Branchial arches

simple and detailed

1. PRIYONA JOHN 1ST year PG DEPARTMENT OF PAEDODONTICS & PREVENTIVE DENTISTRY BRANCHIAL ARCHES

2. CONTENTS Introduction Evolution of branchial arches. Normal development of branchial arches. Derivatives of branchial system. - First branchial arch. - Second branchial arch. - Third branchial arch. - Fourth branchial arch. -Sixth branchial arch

3. Anomalies of development of branchial arches. Branchial pouches; -Normal development of branchial pouches -First branchial pouch. -Second branchial pouch. -Third branchial pouch. -Fourth branchial pouch.

4. Branchial cleft. Molecular regulation of facial development. Anomalies of development of branchial pouches and cleft.

5. INTRODUCTION Pharyngeal arches are rod like thickenings of mesoderm present in the wall of foregut.There are six pairs of pharyngeal arches, in which the fifth one is rudimentry . Mesenchyme for the formation of the head region is derived from paraxial and lateral plate mesoderm,neural crest cells and thickened region of ectoderm known as ectodermal placodes .

6. Paraxial mesoderm The mesoderm on either side of the notochord becomes thick and is called paraxial mesoderm. The paraxial mesoderm segmented into cubical masses called somitomeres which give rise to somites . Somites:It lies on the either side of developing neural tube.

7. Lateral plate mesoderm More laterally, the mesoderm forms a thinner layer called lateral plate mesoderm.

8. Neural crest cells Pluripotent cells. Great migratory properties. Migration of cells can be translocations(resulting of dislocation of tissues)or active cell migration. Being pluripotent , display varying regional characteristics at their destination sites.

9. Neural crest cells remaining rostral and dorsal to the forebrain contribute to the leptomeninges and parts of skull. Those around mid brain form part of trigeminal ganglion. Neural crest cells migrating caudally and ventrally encounter the pharyngeal endoderm that induces formation of pharyngeal arches.

10. Many pharyngeal derivatives, including facial bones are of neural crest origin. Cells migrate within cranial paraxial mesoderm form somitomeres , which provides muscle of the face and jaw.

11. Development and evolution of branchial arches In all vertebrates, pharyngeal apparatus develops from a series of bulges found on lateral surface of head.The pharyngeal arches consists of number of embryonic cell types. Each arch has: 1.Externally covering ectoderm. 2.Internally covering endoderm between these mesenchymal filling of neural crest with central core of mesoderm.

12. Different embryonic population produce different components of the arch. Ectoderm –Epidermis and sensory neurons of epibranchial ganglia. Endoderm –Epithelial lining of the pharynx and forms the taste buds as well as the thyroid and parathyroid and thymus.

13. Neural crest cells forms –skeletal and connective tissue . Mesoderm forms musculature and endothelial cells. In all gnathostomes : First arch-jaw Second arch-hyoid apparatus More caudal arches-gills in fish and throat in amniotes.

14. Developmental basis of the evolution of the vertebrae pharynx. The transition from prochordates to vertebrates: Neural crest cells produce a key role in the evolution of vertebrate pharynx. Yet the evolution of the vertebrate pharynx was not driven exclusively by the crest, but is rather integration of signals.

15. In chick, pharyngeal arches can form and are patterned in absence of neural crest cells reflects the evolutionary history of arches. Pharyngeal segmentation is a general chordate feature. But in the presence of neural crest or more specifically ectomesenchymal crest is a vertebrate feature.

16. The one substantial difference between the vertebrates pharyngeal arches and those of prochordates is the presence of epibranchial placodes .

17. The transition from agnatha to gnathostomes . The segregation of the neural crest cells into 3 streams, each endowed with a distinct identity has been proposed as being an important event in the of gnathostomes .(Graham et al.1993) However a recent study of lamprey crest has found that even though this animal is jawless its pharyngeal crest is also organized into three.( Horigome et al.1999)

18. Transition to tetrapods Key changes occurred at caudal end of the pharynx, and they are all likely to have been driven by changes in the endoderm.

19. Normal development In the 4 th week of IUL, after establishment of the head fold, the foregut is bounded ventrally by the pericardium, dorsally by the developing brain, cranially it is first separated from stomatodeum by buccopharyngeal membrane when this membrane breaks down, the foregut open to exterior through stomatodeum .

