The Ear

The ear is an organ for hearing and balance. It consists of three parts: the outer ear, the middle ear, and the inner ear. The outer and middle ear mostly collect and transmit sound. The inner ear analyzes sound waves and contains an apparatus that maintains the body's balance. The outer ear is the part which is visible and is made of folds of skin and cartilage. It leads into the ear canal, which is about one inch long in adults and is closed at the inner end by the eardrum. The eardrum is a thin, fibrous, circular membrane covered with a thin layer of skin. It vibrates in response to changes in the air pressure that constitute sound. The eardrum separates the outer ear from the middle ear. The middle ear is a small cavity which conducts sound to the inner ear by means of three tiny, linked, movable bones called "ossicles." These are the smallest bones in the human body and are named for their shape. The hammer (malleus) joins the inside of the eardrum. The anvil (incus) has a broad joint with the hammer and a very delicate joint to the stirrup (stapes). The base of the stirrup fills the oval window which leads to the inner ear. The inner ear is a very delicate series of structures deep within the bones of the skull. It consists of a maze of winding passages, called the "labyrinth". The front (see cochlea) is a tube resembling a snail's shell and is concerned with hearing. The rear part is concerned with balance. "Keeping one's ear to the ground" means to keep up on current trends. The phrase dates back to early 20th century politicians and comes from frontier lore of both pioneers and Indians, who listened for the sound of approaching hoofbeats.