Which of the following structure is NOT present at bih?
Mastoid tip is absent at the time of bih but mastoid antrum is present. Postnatally, mastoid air cells develop leading to formation of mastoid process (by about 2 years ago). At bih, only the maxillary and ethmoidal sinuses are present and are large enough to be clinically significant. Malleus and incus are derived from Meckel's cailage of the first branchial (pharyngeal) arch before bih. .
Ethmoid sinus
Mastoid tip
Incus
Malleus