Temporal bone

Os temporale

A paired bone at the side and base of the skull that houses the ear and forms the upper half of the jaw joint.

At a glance

English: Temporal bone
Latin (TA2): Os temporale
System: Bone
Region: Head
Side: Paired, left and right
Muscles on it: Temporalis

About the temporal bone

Each temporal bone makes up part of the side wall and floor of the cranium, beneath the temple and outside the temporal lobe of the brain. It encloses the middle and inner ear, carries the socket for the lower jaw and is crossed by several important nerves and vessels. Anatomists divide it into squamous, petrous, tympanic and mastoid portions, with the slender styloid process jutting from its underside.

The squamous part is a thin, flat plate rising above the ear and forming part of the temporal fossa. From its lower edge the zygomatic process arches forward to the zygomatic bone, making the back half of the cheek arch, and under its root lies the mandibular fossa where the head of the mandible sits. Behind and below is the mastoid part, whose rounded mastoid process can be felt behind the ear; it is filled with air cells and anchors sternocleidomastoid and other neck muscles, with a notch on its inner side for the digastric. The small tympanic part curves below the squama, in front of the mastoid, and forms most of the bony ear canal. The styloid process points down and forward between the parotid gland and the internal jugular vein.

The petrous part is a dense pyramid wedged into the skull base, with the sphenoid in front and the occipital bone behind, its apex aimed forward and inward. Its front face looks into the middle cranial fossa and shows the arcuate eminence and the thin tegmen tympani over the middle ear; its back face looks into the posterior fossa and holds the internal acoustic meatus for the facial and vestibulocochlear nerves. Inside lie the cochlea, the vestibule and the three semicircular canals of the bony labyrinth, and the carotid canal carries the internal carotid artery through it. The bone meets the parietal, sphenoid, zygomatic and occipital bones at named sutures.

Clinically, a fracture through the petrous part can cause bleeding or clear fluid from the ear, hearing loss and facial weakness. The mastoid air cells open into the middle ear, so an ear infection can spread into them as mastoiditis, or upward through the tegmen towards the brain. An overlong styloid process, or a calcified stylohyoid ligament, can cause throat and neck pain in Eagle syndrome.

Function and supply

Function: Protects the organs of hearing and balance, provides the upper surface of the jaw joint, and anchors temporalis, masseter (through the zygomatic arch) and several neck muscles.
Nerve supply: Not supplied as a muscle is; the facial and vestibulocochlear nerves run within it, the auriculotemporal nerve supplies the skin over the squama, and meningeal branches of the trigeminal nerve supply the dura on its inner surface.
Blood supply: The middle meningeal and superficial temporal arteries supply the squama; the mastoid and petrous parts receive branches of the posterior auricular, stylomastoid, ascending pharyngeal and middle meningeal arteries, and the inner ear is fed by the labyrinthine artery.

Parts of the temporal bone

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Anterior surface of petrous partFacies anterior partis petrosaeThe upper front face of the petrous pyramid, forming the back of the middle cranial fossa. It carries the arcuate eminence and tegmen tympani, and the trigeminal ganglion rests in a shallow dip near its apex.
Apex of petrous partApex partis petrosaeThe blunt front tip of the pyramid, pointing forward and towards the midline. It lies between the sphenoid and the basilar occipital beside the foramen lacerum, where the internal carotid artery leaves the carotid canal.
Arcuate eminenceEminentia arcuataA rounded bulge on the front face of the petrous part. It overlies the anterior semicircular canal and guides surgeons approaching the inner ear from above.
Lateral bony ampullaAmpulla ossea lateralisThe swelling at the front end of the lateral semicircular canal, where it opens into the vestibule. It houses the sensory crest that responds to turning of the head in the horizontal plane.
Mastoid notchIncisura mastoideaA deep groove on the inner side of the mastoid process. The posterior belly of digastric arises from it.
Mastoid processProcessus mastoideusThe rounded projection behind the ear, filled with air cells that open into the middle ear. Sternocleidomastoid, splenius capitis and longissimus capitis attach to it, and it grows as these muscles develop after birth.
Occipital margin of temporal boneMargo occipitalis ossis temporalisThe back edge of the mastoid part. It meets the occipital bone at the occipitomastoid suture.
Petrous part of temporal bonePars petrosa ossis temporalisThe dense pyramid of bone in the skull base, lying between the occipital and sphenoid bones. It holds the cochlea, the vestibule and the semicircular canals and is the hardest bone of the skull.
Posterior bony ampullaAmpulla ossea posteriorThe swelling at the lower end of the posterior semicircular canal, opening into the vestibule. Its sensory crest is the one most often disturbed by loose crystals in benign positional vertigo.
Posterior surface of petrous partFacies posterior partis petrosaeThe back face of the pyramid, looking into the posterior cranial fossa towards the cerebellum. It carries the internal acoustic meatus for the facial and vestibulocochlear nerves.
Simple bony limbCrus osseum simplexThe unswollen end of the lateral semicircular canal, which opens into the vestibule by itself. The other two canals instead share their unswollen ends in the common limb.
Squamous part of temporal bonePars squamosa ossis temporalisThe thin, flat upper plate forming the side of the skull under the temple. Temporalis arises from its outer face, its zygomatic process forms the back of the cheek arch, and the mandibular fossa lies under that root.
Styloid process of temporal boneProcessus styloideus ossis temporalisA slender spike projecting down and forward from the underside of the bone, below the ear. Styloglossus, stylohyoid and stylopharyngeus arise from it, and the stylohyoid ligament runs from its tip.
Tegmen tympaniA thin plate on the front face of the petrous part that roofs the middle ear and mastoid antrum. Only this thin bone separates the middle ear from the temporal lobe, so infection can spread upward through it.
Tympanic part of temporal bonePars tympanica ossis temporalisA curved plate below the squama and ahead of the mastoid process. It forms the floor and the front and back walls of the bony external ear canal.

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At a glance

About the temporal bone

Function and supply

Related structures

See the temporal bone where it really sits, with every layer of the body around it.