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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. [8] Two parts of the hyoid arch: the styloid process.
The ectotympanic, or tympanicum, is a bony structure found in all mammals, located on the tympanic part of the temporal bone, which holds the tympanic membrane (eardrum) in place. In catarrhine primates (including humans), it takes a tube-shape.
The inner ear sits within the temporal bone in a complex cavity called the bony labyrinth. A central area known as the vestibule contains two small fluid-filled recesses, called the utricle and saccule. These connect to the semicircular canals and the cochlea. There are three semicircular canals angled at right angles to each other which are ...
In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts: [2] The cochlea, dedicated to hearing; converting sound pressure patterns from the outer ear into electrochemical impulses which are passed on to the brain via the auditory nerve.
In all extant and extinct primates, including humans, the auditory bulla is formed by the petrosal bone (the petrous part of the temporal bone). This is a diagnostic trait that can be used to distinguish primates, including anthropoids, tarsiers, lemurs, and lorises, from all other mammals. [3]
These extended margins of thinned bone are called supratemporal fossae. Synapsids, including mammals, have one temporal fenestra, which is ventrally bordered by a zygomatic arch composed of the jugal and squamosal bones. This single temporal fenestra is homologous to the infratemporal fenestra, as displayed most clearly by early synapsids. [2]
The entotympanic is a bone found in the ear region of many placental mammals.When present it forms the medioventral part of the auditory bulla; it is a neomorphic element derived from the tubal cartilage and the sheath of the tympanohyal.
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles.