The Sense of Hearing
So many of us take for granted the ability to listen to our favorite music, the sound of birds singing outside our windows or the first sounds of crying made when our own child is born. The sense of hearing is a wonderful thing and probably the easiest of the five senses to lose.
The sense of hearing is conducted by the ears. In addition to the sense of hearing, the ears are also involved in the sense of balance. Therefore, you get two senses today for the reading of one.
The ears are divided into five parts:
I. Outer Ear – The outer ear consists of the large visible part of ear to the outer surface of the eardrum.
A. Pinna – The pinna, also known as the auricle is the large section of the ear visible on the side of the head. It is composed mostly of cartilage and skin. The cartilage is shaped with ridges and channels that are perfectly designed to catch sound waves and funnel them into the ear canal.
B. Ear Canal – The ear canal, also known as the external auditory meatus, is the open channel that carries the sound waves to the outer surface of the ear drum.
C. Wax Gland – The wax gland, also known as the cerumen gland secretes a waxy secretion into the ear canal. Some evolutionists believe this gland to be a vestigial sweat gland located in the ear, but audiologists (ear doctors) will tell you that the waxy secretion acts to keep the inner ear lubricated. It also traps dust and other particles to prevent them from reaching and damaging the ear drum.
D. Ear Drum – The ear drum, also known as the tympanic membrane is an extremely sensitive thin membrane that vibrates in response to any sound waves that strike it.
II. Middle Ear – The middle ear starts on the inside surface of the ear drum and is an air filled chamber that converts the sound waves into mechanical energy. It consists mainly of the three smallest bones in the human body. As the ear drum vibrates in conjunction with the sound waves that hit it, it transfers those vibrations to the malleus which in turn works the incus and stapes. The stapes has a stirrup shaped end with a flat stapes plate which is attached to the oval window which leads to the inner ear.
A. Malleus – The malleus, also known as the hammer, has a broad end that attaches to the backside of the ear drum on one end and to the incus on the other.
B. Incus – The incus, also known as the anvil, is the middle bone in the ear. It connects to the malleus on one end and to the stapes on the other.
C. Stapes – The stapes, also known as the stirrup, connects to the incus on one end and to the oval plate on the other.
D. Oval Plate – The oval plate, also known as the oval window, is a thin plate separating the air filled middle ear and fluid filled inner ear. The oval plate acts like an amplifier as it transmits the sound vibrations from the bones of the middle ear into the inner ear.
E. Eustachian Tube – The Eustachian tube is not directly connected to the sense of hearing, but can affect it. The tube runs from the middle ear to pharynx. It helps regulate the air pressure in the middle ear. When the Eustachian tube is blocked, the air pressure inside the middle ear can differ from the air pressure outside the ear resulting in muffled hearing or in some cases, intense pain. When the tube is opened up again, it allows the middle ear pressure to equalize with the outside pressure. Most people refer to this as popping their ears.
III. Inner Ear – The inner ear, also known as the labyrinth, houses the hearing and balance sensory organs. Unlike the middle ear, the inner ear is fluid filled.
A. Cochlea – The cochlea is a fluid filled spiral shaped tube that resembles a snail. The cochlea tube is divided into three smaller fluid filled tubes.
1. Cochlear Duct – The cochlear duct, also known as the median canal, is the central of the three smaller canals of the cochlea. This canal is filled with a fluid known as endolymph. Endolymph is a fluid that has a higher concentration of potassium ions which are involved in creating a electrochemical gradient with the tympanic canal. The cochlear duct contains a structure known as the organ of Corti or the organ of hearing.
a. Organ of Corti – The organ of Corti runs the length of the cochlear duct. It contains sensory hair cells that react to the sound vibration transmitted by the middle ear and converts them to action potentials or electric impulses. Different sensory hair cells detect different pitches and frequencies, thus distinguishing sounds in such a way as to allow one to appreciate beautiful symphony or the sound of their child’s first words.
