Cartilages and muscles of larynx and pharynx develop from?
Ans. A. 4th and 6th branchial arch.Clefts = ectoderm Arches = mesoderm Pouches = endoderm. The 4th arch gives rise to: most pharyngeal constrictors; cricothyroid, levator veil palatini and 6th arch gives rise to ail intrinsic muscles of larynx except cricothyroid. Cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform also develop from 4th amd 5th arches.Branchial arch derivativesPharyngeal ArchArch ArteryCranial NerveSkeletal elementsMuscles1Terminal Branch of maxillary arteryMaxillary and mandibular division of trigeminal (V)Derived from arch cartilages (originating from neural crest):- From maxillary cartilages: Alispenoid, incus- From mandibular: Meckel's cartilage, malleusUpper portion of external ear (auricle) is derived from dorsal aspect of 1st pharyngeal arch.Derived by direct ossification from arch dermal mesenchyme-Maxilla, zygomatic, squamous portion of temporal bone, mandibleMuscles of mastication (temporalis, masseter, and pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini (originate from cranial somitomere 4)2Stapedius artery (embryologic) & cortiotympanic artery (adult)Facial nerve (VII)Stapes, styloid process, stylohyoid ligament, lesser horns and upper rim of hyoid (derived from the second arch/ Ritcher's cartilage; originate from neural crest).Lower portion of external ear (auricle) is derived from 2nd pharyngeal arch.Muscles of facial expression (orbicularis oculi, orbicularis oris, auricularis, piatysma, fronto-ooccipitalis, buccinator), posterior belly of digastric, stylohyoid, stapedius (originate from cranial somitomere 6)3Common carotid artery, most of internal carotidGlossophary- ngeal (IX)Lower rim and greater horn of hyoid (derived from the third arch cartilage; originate from neural crest ceils)Sytlopharyngeus (originate from cranial somitomere 7)4Left: Arch of aorta; Right: Right subclavian artery; Original sprouts of pulmonary art.Superior laryngeal branch of vagus (X)Laryngeal cartilages (Derived from the 4th arch cartilage, originate from lateral plate mesoderm)Constrictors of pharynx cricothyroid, levator veli palatine (originate from occipital somites 2-4)5Ductus arteriosus; roots of definitive pulmonary arteriesRecurrent laryngeal branch of vagus (X)Laryngeal cartilages (derived from the Se- arch cartilage; originate from lateral plate mesoderm)Intrinsic muscles of larynx (originate from occipital somites 1 and 2) Derivates of pharyngeal pouches:First pouchAuditory tube, which comes in contact with epithelial line of first pharyngeal cleft, where future external acoustic meatus will form.Distal portion will form tympanic cavity (lining will become eardrum).Proximal portion will become auditory tube.Second pouchForms buds that penetrate surrounding mesenchyme, which together form the palatine tonsilsThird pouchForms thymus and inferior parathyroid glandsFourth pouchForms superior parathyroid glandsFifth pouchForms utlimobranchial body Derivatives of pharyngeal clefts/grooves:Initially, four clefts exist; however, only one gives rise to a definite structure in adults.1st pharyngeal cleftPenetrates underlying mesenchyme and forms EAM. The bottom of EAM forms lateral aspect of tympanic cavity.2nd pharyngeal cleftUndergoes active proliferation and overlaps remaining clefts. It merges with ectoderm of lower neck such that the remaining clefts lose contact with outside. Temporarily, the clefts form an ectodermally lined cavity, the cervical sinus, but this disappears during development
4th and 6th branchial arch
4th and 3rd branchial arch
3rd and 2nd branchial arch
2nd and 4th branchial arch
Embryology