Ch 10 PNS, Part 4 (Hearing)Learning Objectives1. Be able to identify the structures of the ear (all)2. Discuss the bones of the middle ear3. Explain how we hear4. Explain the mechanisms of balance & equilibrium in

the ear

Lend me your ear.

CSI: Can You Spot the Ear?

• http://video.google.com/videoplay?docid=-7933116988114927395&total=36&start=10&num=10&so=0&type=search&plindex=9

More info please >

Vacanti Mouse

• It might look like the work of a mad scientist but the Vacanti mouse with

what appears to be a human ear growing on its back is the real deal. You won't find this mouse at the circus; it was created at the University of Massachusetts in 1997. Dr. Charles Vacanti developed the mouse by putting a mold resembling the shape of a human ear onto its back.

• Dr. Vacanti is helping researchers fine tune a technology that will let them re-grow ears and noses for people. It was a plastic surgeon who suggested growing ears on mice after seeing kids who were born with out ears or who'd had them torn off in accidents.

• The 'ear' mold was made from special fibers that are biodegradable, much like dissolving stitches that doctors often use. Before the mold is implanted into the back of a hairless mouse, it is covered with cow cartilage cells. Blood from the mouse helps the cartilage cells grow and eventually replace the fibers. Researchers say that the rodent could have the ear removed and still remain alive and healthy.

Practice Activity: How Well Do You Know The Parts of the Ear?

• Answer question #10, Page 211 in your workbook now.

Hearing and Balance Pgs 210-211

• The three parts of the ear are the ______, ______, and ________ ear

• The outer and middle ear are involved with _______

• The inner ear functions in both hearing and ________

• Receptors for hearing and balance: – Respond to separate stimuli– Are activated independently

Outer, Middle and Inner EarLabel or bracket the three regions of the ear: outer, middle and inner on your diagram.

Outer Ear

• The auricle or ______ is composed of:– The helix (rim)– The lobule (earlobe)

• External auditory canal– Short, curved tube filled with ceruminous or ____

glands

• Tympanic membrane or ________– Thin connective tissue membrane that vibrates in

response to sound– Transfers sound energy to the middle ear ossicles – Boundary between outer and middle ears

pinna

wax

eardrum

Middle Ear

• A small air-filled mucosa-lined ______ – Flanked laterally by the ________– Flanked medially by the oval and round

windows

• Pharyngotympanic tube – connects the middle ear to the nasopharynx– _______ ________ in the middle ear cavity

with the external air pressure

cavity

eardrum

Equalizes pressure

Middle Ear

Bones of the Middle Ear

• The tympanic cavity contains three small bones: the ______,______, and ______.

• Transmit vibratory motion of the eardrum to the oval window

malleus incus stapes

Porpoise inner ear bones

These bones are formally named the "malleus", the "incus", and the "stapes", but they are more commonly known as the "hammer", the "anvil" and the "stirrup".

Inner Ear

• ______ labyrinth– Tortuous channels worming their way through the

temporal bone– Contains the _________, the __________, and the

_________________– Filled with fluid called _________

• __________ labyrinth– Series of membranous sacs within the bony labyrinth– Filled with a potassium-rich fluid

Bony

perilymph

Membranous

vestibule cochlea

semicircular canals

Vestibule

• The central egg-shaped cavity of the bony labyrinth

• Suspended in its perilymph are two sacs: the saccule and utricle

• The saccule extends into the cochlea• The utricle extends into the semicircular canals• These sacs:

– House equilibrium receptors called maculae– Respond to gravity and changes in the position of the

head

Semicircular Canals

• Three canals that each define two-thirds of a circle and lie in the three planes of space

• Membranous semicircular ducts line each canal and communicate with the utricle

• The ampulla is the swollen end of each canal and it houses equilibrium receptors in a region called the crista ampullaris

• These receptors respond to angular movements of the head

Cochlea

• A spiral, conical, bony chamber that:– Extends from the anterior vestibule– Coils around a bony pillar called the modiolus– Contains the cochlear duct, which ends at the

cochlear apex– Contains the organ of Corti (hearing receptor)

Internal Ear Anatomy Instructions: Label the malleus, incus, stapes, eardrum, cochlea, vestibule, and

semicircular canals on your practice diagram now.

How Do We Hear?

• Sound vibrations beat against the eardrum

• The eardrum pushes against the ossicles, which presses fluid in the inner ear against the oval and round windows– This movement sets up shearing forces that

pull on hair cells– Moving hair cells stimulates the cochlear

nerve that sends impulses to the brain

Hearing & Balance

• http://video.google.com/videoplay?docid=-4811948101588376689&q=balance+%2B+middle+ear&total=26&start=0&num=10&so=0&type=search&plindex=0

Balance & Equilibrium

• Vestibular apparatus – __________

in the semicircular canals and vestibule– Maintains our _________________ in space– Vestibular receptors monitor static equilibrium– Semicircular canal receptors monitor dynamic

equilibrium

equilibrium receptors

orientation and balance

Balance & Equilibrium continued

• Maculae are the sensory receptors for static equilibrium– Contain supporting cells and hair cells

• Otolithic membrane is a jellylike mass studded with tiny CaCO3 stones called _________

• Utricular hairs respond to ________movement• Saccular hairs respond to _______ movement

otoliths

horizontal

vertical