The petrous portion of the temporal bone or pyramid is pyramidal and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents for examination a base, an apex, three surfaces, and three angles, and contains, in its interior, the essential parts of the organ of hearing. The petrous portion is among the most basal elements of the skull and forms part of the endocranium.[WP,unvetted]. [ ]

Synonyms: petromastoid part of temporal bone temporal bone petrous part pars petrosa ossis temporalis pars petrosa (os temporale)

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Term information



depicted by

external definition

The petrosal bone arises from the two otic bones on the lateral wall of the chondrocranium and encases the inner ear of mammals. [Bemis_WE, Functional_Anatomy_of_the_Vertebrates:_An_Evolutionary_Perspective, Grande_L, Third_Edition_(2001)_Orlando_Fla.:_Harcourt_College_Publishers, Walker_WF, p.258, see_Liem_KF][VHOG]

has related synonym

petrous bone

petrosal bone



taxon notes

derivative of prootic and opisthotic