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Stapes

Other Terms: Stirrup, Stapès

Type

irregular

Description

This is the smallest of the three ear ossicles. This bone, as its name suggests, forms a remarkable resemblance to a stirrup. It has a round head with a flattened articular facet positioned on a pillar-like neck. From the base of the neck two diverging processes or crura project into an oval base. 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.

Etymology

Stapes is a Later Latin term meaning stirrup. It arises from the Early Latin words stare meaning to stand and pes meaning foot. It was first named by the Italian anatomist Ingrassias in 1546.

Articulations

The stapes articulates with one other bone: the incus. The head of the stapes has a flat, round articular facet that forms a synovial joint with the lenticular process of the incus.

Ossification

This bone ossifies endochondrally in the cartilaginous anlage of the hyoid arch. It forms from a single center that appears during the fourth month in the base of the bone. It is usually completely ossified by birth.

French

Stapès

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