Although 3rd pharyngeal pouch
was not visible in this section, the location of thymus and para thyroid primordia approximated to that of 3rd pharyngeal pouch
The chorda tympani nerve comes off rostrally, courses ventrally to the first pharyngeal pouch
, and enters the mandibular arch.
The pharyngeal gut extending from the buccopharyngeal membrane to the tracheobronchial diverticulum consists of pharyngeal (branchial) archs, pharyngeal clefts, and pharyngeal pouches
. Five pairs of pharyngeal pouches
lined by the endoderm give rise to the middle ear cavity, auditory tube, tympanic membrane (first one), palatine tonsils (second one), thymus and inferior parathyroid glands (third one), superior parathyroid glands (fourth one) and finally, parafollicular cells of the thyroid gland (fifth one).
It has recently been postulated that pathophysiology of the pharyngeal pouches
involves altered compliance of the cricopharyngeus muscle, detected as impaired pharyngeal opening or raised intrabolus pressure.
Thyroid gland is developed via intussusception from the endoderm of the primitive pharynx between the 1st and the 2nd pharyngeal pouches
. This canal reaches the state of intussusception on days 16-17 of gestation.
(1-4) The arches are embryologically separated by 4 pharyngeal (or branchial) clefts laterally and 4 pharyngeal pouches
Gland arises due to proliferation of endodermal epithelial cells on the medial surface of developing pharyngeal gut between first and second pharyngeal pouches
Laryngeal and pharyngeal pouches
. Surgical approach and the use of cinefluorographic and other radiologic techniques as diagnostic aids.
(1) The development of many structures in the head and neck is immediately related to either the branchial arches or the pharyngeal pouches
. (2) The makeup of these embryologic structures is transient, as they undergo remodeling to the point that their original forms are essentially unrecognizable in adults.
Older theories hold that they are congenital abnormalities caused by an incomplete obliteration of pharyngeal pouches
. (2-4) Proponents of more recent theories regard them as epithelial inclusions within cervical lymph nodes that can trigger cystic degeneration.