20. The neck is formed by the elongation of the region between the stomatoduem and pericardium this is achieved partly by the descent of developing heart. However this elongation is due to the appearance of series of mesodermal thickenings in the wall of cranial most part of the foregut. These are called pharyngeal or branchial arches.

21. At this stage ; - Head is represented by bulging caused by the developing brain. - Pericardium –future thorax. - Stomatodeum –future mouth .

22. BRANCHIAL ARCH COMPONENTS Muscular components. Skeletal components. Cranial nerve. Arterial component.

23. First branchial arch Also called mandibular arch. Precursor of both maxilla and mandible. The maxilla is derived from a small maxillary prominence extending cranioventrally from much larger mandibular prominence derived from first arch.

24. Skeleton components Meckels cartilage. The ear ossicle malleus and incus . MECKELS CARTILAGE: Arises at 41 st to 45 th day of post conception. Provides template for development of mandible.

25. Most of the cartilage substance of meckels cartilage disappears in formed mandible. Mental ossicle is the only portion of the mandible derived from the meckels cartilage by endochondral ossification.

26. During further development meckels cartilage disappears expect for two small portions at its dorsal end that persist and form (head and neck of malleus ) and the body and short crus of the incus . Two ligaments: -The anterior ligament of malleus . - The sphenomandibular ligament.

27. Muscular components Originating from cranial somitomere 4. Muscles are: -Muscles of mastication. -The mylohyoid muscle. -The anterior belly of digastric . -The tensor tympani. -Tensor veli palatini .

28. Nerve of the arch. Mandibular division of trigeminal nerve. The sensory component of this nerve innervates the mandible and its covering mucosa and gingiva , the mandibular teeth, anterior two thirds of tongue, floor of mouth and skin of the lower third of face.

29. Artery of the arch The first arch artery contributes in part of the maxillary artery and part of external carotid artery.

30. SECOND BRANCHIAL ARCH Also known as hyoid arch. Cartilage of second arch is Reichert’s cartilage. REICHERTS CARTILAGE: It appears on the 45 th to 48 th days of post conception.

31. Reicherts cartilage attaches to basicranial otic capsule where it is grooved by facial nerve, it provides the remaining cartilaginous circumference to labyrinthine and tympanic segments of the facial canal.

32. Skeleton components Reicherts cartilage. Styloid process of temporal bone. The stapes. Lesser horn and cranial part of body of the hyoid bone. Stylohyoid ligament.

33. MUSCULAR COMPONENTS Muscles of second arch originates from cranial somitomere 6. Muscles are: - Stylohyoid . -Posterior belly of digastric . -Muscles of facial expression. - Stapedius .

34. Nerve of the arch : - Facial nerve. Artery of the arch : - Stapedial artery. Stapedial artery - Derived from second aortic arch. - Which disappears during fetal period, leaving foramen in stapes .

35. A Branch of internal carotid artery, the stapedial artery initially supplies the deep portion of face, an area is taken over by branches of external carotid artery once the stapedial artery disappears.

36. THIRD BRANCHIAL ARCH Skeleton components: The greater horn and the caudal part of the body of the hyoid bone. The reminder of the cartilage disappears. Muscular components: Muscles of this arch originating from cranial somitomere 7. It forms stylopharyngeus muscle.

37. Nerve of the arch Glossopharyngeal . The mucosa of the posterior third of the tongue is derived from this arch, accounting for its sensory innervation by glossopharyngeal nerve.

38. Artery of the arch Common carotid and part of internal carotid artery.

39. Neural crest tissue in the third arch forms carotid body, which first appears as a mesenchymal condensation around the third aortic arch artery. This chemoreceptor body derives nerve supply from glossopharnygeal nerve .

40. FOURTH BRANCHIAL ARCH Fourth arch forms the thyroid cartilage. Muscular components: Muscles originating from occipital somites 2 and 4.

41. It forms: - Constrictors of pharynx. - Palatopharyngeus . - Palatoglossus muscle of tongue - Levator veli palatini . - Uvular muscles of soft palate.

