Function of Mammalian Ear - Fundametnals of Biology - Lecture Slides, Slides of Biology

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Function of Mammalian

Ear

enable mammal to hear so that they can

escape from danger

detect changes in position during movement

Structure and Functions of Different

Parts of Ear

 ear is divided into three parts: outer ear, middle ear and

inner ear

Outer Ear

 outer ear includes pinna and an auditory canal outer ear

middle ear inner ear

auditory canal

 lined with hairs and wax-secreting cells to prevent entry of dust or small insects

 a membrane present at the end of auditory canal and it is called eardrum (typanum)

 eardrum serve as a device to convert sound waves into vibrations as when sound waves strike it, they are translated into mechanical waves

eardrum

auditory canal

Middle Ear

 air-filled cavity

behind eardrum

 contains three small

bones, ear ossicles: outer hammer(malleus), middle anvil(incus) and inner stirrup(stapes)

eardrum

 round window is another opening in the middle ear which allows

the exit of pressure caused by ear ossicles pressing on oval window

 middle ear is connected to pharynx by a passage called Eustachian

tube to equalize pressure on both sides of eardrum

 ear ossicles also amplify vibrations before reaching

oval window

Inner Ear

 bony cavity in skull and filled with fluid called perilymph

 inside this bony cavity is a group of membrane-bound structures

which contain endolymph and receptors including cochlea and three semicircular canals

many sensory hair cells present on the bottom membranes

endolymph is enclosed in the middle canal while canals on either

side of middle canal contain perilymph

 semicircular canal three semicircular canals are involved in detecting movement of head

both cochlea and semicircular canals have nerve fibres running to brain

these nerve fibres form auditory nerve

semicircular canals

atmospheric pressure

^ pressure inside middle ear

eardrum bulges inwards (you feel pain)

When you are landing…

eardrum returns to normal position

Solution: Yawning or Swallowing During swallowing, Eustachian tube is opened to let more air from

mouth enter middle ear to equalize pressure on both sides of eardrum

eardrum returns to normal position

Solution: Yawning or Swallowing During swallowing, Eustachian tube is opened to let air in middle ear to pass out through the Eustachian tube

Did you have to move your head in order to locate the sound source? Ans: The answer is supposed to be yes as sound waves travel in air in all directions.

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Detecting Movement of Head

 semicircular canals in inner ear detect movement of the head

 three fluid-filled semicircular canals are situated at an angle of 90o

to each other

 each canal is sensitive to movement in different plane

 at the base of each

canal is a swollen part called ampulla which contains sensory cells with protruding hairs embedded in a gelatinous structure