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DEVELOPMENT OF TONGUE THYROID GLAND, FACE AND PALATE Dr Samina Anjum PHARYNGEAL ARCHES • Taste Buds • Anterior 2/3 tongue - Cranial nerve VII • Posterior 1/3 tongue - Cranial nerve IX • Most posterior part & Epiglottis - Cranial nerve X TONGUE TIE Development of Thyroid • The thyroid gland is the first endocrine gland to develop in embryo. • It begins to form about 24 days after fertilization • It develops from a median endodermal thickening in the floor of a primordial pharynx • Thickening soon forms a small outpouching called thyroid primordium Cont…. • As the embryo and tongue grow, the developing thyroid gland descends in the neck, passing ventral to the developing hyoid bone and laryngeal cartilages • For a short time the thyroid gland is connected to the tongue by a narrow tube, the thyroglossal duct, disappears later Cont… • At first the thyroid primordium is hollow but it soon becomes solid and divides into right and left lobes. • The two lobes are connected by the isthmus of the thyroid gland. • Isthmus lies anterior to the developing second and third tracheal rings. Cont… • By seventh week it has reached its final site in the neck • The proximal opening of the thyroglossal duct persists as a small pit in the tongue, the foramen cecum • A pyramidal lobe extends upward from the isthmus in about 50% of people • The pyramidal lobe and the associated smooth muscle represent a persistent part of the distal end of the thyroglossal duct Thyroglossal Duct Cysts & Sinuses Following infection of a cyst, a perforation of the skin occurs forming a thyroglossal duct sinus Lingual Thyroid DEVELOPMENT OF FACE STOMODIUM: Is the depression between five elevations. Opposed to the primitive pharynx by buccopharyngeal membrane, which will break down later, then stomodeum communicates with the foregut. Craniofascial Defects • • • • Treacher Collin’s syndrome Robbin’s sequence Digeorge anomaly Goldenhar syndrome First Arch Syndrome Two Major types; both result in extensive facial abnormalites 1. Treacher Collins Syndrome 2. Pierre Robin Syndrome Treacher Collins Syndrome • Autosomal dominant trait/teratogens • Malar hypoplasia • Mandibular hypoplasia • Down slanting palpepebral fissures • Malformed external ears Pierre Robin Syndrome • Genetic or envoirmental factors • Mandibular hypoplasia • Micrognathia • Cleft palate Digeorge anomaly •Disturbance of cervical neural crest migration. •Absence of thymus and parathyroid glands •Immunological deficiency, Hypocalcaemia, Poor prognosis DEVELOPMENT OF PALATE Intermaxillary Segment Forms 1. Labial Components (Philtrum) 2. Maxilla Component (Alveolus + 4 Incisors) 3. Palatal Component (Triangular Primary Palate) Secondary Palate Congenital malformations 1) cleft lip: a. unilateral cleft lip: results from failure of the maxillary prominence to merge with medial nasal prominence on the affected side b. bilateral cleft lip : results from failure of the maxillary prominences to merge with the medial nasal prominence on both sides c. median cleft lip: results from failure of the medial nasal prominences to merge and form the intermaxillary segments 2) oblique facial cleft: results from failure of the maxillary prominence to fuse with the lateral nasal prominence