A. Hyoid arch.
B. Tuberculum impar.
C. Mandibular arch.
D. Hypobranchial eminence.
Ans:D. Hypobranchial Eminence.
The structure marked as number “5” (Red arrow) in the picture above represents the Hypobranchial Eminence.
The hypopharyngeal eminence or hypobranchial eminence is a midline swelling of the third and fourth pharyngeal arches, in the development of the tongue.
It appears in the fifth and sixth weeks of embryogenesis.
The hypopharyngeal eminence forms mostly from the endoderm of the third pharyngeal arch and only partially from the fourth pharyngeal arch.
It quickly grows to cover the copula formed earlier from the second pharyngeal arch, and will form the posterior one third of the tongue.