The Ear (Lectures 22 & 23) Flashcards
1
Q
Regions of the war
A
- external ear (sound receptions)
- middle ear
- inner ear
2
Q
External ear
A
- auricle or pinna is like a funnel for the ear canal
- external acoustic meatis or ear canal= small tube to direct sound waves to the ear drums
-ear drum= tympanic membrane
• the deepest part of the ear - tympanic membrane
• thin, sensitive
• epithelial tissue
• last part of external ear
3
Q
Middle ear
A
- in temporal bone
- tympanic cavity = air filled
• pressure inside the cavity can be regulated by the auditory tube (eustachian tube) - Eustachian tube is a connection between the frost and middle ear cavity
• allows you to equalize the pressure of middle ear cavity and outside air
• need this when the bodies change height rapidly
4
Q
Middle ear cavity
A
- in the middle ear cavity the three smallest bones in the body
• malleus
• incus
• stapes
- covers the oval window= the entrance into the inner ear
- functions
• transfer energy to inner ear
• transfers sound energy
5
Q
Pathway of sound for hearing
A
- between the middle ear bones are synovial joints
** smallest synovial joints in the body
6
Q
Inner ear
A
- hearing and balance
- completely inclosed in the temporal bone
Labyrinth - bony
• outer labyrinth- cochlea : hearing (only part for hearing)
- vestibule: balance
- semicircular canals: balance
• membranous - inner labyrinth, thin epithelial tissue
- inner ear filled with lymph fluids
Lymphs
- endolymph
• fluid inside membranous labyrinth - perilympth
• between membranous and bony labyrinth
7
Q
Structure of cochlea
A
- hearing only
- long hollowed tube that is coiled
- 3 fluid filled cavity spaces
• Scala vestibuli: filled with perilymph
• Scala tympani: filled with perilymph
• cochlear duct: filled with endolymph - Spiral organ: structure that is sensitive to sounds and can detect sounds
8
Q
Spiral organ
A
- is sensitive to sounds and can detect sounds
- also called organ of corti
- has hair cells called sterocilia (microvilli)
• to stimulate cell you have to move the sterocilia
*• sterocilia is embedded in the tectorial membrane - tectorial membrane: sits on top of hair cells
- basilar membrane
• sound energy through the basilar membrane
vibrates this causes the hair cells to move
*** cochlear nerve going to CN VIII for hearing only
** high frequency sounds enter the spiral organ close to the oval window and low frequency sounds enter the spiral organ farther away
** the cochlear nerve contacts hair cells of the spiral organ
9
Q
Two structures important for balance
A
- Vestibule
- Crista ampullaris
10
Q
Vestibule
A
- stationary position and linear movements of head
- evaluates position of head relative to gravity
- detects linear acceleration and deceleration
- utricle and saccule: two sacks inside vestibule
• made of hair cells/ gelatinous covering on top of hair cells ( otolithic membrane)
• macula: hair cells embedded in otolithic membrane containing otoliths
• detects speeding up and slowing down/ does not detect constant movement
-
11
Q
Otoliths
A
- dense particle inside of otolithic membrane
• very heavy/ gravity can easily move them
• give membrane enersha ( resist movement)
12
Q
Vestibule in maintains balance
A
13
Q
Rotational movements of head
A
- evaluates movement of head (angular acceleration)
-3 semicircular canals
• ampullae
- crista ampullaris
- hair cells
- cupula: gelatinous membrane, moves the hair cells, no gravity, enertia - ** cochlear nerve: cochlea, sound only
- ** vestibular nerve: vestibule, semicircular canals
14
Q
Semicircular canals
A
-Verticals and horizontal
-3 swollen ends of semicircular canals= ampulla
• inside is the sensory structure
• crista ampullaris
• inside ampulla detect rotational movement of the head
• hair cell inside crista ampullaris
15
Q
Points to remember
A
- inner ear functions for hearing and balance
- sound waves enter the external auditory canal, impact tympanic membrane, vibrate inner ear ossicles, strike oval window, create waves in perilymph of scala vestibuli, increase pressure in endolymph in cochlear duct, membrane supporting hair cells vibrate, hair cells stimulated, vibrations transferred to perilymph of scala tympani, travel to round window and dampened.
