Pharyngeal Pouches

 

I - IV -        pharyngeal arches

1 -  4 inside - pharyngeal pouches

1 - 4 outside - pharyngeal grooves

a - tuberculum laterale

b - tuberculum impar

c - foramen ceccum

d - ductus thyreoglossus

 e -sinus cervicalis

 

From the 1st pouch - epithelial lining of auditory tube & middle ear cavity

from the 2nd pouch - epithelial lining of crypts of palatine tonsil

from the 3rd pouch - Inferior parathyroid gland

     -  Thymus

from the 4th pouch - Superior parathyroid gland

                          -  ultimobranchial body

 

DiGeorge sequence is when pharyngeal pouches 3 & 4 do not differentiate into what they have to (parathyroid gland & thymus).

 

Thyroid gland develops from the midline of endoderm of the oropharynx & migrates inferiorly along the path of thyroglossal duct.