A manual of anatomy . For detailssee page 350. 54 OSTEOLOGY The petromastoid portion (pars petrosa et pars mastoidia) is the most massive division and is pyramidal in form. The petrous part{pyramis) is a long, three-sided pyramid with an apex, a base, threesurfaces and three margins. The apex is near the middle line of thebase of the cranium at the body of the sphenoid. The base is fusedwith the squamous and tympanic portions. The anterior surfaceforms a part of the floor of the middle cranial fossa and is smooth butirregular; it may show impressions of the gyri of the temporal lobe ofthe cere
A manual of anatomy . For detailssee page 350. 54 OSTEOLOGY The petromastoid portion (pars petrosa et pars mastoidia) is the most massive division and is pyramidal in form. The petrous part{pyramis) is a long, three-sided pyramid with an apex, a base, threesurfaces and three margins. The apex is near the middle line of thebase of the cranium at the body of the sphenoid. The base is fusedwith the squamous and tympanic portions. The anterior surfaceforms a part of the floor of the middle cranial fossa and is smooth butirregular; it may show impressions of the gyri of the temporal lobe ofthe cerebrum. Near the apex is the impressio trigemina whichlodges the semilunar ganglion of the trigeminal nerve. On thissurface are seen the eminentia arcuata, made by the superior semi-circular canal; near this is the slit-like hiatus canalis facialis, for thefacial nerve; a little lateral to the hiatus may be a small opening, the Parietal border Cerebral surface Sulcus arleriosus -fSphenoidal border Petrous port/on (apex). Arcuate eminence Parietal nolcliSuperior petrosal groove Subarcuate fossaInternal auditory meatus Inferior petrosal groove \ Styloid process , Mastoid foramenOccipital border Sigmoid grooveI Orijice of aguedactas vestibiilifugular notch Fig. 29.—The right temporal bone seen from the cerebral surface. McMurrich.) (Sobotta and apertura superior canalis tympani. The posterior surface forms partof the posterior cranial fossa and is concave, smooth but the following are seen: (i) Internal auditory meatus {meatusanditorius internus) a long, oval opening in the depths of which theopening of the canalis faciahs may often be noted. The meatustransmits the acoustic nerve and vessels. (2) The aqueduct of thevestibule {apertura externa aqueductus vestibuli) is in front of the pre-ceding; this lodges the saccus endolymphaticus. (3) The ridge ofthe posterior semicircular canal is above this. The inferior surfaceis very irregular and mostly rough. The most promine
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecthumananatomy, bookyea
