temporal bone

Bone: Temporal bone
Cranial bones
Facial bones.
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.

The temporal bone supports that part of the face known as the temple.

Parts

Each consists of four parts:

• Squama temporalis
• Mastoid portion
• Petrous portion
• Tympanic part

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.

Additional images

The skull from the front.	Sphenoid bone visible center right.	Side view of the skull.	Left infratemporal fossa.
Sagittal section of skull.	Articulation of the mandible. Lateral aspect.	Base of the skull. Upper surface.

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 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.^[1]

The petrous and mastoid parts of the temporal bone 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 includes a separate tympanic bone derived from the angular bone of the reptilian lower jaw, and, in some cases, an additional entotympanic bone. The auditory bulla is homologous with the tympanic part of the temporal bone.^[1]

• 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.

See also

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

External links

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

References

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.