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The middle ear contains three tiny bones known as the ossicles: malleus, incus, and stapes. The ossicles were given their Latin names for their distinctive shapes; they are also referred to as the hammer, anvil, and stirrup, respectively. The ossicles directly couple sound energy from the eardrum to the oval window of the cochlea.
The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. . Although the term "ossicle" literally means "tiny bone" (from Latin ossiculum) and may refer to any small bone throughout the body, it typically refers specifically to the malleus, incus and stapes ("hammer, anvil, and ...
The stapes (stirrup) ossicle bone of the middle ear transmits vibrations to the fenestra ovalis (oval window) on the outside of the cochlea, which vibrates the perilymph in the vestibular duct (upper chamber of the cochlea). The ossicles are essential for efficient coupling of sound waves into the cochlea, since the cochlea environment is a ...
In the auditory system, sound vibrations (mechanical energy) are transduced into electrical energy by hair cells in the inner ear. Sound vibrations from an object cause vibrations in air molecules, which in turn, vibrate the ear drum. The movement of the eardrum causes the bones of the middle ear (the ossicles) to vibrate.
The evolution of mammalian auditory ossicles was an evolutionary process that resulted in the formation of the mammalian middle ear, where the three middle ear bones or ossicles, namely the incus, malleus and stapes (a.k.a. "the anvil, hammer, and stirrup"), are a defining characteristic of mammals.
Information, or stimuli, in the form of light enters the retina, where it excites a special type of neuron called a photoreceptor cell. A local graded potential begins in the photoreceptor, where it excites the cell enough for the impulse to be passed along through a track of neurons to the central nervous system .
These are called the primary tentacles and were present in the common ancestor of echinoderms, but have been lost in all the other classes of the phylum, [11] and may be simple, branched or arborescent. They are known as the introvert and posterior to them there is an internal ring of large calcareous ossicles.
The ossicles may bear external projections in the form of spines, granules or warts and they are supported by a tough epidermis. Skeletal elements are sometimes deployed in specialized ways, such as the chewing organ called " Aristotle's lantern " in sea urchins, the supportive stalks of crinoids, and the structural "lime ring" of sea cucumbers.