Lecture 42 4/25/24 Flashcards
What is hearing?
the collection, neural processing, and analysis of vibrations generated by an object some distance away
What is sound?
the vibrations of air molecules
What are the characteristics of sound frequency?
-measured in Hertz/cycles per second
-tone of sound
-higher hertz means higher pitch
What are the characteristics of sound amplitude?
-measured in decibels
-loudness of sound
-higher decibels means louder sound
What are the characteristics of the pinnae?
-cartilage core with typical skin
-inner surface has less hair and more glands
What are the characteristics of the external acoustic meatus?
-vertical and horizontal portions
-cartilage lined by sparsely-haired skin
-sebaceous and ceruminous glands present
What are the characteristics of ear wax?
-composed of sebum and cerumen
-keeps tympanic membrane moist and flexible
-protects the ear canal
–antimicrobial
–water repellent
-removes debris
What is the function of the external ear?
collect and direct sound waves to the tympanic membrane
How does otitis externa differ from pinnal dermatitis?
-otitis externa is inflammation of external ear canal
-pinnal dermatitis is inflammation of the skin on the pinna
What are the characteristics of otitis externa in dogs?
-common, especially in long-eared breeds
-can be bacterial, fungal, or parasitic in origin
-can decrease ability to hear
-predisposes dogs to neoplasia
What is the main cause of otitis externa in cats?
ear mites
What is conduction deafness?
when the brain aspect of hearing works, but sound cannot be conducted
How can conduction deafness occur at the level of the external ear canal?
-ear wax that occludes external canal
-swelling and debris that occludes external canal
-tumor that occludes external canal
What are the characteristics of the tympanic membrane?
-separates external ear and middle ear
-in contact with bones of the middle ear
What are the bones of the middle ear?
-malleus
-incus
-stapes
What are the three layers of the tympanic membrane?
-outer cuticular layer (epithelial)
-middle fibrous connective tissue layer
-inner mucus layer (epithelial)
How does the tympanic membrane function in hearing?
transforms the energy of sound pressure wave into physical vibration of the auditory ossicles