Anatomy of The Ear’s External Structures
Talking to Your Friend on the Phone
Let’s say something really interesting happened to you today. You dial your friend to tell her all about it. As you try to control your excitement, you tell her about how you got an A+ on a really hard exam. As you talk, sound waves leave your mouth and are transmitted over the phone to your friend’s phone, where her phone’s speaker sends sound waves that reach her ears.
There are several important structures involved in the sensation of hearing that your friend is about to experience. As the sound waves reach her ears, external, middle, and inner parts of her body’s hearing apparatus become involved in hearing. In this lesson, we will delve into the important parts that make up the external ear, the first step in the ability to hear sounds.
As the sound waves leave your friend’s speaker, they go to her body’s first ‘device,’ so to speak, which captures the sound waves floating through the air. This structure captures, amplifies, filters, and directs sound waves into the more inner parts of the auditory system. This anatomical part is called the pinna. It is sometimes referred to as the ‘auricle.’
Basically, the pinnae, the plural form of pinna, are the two things sticking out of the sides of your head – what we commonly call the ears.
The External Auditory Meatus
Once the pinna captures the sound, amplifies it, and filters it, it will then direct the sound waves into the external auditory meatus, which is a really fancy word for your ear canal – the place where all of that icky earwax builds up. The word ‘meatus’ (in external auditory meatus) is nothing more than a fancy word for an opening or a channel. Think of the external auditory meatus as a tube that connects the pinnae to the eardrum.
The Eardrum and Tympanic Membrane
Speaking of the eardrum, it has another important name: the tympanic membrane. The tympanic membrane is a thin membrane that transmits sound waves from the external ear to the middle ear.
The sound waves captured by the pinna and transmitted by the ear canal eventually reach the tympanic membrane. Once they reach the eardrum, the sound waves essentially bang on the eardrum like you would bang on the drums with drumsticks. This banging on the eardrum eventually changes the vibration of sound waves in air into vibrations in the fluid that fills your inner ear. Therefore, the function of the eardrum is to help convert and amplify one signal, sound waves in air, into another: sound waves in fluid.
This conversion is critical for the further alteration of sound waves in fluid into an electrical signal – the only signal by which your brain can actually process and interpret the original sound waves occurring in the air around you.
Hopefully, your brain can interpret the sound waves coming out of my mouth right now, as it’s time to review the important parts of this lesson.
The pinna and the ear canal are all part of what is known as the external ear, while the tympanic membrane forms the boundary between the external ear and middle ear. Let’s review what they do in order to help your friend hear about the excellent grade you got on your exam.
As the sounds waves leave the speaker, the ear, known as the pinna, captures, amplifies, filters, and directs sound waves into the ear canal.
The ear canal, also known as the external auditory meatus, is a tube that directs the sound captured by the pinna to the eardrum.
The eardrum, known more formally as the tympanic membrane, is a thin membrane that transmits sound waves from the external ear to the middle ear.
This is the first part of a larger sequence in converting sound waves to recognizable sound that allows your friend to share in your excitement of getting a great grade on your exam!
At the end of this video, you’ll be able to describe the structures and functions of the pinna, external auditory meatus and tympanic membrane.