Ear (Ch. 19)

Question 1

What are the 3 parts of the ear?

Answer 1

External ear, middle ear, and inner ear

Question 2

External Ear: what is the Auricle?

Answer 2

The auricle (or pinna) is mostly elastic cartilage covered with skin. It’s the structure attached to the head that we refer to as the ear.

Question 3

External Ear

Answer 3

Auricle (or pinna) gathers sound waves and funnels into EAM. Mostly elastic cartilage covered w/ skin.

EAM is short tube running from auricle to eardrum. Lined w/ hairs, sebaceous glands, and ceruminous glands (produce earwax) to keep dust and insects out.

Question 4

Tympanic Membrane

Answer 4

aka eardrum

Boundary between external and middle ear
Sound waves entering EAM hit eardrum, cause it to vibrate

Question 5

Middle Ear

Answer 5

Air-filled space medial to eardrum

Located in petrous part of temporal bone

Holes in bony wall between middle and inner ear = round window and oval window

Question 6

What are the 3 bones of the middle ear?

Answer 6

Malleus (hammer)
Incus (anvil)
Stapes (stirrup)

Question 7

Middle Ear Ossicles (bones)

Answer 7

Smallest bones in body

Transmit vibrations form eardrum across middle ear cavity and to inner ear (eardrum vibrates against malleus; stapes vibrates against oval window)

Question 8

Muscles of the Middle Ear

Answer 8

2 muscles in middle ear help stabilize ossicles during very loud sounds:

• -tensor tympani (attached to malleus)
• -stapedius (attached to stapes)

Question 9

Middle Ear: Pharyngotympanic Tube

Answer 9

Pharyngotympanic tube (or auditory tube) connects middle ear to pharynx

Allows equalization of pressure on both sides of tympanic membrane

Question 10

Otitis Media

Answer 10

“middle ear infection”

Infection from throat (via pharyngotympanic tube)

Fluid buildup; common in children

Question 11

Inner Ear

Answer 11

aka Labyrinth

Bony labyrinth: cavity consisting of semicircular canals, vestibule, and cochlea

Membranous labyrinth: walls and sacs within the bony labyrinth

Question 12

List the 3 parts of the inner ear and their functions.

Answer 12

1. Cochlea: hearing
2. Vestibule: equilibrium (acceleration)
3. Semicircular Canals: equilibrium (rotation)

Question 13

Cochlea

Answer 13

hearing

Cochlea looks like a snail shell

Cochlear Nerve (part of Vestibulocochlear Nerve) runs through center of modulus (axis of cochlea)

Question 14

Cochlear Duct

Answer 14

Cochlear duct (aka Scala Media) - part of membranous labyrinth that contains sensory receptors for hearing

Roof is the vestibular membrane

Floor is basilar membrane

Question 15

Basilar Membrane and Spiral Organ

Answer 15

Basilar membrane supports spiral organ (organ of Corti)

Spiral organ has hair cells (cilia). When basilar membrane moves, cilia bend/distort, triggering impulses

Question 16

Vestibule and Semicircular Canals

Answer 16

Vestibule has a Utricle and Saccule (expansions of the labyrinth)

These have Maculae. When head tilts, Otoliths (small crystals) embedded in gelatinous layer of maculae move, and hairs bend

Question 17

Semicircular Canals and Ampullae

Answer 17

Semicircular canals are at right angles to each other. Expansion at end is Ampulla (receptor for movement). When head rotates, Endolymph in canals move, cupula within ampulla bends, triggering cilia.