Unit Study: "I Can't Hair You!"

"Hair helps me hear? What did you say? I can't hair you!"

I said, "Hair helps you hear." It is the hair inside your ears that relays sounds to your brain. Don't believe it? Well, let's find out. Let's start from the beginning. For this study you will need a project notebook, drawing paper and pencils, and books about the ear. So start with a trip to the library. Find books about ears and hearing. Look particularly for one on the subject of deafness.

Your ears have three main parts: the outer ear, the middle ear and the inner ear. We will study each of these parts and their role in the marvelous process of hearing. Divide your study and notebook into three sections.

Part I. The Outer Ear
The outer ear part called the auricle is the part we all see, the fleshy curved part of the ear outside of the head. It has no bones but is supported by cartilage. Define cartilage. Find cartilage in a chicken and examine it.

A study of the three muscles that attach the ear to the head will teach us a difference in the function of the ears of humans as opposed to some animals that use the muscles to turn their ears in the direction of sound. Why is this important? What does it tell us about the human sense of hearing? Why is the human ear shaped as it is?

The ear canal or external auditory canal is the second part of the outer ear and is the opening and passageway that leads to the eardrum. It is about one inch long and has hairs, sweat glands and glands that produce earwax. How does earwax help protect your ears? Is it good or bad? When can it be harmful? Write a short lesson for kindergarten students about how to protect their ears. Use the line; "Never stick anything smaller than your elbow into your ear." How should a child clean his ears? Younger students make an ear safety poster.

Part II. The Middle Ear
The tympanic membrane or eardrum separates the outer ear from the middle ear. It is a thin, round, tightly stretched membrane about 10 mm in diameter. What purpose does the eardrum serve besides this separation? Is it flexible? Does sound bounce off of the eardrum? Is it like a drum in function? What happens when a person's eardrum is punctured? How about if the eardrum ruptures due to infection? Would a rupture cause deafness?

The three smallest bones in the human body, the auditory ossicles, are in the middle ear. Draw sketches of them and label them with the Latin names, (malleus, incus and stapes) and the common names, (hammer, anvil and stirrup). How big is the stapes? Why are the bones so named? The hardest bone in the human body, the temporal bone, is also located in the ear. What is the temporal bone for?

The Eustachian tube connects the ear to the throat. What is the purpose of this tube? How does it help us with air pressure changes? When does it open and close? Draw these ear parts in your notebook and label them using colored pencils to differentiate the parts easily. There are two "windows" in the middle ear. Draw them. What are their functions?

Part III. The Inner Ear
The inner ear is called the labyrinth and has three basic parts, the vestibule, the semicircular canals and the cochlea. Two baglike sacs called the utricle and the saccule are found in the vestibule and each is lined with hair cells. Hair cells are specialized sense cells with tiny hairlike projections. These cells attach to nerve fibers. Remember, I mentioned earlier that hair that helps you hear! A membrane above the hair cells is embedded with mineral grains called otoliths.

The semicircular canals are called lateral, superior and posterior canals. Each duct widens and forms a pouch called the ampulla which has hair cells that are attached to nerve fibers. The canals and the utricle and saccule make up the ear's organs of balance.

The cochlea is the part of the inner ear that is coiled and shaped like a snail shell. It is about the size of a pea, but if it were uncoiled, the cochlea would be a little more than 1 1/2 inches long. Three fluid-filled ducts wind through the cochlea. One of these ducts is the cochlear duct and one wall of it is the basilar membrane which is covered with 15,000 hair cells. The hair cells are the organ of corti, which is the actual organ of hearing. The tectorial membrane is above the cells. The inner ear nerve known as the auditory nerve is made up of two branches--the cochlear nerve and the vestibular nerve.

Part IV. How Sounds Travel to the Brain
Sound travels in waves into your ear through the external canal and hits the eardrum causing it to vibrate. The vibrations travel across the ossicles. The footplate of the stapes vibrates against the oval window. These vibrations create waves in the fluid that fills the ducts of the cochlea in the inner ear. The fluid pushes against the basilar membrane and moves the hair cells of the organ of corti, which slide against the tectorial membrane. The hairs bend and create impulses in the fibers that are attached to the hairs. The cochlear nerve transmits these impulses to the temporal lobe of the brain. The brain interprets the impulses as sounds.

Part V. The Bible
The study of any subject is incomplete until we have seen what the Bible says about the subject. Find some scriptures for your notebook about hearing. Attempt to explain the meaning of the scripture that says, "Having ears they do not hear." In the book of Psalms, David asks God to "give ear." What does this mean? In Proverbs, we are taught to "incline" our ears. What does God want us to listen to? What does He warn us not to listen to? In the Gospels, a disciple tried to help Jesus by cutting off a soldier's ear with a sword. Jesus restored the ear. Write a story or poem about how this might have affected the soldier.

Part VI. Field Trips
· Visit an ear doctor's office.
· Take a virtual field trip on the Internet to learn what you can about the ear and how it works.
· Visit a classroom, school or home for the hearing impaired to see how they cope with hearing loss.
· Visit a church that provides sign language for deaf members. Try to learn some signs.

Part VII. Points for Further Study
Can a deaf person drive? What sorts of jobs would be open to deaf people? How can deaf people enjoy music that they cannot hear? Can a deaf person's other senses help compensate for their hearing loss? How does hearing loss affect balance? What medications can cause hearing loss? What injuries to the ear can disrupt hearing? Are children in homes where people smoke troubled with more ear problems? How can you protect your ears?

Find out about these ear diseases: otosclerosis, otitis, Meniere's disease and Presbycusis. Compare the ears of various animals such as frogs, birds, elephants or bats. How do they differ from the human ear? Otology is the science that deals with the ear and its diseases. Audiology is the science of hearing and deals with therapy for persons who are hearing impaired. What is the difference in the sciences of audiology and otology?

As a side study of medical importance, let's consider the custom of ear piercing. Many persons have the bone and cartilage free earlobe pierced for jewelry. Is this harmful? Can infections damage the ear lobe or hearing? Now consider the piercing of the cartilage parts of the ear which is popular today. Is this piercing damaging or can it be harmful? If you know people who have pierced ears question them. Record your findings on a probability chart. Interview a doctor, if possible, about the risks and problems caused by piercing cartilage. Some African tribes have used body piercings with graduated sizes of plugs to stretch ear lobes to huge proportions. Find photos that show the strange deformations of ear shape caused by this practice.

Ears and hearing are just two of the wonderful things God created and I hope that you have found this unit study "ear- resistible"!

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Elece Hollis is a freelance writer and stay-at-home mom. She and her husband Ron of 30 years have 7 children and are in their sixteenth year of homeschooling. They live east of Okmulgee, Oklahoma and south of Tulsa on a 40 acre pecan farm.

This article was originally published in the Sep/Oct '05 issue of Home School Enrichment Magazine. For more details, visit http://HomeSchoolEnrichment.com To request a free sample copy, visit http://homeschoolenrichment.com/magazine/request-sample-issue.html