Development of the tongue and thyroid
First pharyngeal arch
Third Branchial arch
Second pharyngeal arch
4th arch
proliferation of mesoderm in floor of pharynx
Median tongue bud (tuberculum impar)
Distal tongue buds (lateral lingual swellings)
rapidly over grow tuberculum impair
anterior 2/3 of tongue
mesoderm
hypobranchial/hypopharyngeal eminence
mesoderm
copula
hypobranchial eminence covers copula
posterior 1/3 of tongue
contributes to
forms root of tongue and epiglottis
whole tongue
dorsal endoderm of tongue
Thyroid diverticulum
descends ventral/anterior to hyoid and larynx
Thyroglossal duct is formed opening into foramen caecum
Thyroid gland over upper trachea
Thyroglossal duct disintegrates
foramen caecum remains as a small pit on dorsal tongue
in some individuals an inferior remnant remains
forms pyramidal lob connecting isthmus of thyroid to hyoid bone by fibrous tissue or muscle