1. The Ear, Hearing and Balance
Exercise 17: Activities 9, 11, 12, 13
Page

2. Objectives: Distinguish the three main divisions of the ear
Identify the primary structures of the ear on models
Understand the physiology of the ear and how it perceives sound and senses equilibrium
Demonstrate some clinical screening tests for hearing and equilibrium
Using the microscope, analyze the microscopic structure of the cochlea

3. vestibule (utricle, saccule, maculae, otoliths), vestibular nerve
semicircular canals (ampulla, cupula, crista ampullaris), vestibular nerve
microscopic anatomy of the cochlea (fig , scala vestibuli, vestibular membrane, cochlear duct, spiral organ (of Corti), tectorial membrane, hair cells, basilar membrane, scala tympani, spiral ganglion of cochlear nerve, cochlear nerve)
ceruminous glands
acuity
Weber test
Rinne test
Romberg test
balance test
nystagmus
Terms to know:
External Ear: pinna/auricle, external auditory meatus, tympanic membrane
Middle Ear: auditory ossicles: malleus, incus, stapes, oval window, pharyngotympanic (auditory) tube, round window
Inner Ear: bony labyrinth, membranous labyrinth, perilymph, endolymph
cochlea (scala vestibuli, cochlear duct, spiral organ (of Corti), scala tympani, basilar membrane, tectorial membrane, vestibular membrane), cochlear nerve

4. 9: Identifying Structures of the Ear
Outer and middle ear for hearing only, inner ear for hearing and equilibrium
Outer ear
Auricle or pinna
External acoustic meatus
Ceruminous glands secrete earwax
Tympanic membrane (eardrum) vibrates to transmit sound waves from outer to middle ear

6. 9: Identifying Structures of the Ear
Middle ear (tympanic cavity) is an air filled chamber in temporal bone
Contains auditory ossicles: malleus, incus, and stapes that transmit vibration to oval window
Pharyngotympanic (auditory) tube connects middle ear to nasopharynx
Used to equalize air pressure by “popping” your ears

10. 9: Identifying Structures of the Ear
Inner ear (osseous or bony labyrinth) is filled with perilymph
Contains membranous labyrinth filled with endolymph
3 subdivisions
Cochlea
Vestibule
Semicircular canals

12. 11: Examining the Microscopic Structure of the Cochlea
Stapes “footplate” vibrates oval window, which connects to scala vestibuli full of perilymph
Vibrations travel through the vestibular membrane to the endolymph filled 1.5 inch long cochlear duct (scala media) below
Spiral organ (of Corti) contains “hair cells” (stereocilia) for hearing reception imbedded in tectorial membrane which stimulate the vestibulocochlear (VIII) nerve
High frequency sound waves resonate close to the oval window while low frequency sound waves peak closer to the apex of the cochlea
Vibrations travel through basilar membrane below to the lower chamber, the scala tympani and dampen out on the “round window”

22. 12: Conducting Laboratory Test for Hearing
Acuity test-distance
Sound localization
Weber Test is used to determine conductive and sensorineural deafness
Rinne Test for comparing bone- and air-conduction hearing

23. Anatomy of Equilibrium Apparatus and Mechanisms of Equilibrium
Vestibule contains the saclike utricle and saccule
Semicircular canals contain the membranous semicircular ducts
Both:
Are suspended in perilymph
Are filled with endolymph
Contain receptor “hair cells” that are activated by disturbance of cilia and stimulate the vestibulocochlear (VIII) nerve

24. Semicircular Canals ½ inch circumference
Oriented in the three planes of space
Enlarged ampulla at the base of each contains a tuft of receptor hair cells referred to as the crista ampullaris topped with a gelatinous “ampullary cupula”
Perceive dynamic equilibrium in response to changes in angular motion
As cupula is moved by flow of endolymph, hair cells cilia are stimulated, which in turn stimulated the vestibular portion of the vestibulocochlear (VIII) nerve

28. Vestibule
Utricle and saccule membranous sacs contain maculae, static equilibrium receptors that respond to gravity and linear changes in speed
Maculae “hair cell” cilia are covered in otolith membrane containing calcium carbonate otoliths
Otolith inertia bends cilia on hair cells, which stimulates the vestibular portion of the vestibulocochlear (VIII) nerve

30. 13: Conducting Laboratory Test on Equilibrium
Balance Test
Nystagmus is the involuntary rolling of the eyes after rotation
Romberg Test to assess equilibrium and posture

31. For Review
Complete pages #20-32 All Mastering A&P assignments (8-11) are due on Saturday at 9:59 p.m.