The temporal bone is one of the two irregular bones on either side of the skull which form part of the lateral surfaces and base of the skull (the inferior sides of the cranium and part of the cranial floor). The lower region of the temporal bone is called the mastoid bone, a projecting portion of which is the mastoid process (see below).
The temporal bone has a remarkably complex internal structure and contains part of the ear canal, the middle ear, and the inner ear. The facial nerve, responsible for control of the facial muscles, winds through the temporal bone on its way from the brain to the face.
The mastoid process projects downward and forward from behind the ear. It is undeveloped in the newborn child and grows only as a result of the pull of the sternomastoid muscle (also called the sternocleidomastoid), as the child moves his or her head. It may be recognized as a bony projection at the end of the second year.