BRANCHIAL POUCH

Pharyngeal or branchial pouches form on the endodermal side between the branchial arches, and pharyngeal grooves (or clefts) form from the lateral ectodermal surface of the neck region to separate the arches. The pouches line up with the clefts, and these thin segments become gills in fish.

First pouch

• This is the only pouch in which the endoderm and ectoderm remain close together, as the tympanic membrane. There is minimal mesoderm in the tympanic membrane.
• The endoderm becomes the auditory tube, middle ear and mastoid antrum.
• The ectoderm becomes the external acoustic meatus

Second pouch

• Contributes to the middle ear, tonsils, supplied by the glossopharyngeal nerve.

Third pouch

• Derivatives include the inferior parathyroid glands and thymus

Fourth pouch

• Derivatives include the superior parathyroid gland and parafollicular C-Cells of the thyroid gland.

Fifth pouch

• Rudimentary structure, becomes part of the fourth pouch.

See also

• branchial arch
• DiGeorge syndrome

External links

• Outline at howard.edu (scroll down to "III. THE PHARYNGEAL POUCHES")
• Diagram at embryology.ch (Item #1 at Fig. 14
• Diagram at temple.edu