What is the smallest bone in the human body?
The stapes, a tiny bone in the middle ear, is the smallest bone in the human body. It is about 3 millimeters long, roughly the size of a grain of rice.
The stapes is one of three tiny bones in each middle ear, together called the ossicles. The other two are the malleus and the incus, also known as the hammer and anvil. The stapes is named after its shape, which looks like a stirrup.
When sound waves reach the eardrum, it vibrates. The three ossicles pass these vibrations along, and the stapes pushes on a small membrane called the oval window. This sends waves through the fluid of the inner ear, where hair cells turn them into nerve signals.
Why size matters
The ossicles act like a lever, increasing the force of the vibrations so that sound can move efficiently from air into fluid. Their small size lets them respond to very fast vibrations, which is important for hearing high-pitched sounds.
Did You Know?
The ossicles are the only bones that are almost fully adult-sized at birth.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.