Pharyngeal pouch (endoderm)

First pharyngeal pouch- form tubotympanic recess 

1. Proximal part of tubotympanic recess: Auditory / Eustachian tube 

2. Distal part of tubotympanic recess: Tympanic / Middle ear cavity

3. Inner layer (Endoderm) of tympanic membrane 


Secound pharyngeal pouch- 

1. Palatine tonsil 

2. Tonsilar fossa 


Third pharyngeal pouch- 

1. Ventral region: Thymus

2. Dorsal region: Inferior parathyroid gland  


Fourt pharyngeal pouch- 

1. Ventral region: Ultimobranchial body 

2 Dorsal region: Superior parathyroid gland 


NOTE: The parathyroid glands (superior and inferior) are located on the posterior/dorsal side of the thyroid, so the parathyroid glands (superior and inferior) are derived from the dorsal region of the 4th and 3rd pharyngeal pouches.


Reference: 

1. Langman's medical embryology, 13th edition, P. No. 284-86 

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