42. Nerve of the arch: Superior laryngeal branch of 10 th cranial nerve. Artery of the arch: Fourth arch artery Left side Right side Arch of aorta. Brachiocephalic . LEFT SIDE RIGHT SIDE

43. SIXTH PHARYNGEAL ARCH Cartilage of sixth arch probably forms cricoid and arytenoid cartilages of larynx. Muscular components: From occipital somites 1 and 2. Forms intrinsic muscles of larynx.

44. Nerve of the arch: Recurrent laryngeal branch of vagus nerve. Artery of the arch: Pulmonary arteries. Ductus arteriosus .

45. ANOMALIES OF THE BRANCHIAL ARCH Deficient development of pharyngeal arches results in syndromes that are identified according to the arches. The first and second branchial arch syndrome includes array of defects involving not only those derivatives of first and second arches and cleft but also primordia of the temporal bone.

46. Most common abnormalities are: Underdevelopment of external ear, middle ear ossicles , the condyle , the ramus , the zygomatic arch and the malar bone and the temporal bone expect for the petrous section. Muscles of mastication and facial expression are affected.

47. Clinical appearance of macrostomia and seventh cranial nerve paresis. One or more accessory auricles are present along the oro-tragal line. Necrotic facial dysplasia. Hemifacial Microsomia and Microtia . Otomandibular dysostosis . Unilateral facial agenesis.

48. Intrauterine facial necrosis. Hemignathia . Microtia syndrome. Berry Treacher Collins syndrome. Goldenhars syndrome. Hallerman Streiff syndrome. Eagle syndrome. Pierre Robin syndrome.

49. Berry Treacher Collins Syndrome Also known as mandibulofacial dysostosis . Bird like or fish like faces. Clinical features: - Hypoplasia of facial bones especially malar and mandible. -Malformation of external ear, middle and internal ear.

50. Macrostomia, high palate and abnormal position and malocclusion of teeth. Blind fistulas between angles of the ears and angles of the mouth. Facial clefts and other skeleton deformities.

51. In Germany following the administration of thalidomide to woman in the first 6 weeks of pregnancy between 1959 and 1962 at least 1000 severe cases and up to 2000 less severe cases of defects of the first and second branchial arches were observed in their offspring.

52. PHARYNGEAL POUCHES There are four pairs of pharyngeal pouches. Fifth one is rudimentry .

53. Normal development of pharyngeal pouches . In late embryonic period Dilation of the cranial end of the foregut, that lying between developing head ventrally and the developing chondrocranium rostrodorsally . It leds to formation of the primitive pharynx .

54. Then the lateral aspect of the elongated primitive pharynx project a series of pouches between the pharyngeal arches. Formation of pharyngeal/ branchial pouches.

55. Pharyngeal pouches sequentially decrease in size craniocaudally . Pharyngeal pouch is lined by foregut endoderm.

56. FIRST PHARYGEAL POUCH Pouch has ventral and dorsal surfaces. Ventral portion is obliterated by developing tongue. Dorsal diverticulum deepens laterally as the tubotympanic recess to form auditory tube. Widening of the auditory tube end into tympanum/middle ear cavity.

57. Tympanum/middle ear cavity occupied by the dorsal ends of the cartilages of the first and second pharyngeal arches that develops into ear ossicle . Tympanum maintains contact with pharynx via the auditory tube throughout life.

58. SECOND PHARNYGEAL POUCH Ventral portion obliterated by the developing tongue. The epithelial lining of pharyngeal pouch proliferates and forms buds that penetrate into surrounding mesenchyme . The buds are secondarily invaded by mesodermal tissue forming the primodium of palatine tonsils .

59. During the 3 rd and 5 th months, the tonsil is infiltrated by the lymphatic tissue. Part of the pouch remains and is found in the adult as tonsillar fossa .

60. THIRD PHARYNGEAL POUCH Thymus and inferior parathyroid gland formed from third pouch. The distal extremity has a dorsal and ventral wing. In the 5 th week, epithelium of dorsal region differentiates into inferior parathyroid gland.

61. Ventral surface epithelium differentiates from each side it migrates and forms two elongated diverticula it grows caudally into surrounding mesenchyme to form the elements of thymus gland.

