateral
        • Failure of mesenchymal masses in the maxillary prominences to met and unite with the merged medial nasal prominences
        • Epithelium in both labial grooves becomes stretched and breaks down
        • May have varying degrees of defects on each side
        • When there is a complete bilateral cleft of the lip and alveolar part of the maxilla, the intermaxillary segment hangs free and projects anteriorly
        • These defects are deforming because of loss of continuity with the orbicularis oris muscle which purses the lips
  • 53. Clefts
      • Median (rare)
        • Upper
          • Mesenchymal deficiency causing partial or complete failure of medial nasal prominences to merge and form the intermaxillary segment
          • Characteristic of the Mohr syndrome
        • Lower
          • Failure of mesenchymal masses in the mandibular prominences to merge completely and smooth out the embryonic cleft between them
  • 54. Clefts
      • Palate
        • +/- lip in 1:2500 births, females
        • Uvula, soft/hard palate, lip, alveolar maxilla
        • Failure of mesenchymal masses in lateral palatine processes (shelves) to fuse with each other, the nasal septum and posterior margin of the median palatine process
  • 55. Clefts
      • Palate (divided by incisive foramen)
        • Anterior
          • Failure of mesenchymal masses in lateral palatine masses to fuse with primary palate
        • Posterior
          • Failure of mesenchymal masses in lateral palatine masses to fuse with nasal septum
        • Both
          • Failure of mesenchymal masses in lateral palatine masses to fuse with each other, primary palate or nasal septum
  • 56. Craniofacial clefts
    • 1.4-5.1:100,000
    • Numbered 0-14 (sum=14)
      • 0-7 are facial
      • 8-14 are cranial
    • Number 7 is least rare (1:5600) =hemifacial microsomia (hypoplasia of mandibular ramus, hypoplasia of midface, others) associated with Goldenhar syndrome
    • Bilateral 6,7,8 is complete form of Treacher-Collins
  • 57. Others
    • Facial clefts
    • Macrostomia
    • Microstomia
    • Nasal
    • Single nostril
    • Bifid nose
    • Absence
  • 58.  
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  • 66. END