Temporal bone

Bone: Temporal bone
Position of temporal bone (shown in green)
Structure of temporal bone (left)
Latin	Os temporale
Gray's	subject #34 138
Articulations	Occipital, parietal, sphenoid, mandible and zygomatic

The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebrum.

The temporal bone supports that part of the face known as the temple and houses the structures of the organ of hearing. The lower seven cranial nerves and the major vessels to and from the brain traverse the temporal bone.

Parts

The temporal bone consists of five parts:

• Squama temporalis
• Mastoid portion
• Petrous portion (Petrosal ridge)
• Tympanic part
• Styloid process

Borders

Occipitomastoid suture. It separates occipital bone and mastoid portion of temporal bone.  Squamosal suture. It separates parietal bone and squama portion of temporal bone.  Sphenosquamosal suture. It separates sphenoid bone and squama portion of temporal bone.  Zygomaticotemporal suture. It separates zygomatic bone and zygomatic process of temporal bone.

Composition

The structure of the squama is like that of the other cranial bones: the mastoid portion is spongy, and the petrous portion dense and hard.

In other animals

In evolutionary terms, the temporal bone is derived from the fusion of many bones that are often separate in non-human mammals:

• The squamosal bone, which is homologous with the squama, and forms the side of the cranium in many bony fish and tetrapods. Primitively, it is a flattened plate-like bone, but in many animals it is narrower in form, for example, where it forms the boundary between the two temporal fenestrae of diapsid reptiles.
• The petrous and mastoid parts of the temporal bone, which derive from the periotic bone, formed from the fusion of a number of bones surrounding the ear of reptiles. The delicate structure of the middle ear, unique to mammals, is generally not protected in marsupials, but in placentals, it is usually enclosed within a bony sheath called the auditory bulla. In many mammals this is a separate tympanic bone derived from the angular bone of the reptilian lower jaw, and, in some cases, it has an additional entotympanic bone. The auditory bulla is homologous with the tympanic part of the temporal bone.
• Two parts of the hyoid arch: the styloid process. In the dog the styloid process is represented by a series of 4 articulating bones, from top down tympanohyal, stylohyal, epihyal, ceratohyal; the first two represent the styloid process, and the ceratohyal represents the anterior horns of the hyoid bone and articulates with the basihyal which represents the body of the hyoid bone.

Additional images

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  Position of temporal bone (green). Animation.

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  Shape of temporal bone (left).

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  Cranial bones.

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  left temporal bone. Prepared and articulate

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  The skull from the front.

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  Sphenoid bone visible center right.

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  Side view of the skull.

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  Left infratemporal fossa.

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  Sagittal section of skull.

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  Articulation of the mandible. Lateral aspect.

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  Base of the skull. Upper surface.

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  Temporal bone

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  Temporal bone

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  Sphenoid and temporal bones

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  Mandibular fossa

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  Zygomatic arch

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  Mastoid process

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  Tympanic cavity. Facial canal. Internal carotid artery.

See also

• Ossification of temporal bone
• Bone terminology
• Terms for anatomical location
• Temporal fenestrae
• Temporomandibular joint
• temporal muscle

References

This article incorporates text from a public domain edition of Gray's Anatomy.

External links

• Roche Lexicon - illustrated navigator, at Elsevier 34256.000-1