62. The two thymic rudimentary from each side meets in the mid line but do not fuse, united by connective tissue. Lymphoid cells invade thymus from hemopoietic tissue during the 3 rd month of post conception .

63. Growth and development of thymus continue until puberty. In young child the thymus occupies considerable space in the thorax and lies behind the sternum and anterior to the pericardium and great vessels. In older patient it is atrophied and replaced by fatty tissue.

64. FOURTH PHARYNGEAL POUCH Epithelium of dorsal region forms superior parathyroid gland . Epithelium of ventral surface forms ultimobranchial body. When the parathyroid gland loses contact with wall of pharynx, it attaches itself to dorsal surface of the caudally migrating thyroid as superior thyroid gland.

65. ULTIMOBRANCHIAL BODY Later incorporated in thyroid gland. Cells of ultimobranchial body give rise to parafollicular or C-cells. C cells secrete calcitonin it regulates Ca level in blood.

66. BRANCHIAL CLEFT or GROOVES These grooves separate the pharyngeal arches externally. Out of four pairs, only first pair persists as the external acoustic meatus . Active growth of the 2 nd arch mesoderm overlaps 3 rd and 4 th arches.

67. Molecular regulation Neural crest cells arise from the neuroepithelial cells adjacent to the surface ectoderm all along the edges of neural folds. In the hind brain the crest cells originate in a specific pattern from segments called rhombomeres . There are 8 segments in the hind brain R1-R8.

68. Neural crest cells from specific segments migrate to populate specific pharyngeal arches. R1&R2 cells migrate to first arch. R4 cells to second arch. R6 &R7 fourth and sixth arch. Neural crest cells that populate the pharyngeal arch form the skeletal components.

69. It is divided by three streams:

70. Pouches are formed by migrating endoderm cells laterally, this migration is stimulated by fibroblast growth factors.(FGF’s) As pouches form they express a very characteristic pattern of genes. - BMP7 -posterior ectoderm of each pouch .

71. FGF8 -lies in the anterior ectoderm. PAX1- dorsal most endoderm of each pouch. SHH – posterior endoderm of second and third arch. Function of these genes is regulate differentiation and patterning of pharyngeal arch mesenchyme into specific skeletal structures.

72. Previously it was thought that neural crest cells regulated the patterning of these skeletal elements but its clear that this process is controlled by pharyngeal pouch endoderm. Formation of pharyngeal pouches prior to neural crest cells.

73. In this process there is epithelial mesenchymal interaction. The response of the mesenchyme to endodermal signals is dependent on the transcription factors expressed in that mesenchyme . Transcription factors include HOX gene &other caused by neural crest cells into arch.

74. First arch is HOX negative but does express OTX2. OTX2: orthodenticle homeobox 2 - Subfamily of HOX gene. - Containing transcription factor that is expressed in midbrain. Second arch by HOXA2.

75. Third arch to sixth arch express by the members of paralogus group of HOX genes.ie HOXA3,HOXB3,HOXD3.

76. ANOMALIES OF DEVELOPMENT BRANCHIAL POUCHES AND CLEFT Branchial anomalies are composed of heterogeneous group of congenital malformations. That arise from incomplete obliteration of pharyngeal cleft and pouches. Second most common congenital head and neck lesion found in children .

77. Branchial arch anomalies may present as cysts, sinus, fistula or cartilaginous remnants. Sinus: Is a blind ending tract and in context of branchial arch anomaly may connect either with skin ( branchial cleft sinus) or with pharynx ( branchial pouch sinus).

78. Fistula: Communication between two epithelial surface with regard to branchial arch anomalies, requires communication between a persist pouch and cleft. If there is no communication occurs with inner mucosa or outer skin, then trapped branchial arch remnant forms cyst.

79. Second brachial cleft lesion accounts for 95%of common. First branchial cleft lesion comprises only 1%. Third and fourth branchial cleft lesion are quite rare.

80. FIRST CLEFT ANOMALIES ANATOMY Course close to parotid gland particularly the superficial lobe. The tract may pass above, between or below the branches of facial nerve.

81. Anomaly is classified by Work in 1972 Classification Type I Type II Type I: Duplication of membraneous external auditory canal. Contains ectodermal elements only. The cyst is located within the parotid gland.

