The Ear Flashcards
are complex sensory organs located on each side of the skull, mostly buried within each temporal bone.
The ears
The ear serves as a receptor organ for at least three special senses:
hearing, static equilibrium, and dynamic equilibrium.
The external (outer) ear is the ear division composed of the elements described in the following:
Auricle
External auditory meatus
Tympanic membrane
This external ear flap protects the auditory opening and directs sound waves toward it. It also fune-tions as a “radiator” in thermoregulation.
Auricle (pinna)
This tube-like passage carries airborne sound waves further into the ear apparatus; it is also called the ear canal.
External auditory meatus
Also called the eardrum, it covers the end of the external auditory meatus to form a boundary with the middle ear. It vibrates when struck by airborne sound waves, carrying the sound energy into the middle ear.
Tympanic membrane
Components of middle ear
Malleus
Incus
Stapes
Auditory tube
begins where the external ear ends, with the tympanic membrane.
MIDDLE EAR
The ___ is an air-filled cavity lined with mucous membrane.
middle ear
It is one of the three auditory ossicles in each ear.
Also called the hammer, it is a tiny, club-shaped bone attached to the eardrum. It vibrates when sound waves pass to it from the eardrum.
Malleus
Also called the anvil, this tiny bone forms a synovial joint with the malleus. The incus vibrates when it receives energy from the malleus.
Incus
Also called the stirrup because of its shape, this ossicle is joined to the incus, from which it receives vibra-tions. A flat portion of the stapes fits into the oval window, a passage into the inner ear.
Stapes
Because of the structural relationship of this chain of ossicles, sound waves are carried from the tympanic membrane to the ___ (i.e., from the external ear to the inner ear). Along the way, the vibrations are amplified for better reception.
oval window
This is a collapsible tube running between the middle ear and the pharynx. It allows internal air pressure to equalize with atmospheric air pressure so that high pressure on one side does not distort or muffle the eardrum.
Auditory (eustachian) tube
The ___ is the third division of the ear apparatus.
inner ear
The receptors for hearing and equilibrium are located here.
Inner ear
The inner ear is within a hollow area in the petrous portion of the ___ bone.
temporal
A maze-like bony labyrinth contains a similarly shaped but smaller membranous labyrinth.
The fuid inside the membranous labyrinth is called ____, and the fuid around the outside of the membranous labyrinth is called ____.
endolymph
perilymph
The bony labyrinth, and the membranous labyrinth inside it, is composed of the three main regions described in the following:
Cochlea
Vestibule
Semicircular canals
This is a long passage coiled like a snail.
A c.s. reveals that the passage is divided into three chambers by a Y-shaped partition.
The base of the Y is a projection of the bone called the ___.
The two branches are pieces of membrane called ____ and ____.
Cochlea
spiral lamina
the vestibular membrane and the basilar membrane
This is the central area of the inner ear. The ___ contains sac-like portions of the membranous labyrinth called the ____ and ___
Each has a patch of sensory hair cells called a ___
Vestibule
Utricle, saccule
macula
The macula’s hair cells are covered by a gelatinous coating embedded with hard, tiny crystals called ___.
otoliths
When the head is tilted, gravity pulls on the heavy otoliths and the hairs ___. This induces a receptor potential.
bend
Sensory information regarding the effects of gravity (static equilibrium) is transmitted to the brain through the ____, another branch of cranial nerve VIII.
vestibular nerve
These are three round passages, each on a different plane.
Semicircular canals
The semicircular canals have bubbles at their bases called ___
ampullae
Within each ampulla is a crest of tissue called the ____.
crista ampullaris
Each crista is a patch of sensory hair cells covered with a gelatinous mass (without otoliths) called the ___.
When the speed or direction of movement of the head changes, the inertia of the endolymph within the semicircular canals causes it to circulate.
As the endolymph circulates, it pushes the cupula and generates receptor potentials in the crista’s sensory cells.
The vestibular nerve carries the signal to the brain, where it is interpreted as kinetic (dynamic) equilibrium
cupula
