EARS Flashcards
Separated from the middle ear by the tympanic membrane
ANATOMY OF THE EXTERNAL EAR
composed mainly of cartilage, except for the fat and subcutaneous tissue in the earlobe.
collects the sound waves and directs vibrations into the external auditory canal.
AURICLE
approximately 2 to 3 cm long The lateral third is an elastic cartilaginous and dense fibrous framework to which thin skin is attached. The medial two thirds is bone lined with thin skin.
ends at the tympanic membrane.
contains hair, sebaceous glands, and ceruminous glands, which secrete a brown, waxlike substance called cerumen (ear wax)
EXTERNAL AUDITORY CANAL
Approximately 80% of the tympanic membrane is composed of all three layers and is called the pars tensa. The remaining 20% lacks the middle layer and is called the pars flaccida.
TYMPANIC MEMBRANE
normally pearly gray and translucent
It consists of three layers of tissue: 1. an outer layer, continuous with the skin of the ear canal; 2. a fibrous middle layer; 3. an inner mucosal layer
TYMPANIC MEMBRANE
The sound pressure is magnified 22 times as a result of transmission from a larger area to a smaller one.
TYMPANIC MEMBRANE
Two small fenestrae (oval and round windows), located in the medial wall of the middle ear, separate the middle ear from the inner ear.
The footplate of the stapes sits in the oval window, secured by a fibrous annulus (ring-shaped structure). The footplate transmits sound to the inner ear.
OSSICLES
three smallest bones of the body
- malleus
- incus
- stapes
The round window, covered by a thin membrane, provides an exit for sound vibrations.
OSSICLES
housed deep within the temporal bone
ANATOMY OF THE INNER EAR
composed of the utricle, the saccule, the cochlear duct, the semicircular canals, and the organ of Corti, all of which are surrounded by a fluid called endolymph.
MEMBRANOUS LABYRINTH
The three semicircular canals— posterior, superior, and lateral, which lie at 90-degree angles to one another— contain sensory receptor organs that are arranged to detect rotational movement.
These receptor end organs are stimulated by changes in the rate or direction of a person’s movement.
The utricle and saccule are involved with linear movements.
MEMBRANOUS LABYRINTH
located on the basilar membrane that stretches from the base to the apex of the cochlea
ORGAN OF CORTI
Also referred to as the end organ for hearing, transforms mechanical energy into neural activity and separates sounds into different frequencies.
ORGAN OF CORTI
Sounds transmitted by air conduction travel over the air-filled external and middle ear through the vibration of the tympanic membrane and ossicles.
Sounds transmitted by bone conduction travel directly through bone to the inner ear, bypassing the tympanic membrane and ossicles.
HEARING
is maintained by cooperation of muscles and joints of the body (proprioceptive system), the eyes (visual system), and the labyrinth (vestibular system).
These areas send their information about equilibrium, or balance, to the brain (cerebellar system) for coordination and perception in the cerebral cortex.
BALANCE AND EQUILIBRIUM
When evaluating hearing, three characteristics are important: frequency, pitch, and intensity.
AUDIOMETRY
refers to the number of sound waves emanating from a source per second, measured as cycles per second, or Hertz.
The normal human ear perceives sounds ranging in frequency from 20 to 20,000 Hz. Frequencies from 500 to 2000 Hz are important in understanding everyday speech and are referred to as the speech range or speech frequencies.
Frequency
is the term used to describe frequency; a tone with 100 Hz is considered of low pitch, and a tone of 10,000 Hz is considered of high pitch.
Pitch
The unit for measuring loudness is the decibel (dB), the pressure exerted by sound. Hearing loss is measured in decibels—a logarithmic function of intensity that is not easily converted into a percentage.
(intensity of sound)
A tympanogram, or impedance audiometry, measures middle ear muscle reflex to sound stimulation and compliance of the tympanic membrane by changing the air pressure in a sealed ear canal.
Compliance is impaired with middle ear disease.
TYMPANOGRAM
MORE THAN 28 MILLION PEOPLE IN THE USA HAVE SOME TYPE OF HEARING IMPAIRMENT
MOST CAN BE HELPED W/ MEDICAL OR SURGICAL THERAPIES OR W/ A HEARING AID
BY THE YEAR 2050, ABOUT ONE (1) OUT OF EVERY FIVE (5) PEOPLE IN THE USA, OR ALMOST 58 MILLION PEOPLE, WILL BE AGE 55 OR GREATER
OF THIS POPULATION, ALMOST ONE-HALF CAN EXPECT A HEARING IMPAIRMENT
HEARING LOSS STATISTICS
