Pharyngeal pouches

Outline

Pharyngeal pouch evolution

Slide 4

 Fate of pharyngeal grooves 2-4

Fate of 1^st pharyngeal groove and pouch

First groove     external auditory meatus

Slide 8

First pouch      pharyngotympanic tube

External ear receives contributions from arches 1 and 2

External ear development by merging of 6 auricular hillocks

External ear and tongue development require merging: the elimination of a groove between facial processes by differential growth.

Endodermal swellings on arches  1-4 contribute to the tongue

Merging of lingual swellings

Thyroid gland development. Thyroglossal duct

Descent of developing thyroid. Thyroglossal tract is no longer intact, allowing gland to move.

Adult thyroid gland

Thyroid gland

Slide 19

Pharyngeal pouch at 4 weeks

Slide 21

Derivatives of dorsal and ventral parts of pharyngeal pouches

Second pharyngeal pouch,ventral: development of palatine tonsil

Palatine tonsil

Palatine tonsil: epithelium of  tonsillar crypt

Third pharyngeal pouch, ventral:
development of thymus

Thymus development

Slide 28

Thymus histogenesis

Thymus

Third pharyngeal pouch, dorsal: inferior parathyroid gland

Fourth pharyngeal pouch, dorsal: superior parathyroid gland

Parathyroid gland

Fourth pharyngeal pouch, ventral: ultimobranchial bodies