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

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