Development of Thyroid Gland• It is developed from endodermal cells of floor of

pharynx (area of developing tongue).• It begins a diverticulum at dorsum of tongue

between tuberculum impar and hypobranchial eminence.

• Elongation of thyroid diverticulum to form thyro-glossal duct. It elongates downwards infront hyoid and thyroid cartilage where it ends by dividing into 2 parts.

• Ultimobranchial body gives parafollicular cells to thyroid gland. Dr. Sherif

Fahmy

Dr. Sherif Fahmy

Foramen cecum

Thyroglossal diverticulum

Developing anterior 2/3 of tongue

Dr. Sherif Fahmy

Thyroglossal duct

Thyroid gland

Developing anterior 2/3 of tongue

Dr. Sherif Fahmy

Foramen cecum

Degenerating thyro-glossal duct

Hyoid bone

Thyroid cartilage

Levator glandulae thyroidaePyramidal lobe Lobe of

thyroid gland

Fate of Thyro-glossal Duct• Upper end of the duct remains as foramen cecum

on dorsum of tongue.• The duct degenerates from foramen cecum and

hyoid bone.• The duct from the hyoid to divisions of the duct

form levator glandulae thyroidae and may be pyramidal lobe.

• Divisions of the duct form lobes of thyroid gland with isthmus inbetween.

• Ultimobranchial body forms parafollicular cells of the gland.

Congenital Anomalies • Thyroid agenesis: Failure of its formation.• Lingual thyroid: Failure of thyroid descend.• Aberrant thyroid (Retrosternal goiter): over-

descend of thyroid gland in the thorax.• Thyroglossal cyst: It is persistence of a part of

the thyroglossal duct.• Thyroglossal fistula: Thyroglossal duct opens

to skin.

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Dr. Sherif Fahmy