Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
The mother of a 7-year-old boy expresses concern to her pediatrician that her son has developed an irritated swelling on the side of his neck. Palpation reveals a small, mucus-secreting cyst along the anterior border of the sternocleidomastoid muscle. This branchial sinus, or external cervical fistula, is the result of incomplete obliteration of which of the following developmental structures?
A. First pharyngeal arch
B. First pharyngeal cleft
C. First pharyngeal pouch
D. Second pharyngeal arch
E. Second pharyngeal cleft
F. Second pharyngeal pouch
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
E is correct answer
The correct answer is E. In normal development of the neck, the second pharyngeal cleft grows inferiorly to fuse with the cardiac ridge, thereby obliterating clefts 2-4. The cervical sinus formed by the fusion of these tissue masses is normally a transient structure, but may persist as a cyst, external fistula, or internal fistula.
The first pharyngeal arch (choice A) gives rise to various bony, muscular and ligamentous structures: the malleus and incus; the muscles of mastication, plus the tensor tympani, tensor veli palatini, mylohyoid and anterior digastric; the sphenomandibular ligament and anterior malleolar ligament.
clefts are outside... pouches inside... and arches in the middle...!!!!!
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
The first pharyngeal cleft (choice B) is retained as the external auditory meatus and canal.
The first pharyngeal pouch (choice C) gives rise to the tympanic cavity and auditory tube.
The second pharyngeal arch (choice D), like the first, gives rise to bones, muscles and ligaments: the stapes and lesser horn and upper part of the body of the hyoid bone; the muscles of facial expression, plus the stapedius, stylohyoid and posterior digastric; the stylohyoid ligament.
The second pharyngeal pouch (choice F) becomes the tonsillar bed.
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
thanks raji.I wish proteus learn a lesson from u.
