The Ear

Anatomy of the Ear External Ear Auricle or pinnae surrounds the ear Helix Lobule

Anatomy of the Ear External acoustic meatus Ceruminous glands produce wax Hair Sebaceous glands Tympanic membrane Separates the outer ear from the middle ear Vibrates at the same frequency as the sound wave

Ear Figure 17.20

Middle ear- tympanic cavity Auditory ossicles – lever system that transmits the sound wave to the inner ear Malleus (hammer) Incus (anvil) Stapes (stirrup) Oval window – transmits the coming sound to the inner ear

Middle ear- tympanic cavity Round window – secondary tympanic membrane Auditory, Eustachian or Pharyngotympanic Tube – connects the middle ear with the nasopharynx Otites media – inflammation of the middle ear. Myringotomy – lancing of the eardrum

Inner Ear

Inner ear Bony or osseous labyrinth surrounds and protects membranous labyrinth Perilymph – aqueous fluid that fills the bony labyrinth Vestibule – involved in static equilibrium Semicircular canals – involved in dinamic equilibrium Lateral, anterior, posterior Cochlea – responsible for hearing

Inner ear Membranous Labyrinth Endolymph – viscous fluid that fills the ducts Cochlear ducts – located in the scala media Semicircular ducts – located in the semicircular canals Vestibule – located inside of the vestibule canal

Inner Ear

Microscopic anatomy of Organ of Corti Organ of Corti – for hearing Basilar membrane – forms the floor of the cochlear duct and supports the Organ of Corti Tectorial membrane – overlies the Organ of Corti. It’s gel-like and is in contact with the stereocilia of the hair cell Vestibular membrane – separates the scala vestibular from the scala media

Microscopic anatomy of Organ of Corti Scala vestibuli – filled with perilymph Scala tympani – filled with perilymph Scala media – filled with endolymph

Tests of Hearing Sound localization Frequency range Frequency is perceived a pitch. The higher the frequency the higher the pitch

Tests of Hearing Weber’s Test – determines: Sensorial deafness (Presbicusis)- caused by damage of the neural structures Conduction deafness- cased by anything that stops the sound conduction to the inner ear Rinne test Compares bone and air conduction hearing

Tests of Hearing Audiometry Measures frequency in hertz Measures amplitude in decibels. Amplitude is perceived as intensity or loudness of the sound

Microscopic anatomy of Equilibrium Apparatus Vestibular Apparatus Divided into utricle and saccule Macula Hair cells Otolithic membrane

Inner Ear Figure 17.23a, b, & d

Vestibular apparatus Monitors static equilibrium Ups and downs Movement of the head when the body is static Ups and downs Straight line changes Posture

Microscopic anatomy of Equilibrium Apparatus Semicircular canals and ducts Anterior, posterior and lateral Ampulla Hair cells Cupula

Inner Ear Figure 17.23a, b, & d

Semicircular canals and ducts Monitor dynamic equilibrium Perception of the rotational orientation of the head when the body is moving Boat riding

Tests on equilibrium Balance test Walk in straight line placing one foot directly in front of the other Barany test Evaluates the semicircular canals Rotates the person sitting in a rotating chair. Stop the rotation and observe if the person has nystagmus and vertigo Nystagmus is normal after rotation only Vertigo – dizziness and rotational movement when the person is static

Tests on equilibrium Romberg’s test Determines the integrity of the dorsal white column of the spinal cord Observes swaying movements when the person is standing erect and staring straight ahead Role of vision on equilibrium