DEVELOPMENT OF TONGUE THYROID GLAND, FACE AND PALATE By Dr Samina Anjum

PHARYNGEAL ARCHES

Taste Buds Anterior 2/3 tongue - Cranial nerve VII Circumvallate papillae - Cranial nerve IX 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 Treacher Collins Syndrome 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 Labial Components (Philtrum) Maxilla Component (Alveolus + 4 Incisors) 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

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