How the Ear Works: Its Anatomy and Function
There are three main parts to the ear: the outer ear, middle ear, and inner ear. The outer ear consists of the pinna or auricle and the ear canal. The ear canal is shaped like a curved tube and at one end lies the eardrum. The eardrum serves to separate the ear canal from the middle ear space, which contains the three bones of hearing. These bones, the malleus (hammer), incus (anvil), and stapes (stirrup), are connected to one another. The malleus is also stuck to the eardrum while the base of the stapes (an area known as the footplate) sits on top of the inner ear. The inner ear (termed the labyrinth) contains compartments filled with fluid and specialized sensory cells. When sound waves vibrate the eardrum, the hearing bones transmit this to the fluid of the inner ear, ultimately creating a nerve impulse that travels through the hearing nerve to the brain.
The middle and inner ear are housed deep within the temporal bone, a complex bone that makes up the side of the skull. The mastoid cavity, a part of the temporal bone, is a honeycombed area that sits behind the ear canal and opens into the middle ear. In addition, the semicircular canals (which are specialized balance organs of the inner ear) are found within the mastoid cavity.
The nerves of hearing and balance, as well as the facial nerve (the nerve that controls movement of the face, supplies taste to the front 2/3 of the tongue, and helps create tears and saliva) all travel from the brain to the ear in another small channel, termed the internal auditory canal, located deep within the temporal bone.
The brain lies within the skull and is bathed in spinal fluid. The brain and its fluid are surrounded by a tough, water-tight covering called the dura mater. The area of the brain known as the temporal lobe actually sits on the petrous bone, another portion of the temporal bone. This petrous bone, therefore, serves to physically separate the brain from the ear canal, middle and inner ear, and mastoid cavity.
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