Ear (Encyclopedia of Science)
The human ear is the organ responsible for hearing and balance. The ear consists of three parts: the outer, middle, and inner ears.
The outer ear collects external sounds and funnels them through the auditory system. The outer ear is composed of three parts, the pinna (or auricle), the auditory canal, and the eardrum (tympanic membrane).
What are commonly called earshe two flaplike structures on either side of the headre actually the pinnas of the outer ear. Pinnas are skin-covered cartilage, not bone, and are therefore flexible.
The auditory canal is a passageway that begins at the ear and extends inward and slightly upwards. In the adult human it is lined with skin and hairs and is approximately 1 inch (2.5 centimeters) long. The outer one-third of the canal is lined with wax-producing cells and fine hairs. The purpose of the ear wax and hairs is to protect the eardrum (which lies at the end of the canal) by trapping dirt and foreign bodies and keeping the canal moist.
The eardrum is a thin, concave membrane stretched across the inner end of the auditory canal much like the skin covering the top of a drum. The eardrum marks the border between the outer ear and middle ear. In the adult human, the eardrum has a total area of approximately 0.1 square inch (0.6 square centimeter). The...
(The entire section is 1455 words.)
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