Module 1 The Nervous System

Lesson 1.1.6

1.1.6 page 2

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Outer Ear

outer ear: one of the three main regions of the ear which consists of the pinna and the auditory canal; ends at the tympanum or eardrum

middle ear: one of the three main regions of the ear which begins just past the tympanum and consists of a chamber containing three tiny bones (ossicles) called the malleus (hammer), the incus (anvil), and the stapes (stirrup); leads into to a minute opening called the Eustachian tube

inner ear: one of the three regions of the ear that is located deepest in the head and consists of a fluid filled chamber which contains the semicircular canals, the utricle, the saccule, and the cochlea

pinna: the outer flap of the ear; composed of skin and cartilage and shaped so that it enhances sound vibrations and funnels them into the auditory canal

vestigial: small or imperfectly developed part or organ which was once more fully developed in an earlier stage of the individual

There are three major regions in the ear: the outer ear, the middle ear, and the inner ear the most obvious structure of the outer ear is the pinna. Some animals can move their pinnae to maximize trapping sound waves. By moving its pinnae, the fennel fox, pictured on the right, can pinpoint with great accuracy the direction from which a sound originates. For many animals survival can be dependent on early detection of sound. In humans, the muscles of the pinna are vestigial, or nonfunctional, and we can’t move our pinnae. However, people sometimes cup their ear with their hand to simulate an enlarged pinna in order to hear better. Do you know anyone who can actually move their pinnae?

Fennec fox with very large ears (pinnae).

A buildup of wax in the auditory canal which interferes with conduction of sound waves toward the tympanum has to be removed by a physician by using a syringe. Never try this on your own.

Read page 420 and note "Figure 12.20."

Self-Check

auditory canal: a short channel that conducts sound waves from outside the ear to the tympanum (eardrum); amplifies or makes sounds louder

tympanum: a round elastic structure located in the middle ear that vibrates in response to sound waves; also called the eardrum or tympanic membrane

Locate the pinna and the auditory canal. What is the function of these structures?

What did cupping the ear accomplish?

The auditory canal also produces ear wax. What is the purpose of this wax?

What else does the auditory canal do?

Wax build up can be a cause of conductive deafness. Look at the picture on the right. What is the syringe used for?

The auditory canal ends at the tympanum, also known as the tympanic membrane, or more commonly the eardrum. Can you hypothesize what the function of the tympanic membrane might be?

To review the structures found in the outer ear and their functions, read pages 419 – 420 in your textbook. Summarize your findings in a table similar to the one below. File the table in your course folder for later access.

The Structures and Functions of the Outer Ear

Structure	Function(s)

Check your work.

Self-Check Answers

collect and direct sound waves

collected and directed more sound waves

moistens passage and ear drum for flexibility, collects debris

channels out debris, directs sound to the tympanic membrane

uses warm water to float out and remove wax build-up

sound waves cause it to vibrate; converts sound energy to mechanical energy