The mastoid bone is a part of the temporal bone located behind the ear. It has a honeycomb-like structure filled with air cells, which help to regulate air pressure in the middle ear. The mastoid process, a prominent bony projection, serves as an attachment point for neck muscles. In addition to its role in hearing, the mastoid bone is important for protecting the inner ear and supporting the surrounding structures. Infections in the middle ear can sometimes spread to the mastoid bone, leading to a condition known as mastoiditis, which may require medical treatment.