82. Type II: Lesions are composed of ectoderm and mesoderm therefore may contain cartilage. Pass medial to the nerve and may present as preauricular , infraauricular , or post auricular swellings or cysts inferior to angle of mandible.

83. Clinical features They commonly found in girls. Cleft remnants appears as a cyst, sinus, or fistula. Between the external auditory canal and submandibular . Symptoms: a)Cervical symptoms. b)Parotid symptoms.

84. c) Auricular symptoms. Cervical symptoms: Drainage from pit like depression at the angle of the mandible. If the tract becomes infected it can cause submandibular adenitis.

85. Parotid symptoms : Present as a mass and noticed due to rapid increase in size caused by inflammation. Auricular symptoms: Otorrhea with a mucous or purulent discharge from the ear.

86. Histopathology Both respiratory and squamous epithelium alone or in combination may line branchial lesion. Cyst are more lined by squamous epithelium. Sinus and fistulae are more likely to contain ciliated columnar epithelium. Cholestrol crystals. Squamous cell carcinoma has been reported.

87. Treatment Likely to require dissection of the facial nerve and superficial parotidectomy . Additionally it is necessary to excise the involved skin and cartilage of external auditory canal. Acute infections should be treated with antibiotics and needle aspiration .

88. SECOND CLEFT ANOMALIES Anatomy Anomalies pass close to glossopharyngeal and hypoglossal nerves and then enter into pharynx at the level of tonsillar fossa . Present within the submandibular space but they can occur anywhere along the course of second branchial arch tract which extends from the skin overlying supraclavicular fossa between ICA &ECA.

89. Classification by Bailey in 1929 Type I Type II Type III Type IV

90. Type I

91. Type II

92. Type III

93. Type IV

94. Clinical features A fistula or cyst found in the lower, anterior lateral region of neck. CYST FISTULA 3 -4 th decade. Infancy or childhood. Non tender mass in neck. Chronic drainage from an opening along the anterior border of SCM in the lower third of neck. Can lead to respiratory distress, torticollis,and dysphagia .

95. Treatment Complete surgical excision by a transverse cervical incision within the natural skin fold.

96. THIRD CLEFT ANOMALIES Anatomy There are found along the anterior border of SCM and pass deep to the internal carotid artery and glossopharyngeal nerve and superficial to superior laryngeal nerve, opening internally in base of pyriform fossa .

97. Clinical features Are uncommon. Most seen on the left side of the neck. Cyst have been reported to cause hypoglossal nerve palsy when they become infected.

98. Treatment Complete surgical excision by a transverse cervical incision. Chemo –cauterization.

99. FOURTH CLEFT ANOMALIES Anatomy The course of the tract depends on which side it occurs, On right side, lesions loop around the subclavian Pass deep to internal carotid artery

100. Ascending to the level of hypoglossal nerve Descends along the anterior border of SCM Enters the pharynx at the level of pyriform apex or cervical esophagus.

101. On left side: loops over the anterior aortic arch, medial to ligamentum arteriousus . The tract descends into the mediasternum

102. Clinical features Extremely rare. Present as cyst in the lateral lower third of the neck. Present with infection and manifest with suppurative thyroiditis .

103. Treatment Ipsilateral hemithyroidectomy . Partial resection of thyroid cartilage .

104. References Sperber -Craniofacial development Inderbir singh –Human embryology 8 th edition. T.W Sadler - Langmans medical embryology 12 th edition. Waldhausen J H T.branchial cleft and arch anomalies.seminars in pediatric surgery 2006;15:64-69 Grevellec A,Tucker A S.Pharygeal pouches and .seminars in cell and development biology.2010;(21):325-332.

105. Trainor P A and Krumlauf R. Hox genes, neural crest cells and branchial arch patterning.Current opinion in cell biology2001;13:698-705 Poswillo D. The pathogenesis of first and second branchial arch syndrome.Oral surgery 1973;35(3): 302-705 Graham A. Development and evolution of pharyngeal arches. J. Anat 2001;199:133-141 Adams A, Mankad K, Childs L. Branchial cleft anomalies ;a pictorial review of embryological development and spectrum of imaging findings.Insights Imaging 2016;7(1): 69- 76