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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 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.
Other ossicles include spines, tubercles, small scales and vertebrae. The large central vertebrae in each arm segment provides the articulating element that joins it to the next. [7] Crinoid fossils from the Jurassic showing ossicles. Several types of small ossicles are found in the body wall of sea cucumbers. Baskets are cup-shaped and usually ...
The evolutionary process leading to a three-ossicle middle ear was thus an "accidental" byproduct of the simultaneous evolution of the new, secondary jaw joint. In many mammals, the middle ear also becomes protected within a cavity, the auditory bulla, not found in other vertebrates. A bulla evolved late in time and independently numerous times ...
The ossicles are the malleus (hammer), incus (anvil), and the stapes (stirrup). The stapes is the smallest named bone in the body. The middle ear also connects to the upper throat at the nasopharynx via the pharyngeal opening of the Eustachian tube. [3] [11] The three ossicles transmit sound from the outer ear to the inner ear.
The stapes is the third bone of the three ossicles in the middle ear and the smallest in the human body. It measures roughly 2 to 3 mm , greater along the head-base span. [ 1 ] It rests on the oval window , to which it is connected by an annular ligament and articulates with the incus , or anvil through the incudostapedial joint . [ 2 ]
The middle ear consists of a space spanned by three small bones called the ossicles. The three ossicles are the malleus, incus, and stapes, which are Latin names that roughly translate to hammer, anvil, and stirrup. The malleus is attached to the tympanic membrane and articulates with the incus.
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.