2. Tympanic Canal – The tympanic canal is the largest of the three canals and is filled with a perilymph fluid. Perilymph fluid is comparable to plasma and has a higher concentration of sodium ions which helps establish a electrochemical gradient between it and the endolymph fluid filled cochlear duct. As the oval plate vibrates, it causes the fluid in the tympanic and vestibular canals to move. This fluid movement is detected by the sensory hair cells in the cochlear duct, which are then interpreted as sound.
3. Vestibular Canal – The vestibular canal, like the tympanic canal is filled with perilymph fluid and functions similarly to the tympanic canal.
B. Semicircular Canals – There are three semicircular canals that are attached to the back of the cochlea. They are set at right angles to each in a three dimensional array, much like an X, Y and Z axis on a three dimensional graph. They are filled with endolymph fluid and also have sensory hair cells located along their inner curved surfaces. When the head moves in any direction, it causes the fluid in these canals to move and stimulate the sensory hair cells allowing the brain to interpret in what angle or direction the head moves. The semicircular canals are critical to maintaining our sense of balance.
C. Utricle and Saccule – the utricle and saccule are two fluid filled sacs located at the base of where the semicircular canals and cochlea connect. They contain endolymph fluid and are responsible for our sense of acceleration and deceleration. For example, when you are in an airplane taking off, you can feel the plane accelerate down the runway for takeoff. They also let you know when the plane comes to a faster then normal stop when landing.
IV. Acoustic Nerve – The acoustic nerve carries the impulses generated by the cochlea to the brain where it deciphers the impulses into the sounds we hear.
The ear along with the senses of hearing and balance are very ingeniously designed. When one part of this system is not functioning properly, it can not only cause a loss of hearing, but can also completely destabilize a person’s sense of balance.
I recall when I was a kid on the farm in Illinois; I got stung in the ear canal by a wasp. Not only did it hurt like the dickens, but the ear canal swelled shut for several days and I could not hear out of that ear. As a young child, it was very scary. Later in life, I’ve had several severe middle and inner ear infections. Like the wasp sting, they were very painful and muffled my hearing in the infected ear. Worse though was the sense of dizziness that I had for several days. Any slight movement of my head made me feel like the room was spinning, which not only made it very difficult to walk but also made me very sick to my stomach.
When we look at the structures involved in hearing and balance, they all have indications of being a exquisitely designed by an intelligent engineer. From the sound capturing outer ear to the intricate and delicate bones of the middle ear to the amplifier between the middle and inner ear to the unique structures of the cochlea and semicircular canals.
Evolutionists will argue that there is an evolutionary progression of ear structure that leads from primitive to our finely tuned features. We would argue that these are not evidence of evolutionary progression, rather God designed each ear and hearing structures just right for each kind of animal to fit its needs.
William Tyndale tops King Henry VIII’s “Most Wanted” list in 1535 and is being pursued across Europe by the king’s bounty hunters. What is his crime? Murder? Theft? No, none of these. William Tyndale’s “crime” is translating the Bible into English for the common people. Is he willing to risk his life for this cause?
This episode of The Torchlighters follows William Tyndale’s adventures as he works in secret, moving from town to town as a fugitive to avoid capture. Friends and allies help him along, but enemies may be lurking around any corner. Come along and see whether this Torchlighter completes his task before the king’s men close in on him.
The Torchlighters is an ongoing series of animated programs with strong values and educational content for youth ages 8-12. Each Torchlighters episode presents the story of a true-life hero from Christian history. Kids will see what God can do through a “Torchlighter” and will be challenged to carry their own torch while learning about the history of our faith.
- English and Spanish languages with optional English subtitles
- Stimulating interview with Dr. David Daniell, Tyndale scholar
- Fascinating interview with actor Russell Boulter, voice of Tyndale
- Comprehensive leader’s guide with background information, timeline of the period, additional resources, and more.
- Reproducible student handouts, including comprehension and discussion questions, puzzles, activities, coloring, and more.