Ears: Facts, Function & Disease
by Alina Bradford, Live Science Contributor | September 24, 2015 12:07am ET
The ear isn’t just the hearing organ. It is a complex system of parts that not only allows humans to hear, but also makes it possible for humans to walk.
Size
Ears come in many shapes and sizes. Typically, men’s ears are larger than women’s, according to a study in the journal Plastic and Reconstructive Surgery. Researchers also found that the average ear is about 2.5 inches (6.3 centimeters) long, and the average ear lobe is 0.74 inches (1.88 cm) long and 0.77 inches (1.96 cm) wide. They also noted that the ear does indeed get larger as a person ages.
Another study at Texas Tech University confirmed this observation. The study found that as people age, the ear's circumference increases on average 0.51 millimeters per year, likely due to aging changes of collagen. A correlation between age and ear circumference can be put into an equation: Ear circumference in mm = 88.1 + (0.51 x subject's age). Conversely, a person’s age can therefore be calculated by the size of a person’s ear, using the equation: Subject's age = 1.96 x (Ear circumference in mm – 88.1)
Function
The ear has three main parts: external ear, middle ear and inner ear. They all have different, but important, features that facilitate hearing and balance.
Hearing
The external ear, also called the auricle or pinna, is the loop of cartilage and skin that is attached to outside of the head. It works much like a megaphone. Sound is funneled through the external ear and piped into the external auditory canal, according to Nebraska Medicine. The auditory canal is the part of the ear hole that can easily be seen when looking an ear up close.
The sound waves pass through the auditory canal and reach the tympanic membrane, better known as the eardrum. Just like a drum being hit be a drumstick, the thin sheet of connective tissue vibrates when sound waves strike it.
The vibrations pass through the tympanic membrane and enter the middle ear, also called the tympanic cavity. The tympanic cavity is lined with mucosa and filled with air and the auditory ossicles, which are three tiny bones called the malleus (hammer), incus (anvil), and stapes (stirrup), according to Encyclopedia Britannica.
As the bones vibrate, the stapes pushes a structure called the oval window in and out, according to the National Library of Medicine (NLM). This action is passed on to the inner ear and the cochlea, a fluid-filled, spiral-shaped structure that contains the spiral organ of Corti, which is the receptor organ for hearing. Tiny hair cells in this organ translate the vibrations into electrical impulses that are carried to the brain by sensory nerves.
Balance
The Eustachian tube, or pharyngotympanic tube, in the middle ear equalizes air pressure in the middle ear with the air pressure in the atmosphere. This process helps humans retain their balance.
The vestibular complex, in the inner ear, is also important to balance because it contains receptors that regulate a sense of equilibrium. The inner ear is connected to the vestibulocochlear nerve, which carries sound and equilibrium information to the brain.
Diseases & conditions
Ears are delicate organs that can often have problems due to damage, bacteria or even changes in the environment.
Ear infections are the most common illness in babies and younger children, according to the NLM. Common symptoms of ear infections are drainage from the ear, hearing loss, earache, fever, headaches, pain in the ear and a feeling of fullness in the ear, according to the American Academy of Family Physicians.
Meniere's disease a disease of the inner ear that may be the result of fluid problems inside the ear. Symptoms include hearing loss, pressure or pain, dizziness and tinnitus. Tinnitus is a roaring in the ears. It can also be caused by loud noises, medicines or a variety of other causes.
Ear barotrauma is an injury to the ear due to changes in barometric or water pressure, according to the NLM. It typically occurs during flights in an airplane, traveling to places at high altitudes or diving into deep waters. Symptoms include pain, stuffy ears, hearing loss and dizziness. Barotrauma can usually be fixed by “popping” the ears by yawning, chewing gum or trying to blow outward while keeping the nose pinched and mouth closed.
Ear wax, also called cerumen, has antibacterial properties and also lubricates and protects the ear. Normal amounts shouldn’t bother most people, though sometimes, wax can build up and should be removed, according to The American Academy of Otolaryngology. Symptoms of wax build-up is a feeling of blockage in the ears, coughing, odor, discharge, itching and hearing loss.
Hearing typically declines with age naturally, though damage to the ear can cause hearing loss at a very young age. “We are seeing more and more patients with significant hearing loss as early as the late teenaged years," Dr. Sreekant Cherukuri, a board-certified otolaryngologist based in Chicago and the founder of MDHearingAid, told Live Science. "Noise-induced hearing loss is a growing problem in this country. We are connected to phones and music players, often for hours each day. When our ears are exposed to harmful noise, delicate cells in the inner ear become damaged. Unfortunately, the damage is cumulative over time.”
Promoting good ear health
Once hearing is gone, it is impossible to repair it naturally. Most patients with hearing loss need surgery or hearing aids. “The good news is that this is 100 percent preventable," said Cherukuri. "I tell my patients to follow the 60-60 rule when they use earbuds or headphones: no more than 60 percent of full volume for no longer than 60 minutes at a time."
People who participate in noisy activities or hobbies, such as sporting events, music concerts, shooting sports, motorcycle riding or mowing the lawn, should also wear earplugs or noise-canceling or noise-blocking headphones to help protect the ears.
Careful cleaning is another way to prevent hearing loss and damage. The American Academy of Otolaryngology suggests cleaning the external ear with a cloth. Then, put a few drops of mineral oil, baby oil, glycerin, or commercial drops in the ear to soften the wax and help it drain out of the ear. A few drops of hydrogen peroxide or carbamide peroxide may also help. Never insert anything into the ear.
taken from: http://www.livescience.com/52287-ear-anatomy.html
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