Lecture 20: Hearing And Equilibrium Flashcards
According to the Langdon table, what is characteristic of the auditory system in early tetrapods?
Inner ear sensitive to sound vibrations
-stapes involved in palatal, spiracular manipulations
(Spiracle=primitive opening into inner ear)
According to the Langdon table, what is characteristic of the auditory system in early therapsids?
Articular, quadrate, and stapes bones involved in conduction
According to the Langdon table, what is characteristic of the auditory system in the primitive mammals?
Dentary-squamosal joint established
Articular and quadrate bones specialized for transmitting vibrations
What is the transition from the quadrate-articular jointed jaw to a dentary-squamosal joint and what happens to the quadrate and articular bone?
Quadrate-articular–> quadrate-articular + dentary-squamosal–> dentary-squamosal
Quadrate and articular bones become reduced and eventually evolve into the incus and malleus
According to the Langdon table, what is characteristic of the auditory system in the advanced mammals?
- quadrate becomes incus**
- articular becomes malleus **
- angular becomes tympanic bone**
- middle ear sealed off behind tympanic membrane
- development of pinna (outer ear feature)
- sound localization
- sensitivity to high frequency
**=bolded on slide
What is another name for the tympanic bulla (bone)?
Auditory bulla
Where is the tympanic bulla found and what is it formed by?
Feature of squamosal bone; formed by tympanic part of temporal bone that houses the tympanic ring (bone)(angular)
In primates, what is the auditory bulla formed by?
Petrosal bone (Petrous part of temporal bone)
What ear ossicles develop from arch 1?
Malleus and incus
What ear ossicle develops form arch 2?
Stapes
Where is the tympanic/ectotympanic ring (angular) found in mammals and specifically in primates?
Position varies among mammals
In primates, may be within or outside the auditory bulla
Where does the tympanic/ectotympanic ring (angular) lie in lemurs?
Within auditory bulla cavity
Where does the tympanic/ectotympanic ring (angular) lie in lorises?
Attached to inside wall of bulla cavity
Where does the tympanic/ectotympanic ring (angular) lie in new world platyrrhines?
Attached outside wall of bulla
Where does the tympanic/ectotympanic ring (angular) lie in old wold catarrhines and tarsiers?
It is attached to outside wall of bulla but forms a bony ring (auditory tube=external auditory meatus)
What do the dryolestes, an early Jurassic mammal, show in their cochlea
Shows beginnings of modern therian mammal inner ear anatomy
According to the Langdon table, what is characteristic of the auditory system in humans?
- Specialized for hearing frequencies of human voice
- specializations for pitch, volume, direction, and language discrimination
- Broca’s area
- wernicke’s area
Where is the membranous labyrinth located?
In the petrous part of temporal bone
What is the pathway for the auditory system?
Primary auditory cortex–>wernickes area–> Broca’s area–> motor area
What enters through the internal acoustic meatus?
Vestibulaocochlear nerve and facial nerve
What is the function of the external ear?
Captures and funnels acoustic signals through the tympanic membrane to the middle ear
What does the middle ear contain and what is the function?
Contains a complex of small bones that then transmit sound vibrations to the inner ear where the organs of hearing and equilibrium are found
What is typically found in the inner ear?
Organs of hearing and equilibrium is found
Where is the middle ear found?
Found within the petrous part of temporal bone behind the tympanic membrane (ear drum)
What is the middle ear also known as? What does this connect to?
Tympanic cavity
Connects to nasopharynx via pharyngotympanic tube (Eustacian tube)
What lines the middle ear?
Mucus membrane
What 4 things are found in the middle ear?
Auditory ossicles
Stapedius and tensor tympani muscles
Chorda tympani nerve
Tympanic plexus of nerves
In what order do the tympanic memrbane, stapes, oval window, malleus, and incus interact?
Tympanic membrane, malleus, incus, stapes, oval window
What is the roof of the middle ear made up of? What bone is this a part of?
Tegmental wall
Temporal bone
Known as tegmen tympani
What is the flow of the middle ear made of?
Jugular wall
What is the lateral wall of the middle ear made of?
Membranous wall
Tympanic membrane
What is the medial wall of the middle ear and does this consist of?
Labyrinthine wall (cochlea, oval and round windows)
What is the anterior wall of the middle ear made of?
Carotid wall (internal carotid)
What is the posterior wall of the middle ear made of?
Mastoid wall (opening to mastoid antrum)
What are the auditory ossicles in general?
A mobile “chain” of tiny bones that articular with each other and transmit sound vibrations
What does the auditory ossicles span from?
The tympanic membrane (external) to oval window (internal)
What covers the auditory ossicles?
Mucus membrane but no periosteum
What moves the stapes?
Stapedius muscle
What muscle inserts on the malleus?
Tensor tympani
What does the internal ear contain?
Vestibulocochlear organ
Where is the internal ear located? What cranial nerve innervates this?
Buried deep within petrous part of temporal bone within otic capsule (hardest part of this bone)
Receives vestibulocochlear n (CN VIII) via internal acoustic meatus
What is the cochlea?
Shell shaped part of bony labyrinth containing cochlear duct, concerned with hearing
What is the vestibule?
Small oval chamber containing utricle and saccules, vestibular labyrinth for balance
What are the semicircular canal for and what does this communicate with?
Communicate with vestibule and used for balance
What is the internal acoustic meatus?
Narrow canal within petrous part of temporal bone that transmits the facial nerve, vestibulocochlear nerve and blood vessels though inner ear
Where is the endolymph of the ear found? What are the boundarys of this area?
In the scala media betwee the vestibular membrane and basilar memrbane
What all is found in the scala media?
Area between vestibular membrane and basilar membrane
Includes the endolymph, tectorial membrane, hair cells and sterocilia
Where is the perilymph found?
In the scala vestibuli and scala tympani which is on both sides of the scala media (endolymph)
Where do the low frequency sound waves exit the inner ear?
Via the round window
What is equilibrium?
A special sense that has to do with our sense of movement and where our body (particularly position of the head) is in space
How are the 3 semicircular canals oriented?
Superior
Posterior
Horizontal
What do the semicircular canals detect? What do they enclose?
Linear and rotational acceleration of the head.
They enclose specially shaped membrane called membranous labyrinth
What is characteristic of the endolymph in the vestibular apparatus?
Potassium rich fluid, it is inside the membranous labyrinth (continuous with cochlea)
What are ampullae in the vestibular apparatus?
Swellings at the base of semicircular canal
What is the crista ampullaris?
Sensory organ of angular acceleration and deceleration in each ampulla (3 pairs of them)
What is the cupula in the vestibular apparatus?
Gelatinous components of the crista ampullaris in ampullae
What is the utricle?
Otoliths organ within macula that is oriented horizontally–sense linear acceleration
What is the sacculus?
Otoliths organ within macula that is oriented vertically–sense linear acceleration
What lines the membranes of the inside of the vestibular organ?
Hair cells with stereocilia
What are the apical ends of the stereocilia in the vestibular apparatus bathed in?
Endolymph
What are the otoliths that are associated with otoliths organs?
Calcium carbonate crystals that sense gravity and linear accelerations
Which semicircular canal would detect a change when moving your head “yes”?
Anterior/superior
Which semicircular canal would detect a change when moving your head “no”?
Lateral/horizontal
Which semicircular canal would detect a change when tilting head?
Posterior ducts
