November 13th, 2004
The Beating Eardrum
Normal Ear
The eardrum is a thin piece of skin that's stretched tightly. It vibrates like a drum when sound hits it. There are three very delicate bones in the ear, known as ossicles: the malleus which looks like a hammer, the incus which looks like an anvil, and the stapes which looks like a stirrup. There is an opening in the stapes called the oval window. The end of the stapes that opens into the inner ear is called the round window and is extremely smaller than the beginning of the opening (oval window). Connected through the round window of the stapes is the cochlea, which looks like a snail and is filled with fluid. There are little hair cells on the bottom membrane of the cochlea. Each hair cell has even smaller hair like fibers called cilia. These cilia detect the vibrations in the fluid.
(courtesy of http://www.cartage.org.lb)
The eardrum is a thin piece of skin that's stretched tightly. It vibrates like a drum when sound hits it. There are three very delicate bones in the ear, known as ossicles: the malleus which looks like a hammer, the incus which looks like an anvil, and the stapes which looks like a stirrup. There is an opening in the stapes called the oval window. The end of the stapes that opens into the inner ear is called the round window and is extremely smaller than the beginning of the opening (oval window). Connected through the round window of the stapes is the cochlea, which looks like a snail and is filled with fluid. There are little hair cells on the bottom membrane of the cochlea. Each hair cell has even smaller hair like fibers called cilia. These cilia detect the vibrations in the fluid.
(courtesy of http://www.cartage.org.lb)
How do we hear?
We hear when sound waves travel into our ears and vibrate on the tympanic membrane, or the eardrum. The vibrations pass through the three bones in the ear, from the eardrum to the cochlea. The cilia of the hair cells in the cochlea touch the top membrane of the cochlea. The vibrations of the sound waves in the fluid (in the cochlea) cause the top and bottom membranes of the cochlea to flex up and down, making the hair cells excited. Once excited, they create a message and send it to your brain through the auditory nerve. Your brain then interprets the sound you are hearing.
Ear Infection
Ear infections, also known as otitis media, are caused by fluid in the middle ear, which breeds bacteria and viruses and leads to infection. The fluid is believed to accumulate in the ear from the connection between the nose and mouth, called the Eustachian tube. The tube in children is shorter and more horizontal so the bacteria from the nose has a better chance of travelling into the ear than adults. The bacteria is usually from the common cold. The bacteria causes the tube to swell and fluid buildup behind the eardrum. With the fluid building up, it becomes a thick pus blockup in the middle ear. This causes your ear to hurt! However, when you age, the chances of you developing and ear infection decreases significantly.
Perforated Eardrum
When you have a hole in your eardrum, or your eardrum ruptures, it is called a "perforation" in your eardrum. This can be caused by an infection and many different kinds of trauma, include being hit in the ear with a flat hand, using a q-tip stuck too far into the ear, an explosion, or getting acid in your ear. The larger the perforation, usually the greater the damage. When this happens, a person usually looses some hearing and occasionally has some discharge. Eardrum perforations usually heal on their own, but it can take up to a couple months. The ear must be covered in order to prevent water getting in and causing an infection. If the perforations do not heal by themselves, they must be fixed by surgery (but not to worry, it's not that common).
Ear Infection
Perforated Eardrum
NOW YOU CAN MAKE YOUR OWN EARDRUM!!!!!!
It is
really simple and FUN to make your own eardrum.
All you need is a bowl, plastic wrap, uncooked rice grains, and a boom box.
*Tightly wrap the plastic
wrap around the top of the bowl.All you need is a bowl, plastic wrap, uncooked rice grains, and a boom box.
*Place 20-30 rice grains on top of the plastic wrap covering the bowl.
*Now with your favorite music playing, place the boom box next to your bowl. The sound waves from the boom box will cause the rice to vibrate on the plastic wrap, just like sound waves cause your ear drum to vibrate.
*You can demonstrate how ear infections work by filling up your bowl with shaving cream. Now when you put the boom box up to the bowl the rice grains do not jump up and down.
*If you punch a small hole in the plastic wrap the rice will not jump up and down when the boom box is near the bowl. This demonstrates how your hearing is not as effective if you perforate your ear drum.
Materials:
4" to 20" in diameter sturdy bowls
plastic wrap
shaving cream
uncooked rice
boom box
How to Protect your Ears!
Kids Judge Home
More Ear Infection Information
Ear Anatomy
Perforations