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Periotic bone: the petrous and mastoid parts; Two parts of the hyoid arch: the styloid process. In the dog these small bones are called tympanohyal (upper) and stylohyal (lower). In evolutionary terms, the temporal bone is derived from the fusion of many bones that are often separate in non-human mammals:
The periotic bone is the single bone that surrounds the inner ear of birds [1] and mammals. It is formed from the fusion of the prootic , epiotic , and opisthotic bones, and in Cetacea forms a complex with the tympanic bone .
In the auditory region (including the temporal bones), the periotic bone of the inner ear is extensive, the internal auditory meatus and facial canal openings of the temporal bone being visible in the lower triangular area of the periotic bone. The tympanic part of the temporal bone is connected partially to the squamosal bone, remains separate ...
Each gland lies behind the mandibular ramus and in front of the mastoid process of the temporal bone. The gland can be felt on either side, by feeling in front of each ear, along the cheek, and below the angle of the mandible. [4] The parotid duct, a long excretory duct, emerges from the front of each gland, superficial to the masseter muscle.
The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones.Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three angles, and houses in its interior the components of the inner ear.
The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear in the temporal bone. It consists of three parts: the vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the substance of the bone, and lined by periosteum.
Anteriorly, the posterior cranial fossa is bounded by the dorsum sellae, posterior aspect of the body of sphenoid bone, and the basilar part of occipital bone/clivus. [2] Laterally, it is bounded by the petrous parts and mastoid parts of the temporal bones, and the lateral parts of occipital bone. [2]
Within the temporal bone, a groove projects outward the subarcuate fossa. The internal acoustic meatus canal of the ear has a deep, oval shape with fixed boundaries from clear edges, containing two roughly equal in size foramina. The petrosal bone in context of the front area near the internal acoustic meatus has a reduced area extension. [38]