The stapes is one of the three small bones called ossicles that are located in the middle ear. It plays an important role in how sound vibrations travel through the ear and are heard. It is found in human embryos very early in development and is also found in other species of animals. The function of this delicate bone can become compromised due to health issues and disease, but it can be repaired.
The stapes is the smallest as well as the lightest bone in the human body. It has a shape and appearance similar to a saddle with a hole in the middle. The top or head portion is called the capitulum, the sides are the anterior crus and posterior crus, and the bottom section is referred to as the footplate. It is this footplate that is essential in transmitting sound to the inner ear. The stapes is held in place by the stapedius muscle which is connected to the facial nerve.
The stapes is first seen in a human embryo between the sixth and eighth weeks of life. During this time, it surrounds the stapedial artery which is providing most of the vasculature of the embryonic head. Later in embryonic development, the vasculature of the head is provided by the external carotid artery, and the stapes is left with its window-like opening in the middle. A bone comparable to the stapes in humans are also found in non-mammalian creatures where it is called the columella.
The stapes plays an essential role in the transmission of sound through the ear. When something prevents the stapes from functioning properly, it has serious consequences for the auditory system. Otosclerosis is a common culprit in hearing loss because it causes the stapedial footplate to become fixed. When this occurs the stapes is unable to transmit vibrations efficiently.
Hearing loss due to fixation of the stapedial plate can sometimes be corrected with a surgery called stapedectomy. This surgery involves removing a portion of the stapes and replacing it with a prosthetic piece. Better nutrition and fluoridation of drinking water have all but eliminated this problem in many parts of the world.
