Inside this inner ear is a fluid-filled, snail-shaped structure. In them, the jaw transmits sound vibrations directly to the inner ear. Snakes, for instance, lack both the outer ear and the middle ear. Not all animals, however, have those ossicles. The stapes (STAY-pees), for instance, is only 3 millimeters (0.1 inch) long! These three bones work together to receive sound waves and transmit them on to the inner ear. In people, these three bones are known as ossicles. Those bones are the malleus (which means “hammer” in Latin), the incus (which means “anvil” in Latin) and the stapes (which means “stirrup” in Latin). Inside the middle ear is a small cavity with three tiny bones. This triggers pressure waves that swell into the middle ear. As sound waves slam into this ear drum, they vibrate its membrane. This tight membrane stretches across the end of the ear canal. In animals with an outer ear and ear canal, the ear drum - or tympanum - is inside the head. Many frogs, for example, just have a flat spot behind their eyes. Not every animal has an outer ear and ear canal. In people, this tiny tube is about 2.5 centimeters (1 inch) long. Along the way, the shape of the ear helps to amplify the sound - or increase its volume - and determine where it’s coming from.įrom the outer ear, sound waves travel through a tube called the ear canal. The outer ear’s shape helps to collect sound and direct it inside the head toward the middle and inner ears. These aspects of the wave cause whatever a sound hits to vibrate.
As a wave stretches back out, it pulls on the tissue. The compression exerts a push on objects, such as ear tissue. Sound travels through the air in waves that compress, stretch and then repeat. ISSN 2002-4436/Wikimedia Commons (CC BY 3.0) Adapted by L. “Medical gallery of Blausen Medical 2014”. Signals from these cells head to the brain. INTERNAL EAR:In the inner ear, sound waves vibrate tiny hair cells in the snail-shaped cochlea.
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