Petrous portion

Petrous portion

The petrous portion (also known as the petrous part of the temporal bone) is a pyramid-shaped, dense part of the temporal bone that houses the structures of the inner ear. It is one of the most complex and vital areas of the human skull, playing a crucial role in hearing and balance.

Anatomy

The petrous portion is located at the base of the skull, between the sphenoid bone and the occipital bone. It is divided into three main parts: the anterior surface, the posterior surface, and the inferior surface.

Anterior Surface

The anterior surface of the petrous portion faces the middle cranial fossa. It contains the trigeminal impression, which is the site where the trigeminal ganglion is located. This surface also features the arcuate eminence, a rounded elevation that indicates the position of the superior semicircular canal of the inner ear.

Posterior Surface

The posterior surface of the petrous portion faces the posterior cranial fossa. It contains the internal acoustic meatus, a canal that transmits the facial nerve (CN VII) and the vestibulocochlear nerve (CN VIII). This surface also features the subarcuate fossa, a small depression that houses the flocculus of the cerebellum.

Inferior Surface

The inferior surface of the petrous portion is rough and irregular. It contains the jugular foramen, which transmits the internal jugular vein and several cranial nerves, including the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), and the accessory nerve (CN XI). This surface also features the carotid canal, which transmits the internal carotid artery.

Function

The petrous portion of the temporal bone is essential for protecting the delicate structures of the inner ear, including the cochlea, the vestibule, and the semicircular canals. These structures are responsible for converting sound waves into nerve impulses and for maintaining balance and spatial orientation.

Clinical Significance

Due to its dense and complex structure, the petrous portion is often involved in various medical conditions, including temporal bone fractures, cholesteatoma, and acoustic neuroma. Imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) are commonly used to diagnose conditions affecting the petrous portion.

Related Pages

• Temporal bone
• Inner ear
• Cranial nerves
• Middle cranial fossa
• Posterior cranial fossa
• Internal acoustic meatus
• Jugular foramen
• Carotid canal