Exam #3 Ch 8 Auditory System; middle and outer ear

Outer ear

The pressure waves of speech impinge upon the outer ear and stimulate the ear drum

Pinna

external "flap" on the side of the head, often referred to as "the ear." flexible elastic cartilage, except for lobe. attached to cranium side by ligaments.

function of the pinna

help channel sound waves into the ear canal, particularly high-frequency sounds/protect entrance to external auditory meatus/detect sound source and direction.

External auditory meatus

channel leading from pinna to tympanic

External auditory meatus function

protects the more delicate parts of the ear from trauma and from the intrusion of foreign objects.

membrane(aka ear canal); enhance/boost high frequencies of sound/2.5 cm in length/Quarter-wave resonator

Cerumen

earwax, a waxy substance that protects the ear canal from dust, dirt, and bacteria

Cerumen function

Protects the ear/Lubricates the ear/Has antibacterial properties/Self-cleans

Cilia

hair-like structures that extend from the surface of cells

Cillia two main functions

to move fluid and particles, and to act as sensory antennas that detect mechanical or chemical stimuli

What connects the outer and middle ear

Tympanic membrane

Tympanic membrane is what

processes low/high frequencies; eardrum/vibrates

Tympanic membrane vibrates when

acoustic pressure waves impinge on it. part of malleus is embedded, vibration is transmitted to malleus and incus/stapes. extremely sensitive to tiny pressure variations. responds to a wide pressure/frequency range

Tympanic membrane is involved in the process of

transducing pressure waves to mechanical vibration

Middle ear

the pressure waves are converted to mechanical vibrations by a series of three small bones leading to the cochlea

Eustachian tube

front-most two-thirds of tube lies in cartilage canal/posterior one-third in a bony canal. The tube runs from the nasopharynx to the middle ear

Eustachian tube function

1st serves to keep middle ear space ventilated and drained by equalizing pressure, 2nd clear mucus from middle ear by draining mucus to pharynx, where it is swallowed

Ossicles (chain)

smallest bones in human body, connected to ™ on one side and then oval window on the other

Ossicles function

Bridge between tympanic membrane and the oval window of the cochlea and Sound vibration (outer ear) mechanical vibrations (ossicle chain)

Malleus

or hammer, has two major parts—the head and the handle (manubrium). The manubrium is embedded in TM, while the head extends into the epitympanic recess. The tip of the manubrium coincides with the umbo.

Malleus function

transmit sound vibrations from the eardrum to the incus

Incus

or anvil, is connected to malleus/stapes(stirrup) is attached to oval window. also about 8 mm in length. It has a rounded body from which two processes extend

Incus function

transmits sound vibrations from malleus to stapes. Relays vibrations, crucial link in auditory ossicle chain that amplifies and transmits sound from eardrum to inner ear

Stapes

has a body, with an anterior/posterior crus (leg) converging on it from either side. The oval-shaped footplate fits into the oval window of the inner ear and is held in place by a ligament.

This ossicular chain, is supported by

ligaments and forms the mechanical vibrating element of the auditory system

Stapes function

transmitting sound vibrations from incus (anvil) to oval window of the inner ear. This action pushes fluid inside the cochlea, which stimulates the hair cells that send signals to the brain, allowing us to hear

Impedance through liquid medium

approx 99% of sound pressure waves traveling through air medium are reflected back from a liquid medium. Liquid offers higher resistance, to sound pressure than gas (such as the air)

Impedance

a measure of resistance, determined by medium