PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART B 8 Ears and Hearing

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ears Med Terms 1.Cochlea – snail 2.itis - inflammation 3.Labyrinth – maze 4.Lymph - fluid 5.Oss - bone 6.Oto – ear 7.Peri – covering 8.Semi - half 9.Tympan – drum 10.Vestibul - chamber

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear  The ear is divided into three areas  External (outer) ear  Middle ear (tympanic cavity)  Inner ear (bony labyrinth)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Ear  Houses two senses  Hearing  Equilibrium (balance)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The External Ear  Involved in hearing only  Structures of the external ear  Auricle (pinna)  Funnels sound waves  External acoustic meatus (auditory canal)  Narrow chamber in the temporal bone  Lined with skin and ceruminous (wax) glands  Ends at the tympanic membrane

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Why wax?  The actual wax that is observed is the coating of the inside of your ear in order to protect it from things entering the ear canal. Ear wax is produced by a gland that is inside your ear, to help keep away dirt, bugs, and even germs. When your ears are not cleaned for a long time, the wax eventually just dries up and falls out in tiny, flaky bundles that you don't even realize.  ~D.W.

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity)  Air-filled cavity within the temporal bone  Only involved in the sense of hearing

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity)  The opening from the auditory canal is covered by the tympanic membrane  Tympanic Membrane - vibrates in response to pressure changes  The auditory tube connects the middle ear with the throat  Allows for equalizing pressure during yawning or swallowing

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The auditory tube  If pressure outside is greater than inside, ears will “pop”  Chewing gum can help equalize pressure

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ear Infections (Otitis media)  Don’t close nostrils when blowing nose, can force debris into the ears causing infection of the middle ear (otitis media)  Frequent ear infections can receive “tubes” for drainage

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Bones of the Middle Ear (Tympanic Cavity)  Three bones (ossicles) span the cavity  Malleus (hammer)  Incus (anvil)  Stapes (stirrip)  Function  Vibrations from eardrum move the Malleus  Incus  Stapes  inner ear

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Inner Ear or Bony Labyrinth  Vibrations enter through the oval window from the Stapes  Vibrations move perilymph fluid in:  Semicircular canals  Sensing equilibrium  Vestibule  Connects semicircular canals to cochlea  Cochlea  Contains the hairs for hearing senses

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cochlea  Hair Cells

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A sense of hearing  Cell membrane protein channels open in response to changes in frequencies  Allow Ca +2 ions to flow into the cells  Triggers neurotransmitter release  Sends signal through vestibulocochlear nerve to the brain

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Hearing Figure 8.16a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Decibels (dB) - measure sound intensity  0 dB - least perceptible by humans  40 dB - whispering  dB - normal conversation  80 dB - heavy traffic  90 dB - above this can damage hearing receptors  120 dB - Rock concert  140 dB - Jet plane takeoff

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Partial or complete hearing loss  Eardrum can harden as a result of disease  Eardrum can tear or perforate due to disease or injury  Loud sounds, tumors, brain damage or drug use can damage nerve pathways

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Equilibrium  Equilibrium receptors of the inner ear are called the vestibular apparatus  Vestibular apparatus has two functional parts  Static equilibrium  Dynamic equilibrium

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Equilibrium Figure 8.14a–b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Static Equilibrium  Maculae—receptors in the vestibule  Report on the position of the head  Send information via the vestibular nerve

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the maculae  Hair cells are embedded in the otolithic membrane  Otoliths (tiny stones) float in a gel around the hair cells  Movements cause otoliths to bend the hair cells

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of Maculae Figure 8.13a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of Maculae Figure 8.13b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium  Crista ampullaris—receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers the hair cells

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium Figure 8.14c

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium  Action of angular head movements  The cupula stimulates the hair cells  An impulse is sent via the vestibular nerve to the cerebellum  The brain interprets the signals and “predicts” the consequences  Signals to the appropriate skeletal muscles and allows the cerebellum to maintain balance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Other Sensory Structures  Maintaining equilibrium is a combined effort:  Hair Cells  Receptors in your neck  Eyes

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Motion Sickness  Abnormal or irregular body movements that disturb the organs of equilibrium  Nausea, vomiting, dizziness or headache