Stapes

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Description:

The stapes is the smallest of the three ear ossicles. This bone, as its name suggests, forms a remarkable resemblance to a stirrup. It has a small rounded head with a flattened articular facet positioned on a pillar-like neck. From the base of the neck two diverging processes or crura project to a large oval base, or footplate. The bone has an interesting evolutionary history. It arises from the second, or hyoid, gill bar. In fishes this bone, the hyomandibula formed the primitive jaw suspension. It became, in the first tetrapod vertebrates, the columella of the middle ear anatomy, serving as the single element between the tympanic membrane and oval window. In mammals it becomes the medial most ear ossicle and transmits forces from the incus to the oval window of the inner ear.