Describe the ear and it's mechanism
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Ear :
The human ear is called stato-acoustic
organ and it has two functions - hearing and body equilibrium. Anatomically the ear is made up of three parts : theexternal ear, middle ear and inner ear.
The external ear consists of ear pinna,
auditory canal and tympanic membrane. In humans, the ear pinna is an immovable part, supported by elastic cartilage structure. It leads into an auditory canal. The pinna collects and sends the sound waves into the auditory canal. The auditory canal ends at the ear drum. It
transfers the sound waves to the ear drum. There are very fine hair and wax secreting sebaceous glands in the skin of pinna and auditory canal. The tympanic membrane is a delicate, membranous structure which transmits the sound waves to the middle ear. It is formed of connective tissues covered with skin on the outside and mucous membrane on
the inside. The middle ear consists of chain of three ear ossicles called Malleus (hammer), Incus (anvil) and Stapes (stirrup-the smallest bone). On receiving the vibrations from the tympanic membrane, the ear ossicles amplify the vibrations and transfer these to the cochlea. A short eustachian tube connects the middle ear to the pharynx. It equalises air pressure on both sides of the ear drum. The internal ear consists of the labyrinth and vestibular apparatus. The labyrinth consists of bony labyrinth and membranous labyrinth. These are filled with perilymphcalled tectorial membrane. This organ acts as a transducer, converting sound vibrations into nerve impulses.
Inner Ear and the mechanism of balance :
Besides the cochlea, the inner ear also has the vestibular apparatus which is composed of three semi-circular canals and the utriculo saccular region with the otolith organ. All three semi-circular canals lie in different planes at right angle to each other. These canals are filled with endolymph. The base of each of the canal has an ampulla in which there is a
sensory spot called crista. The cristae help in maintaining equilibrium. The vestibule has two sensory spots-macula of saccule and utricle the macula consist of hair cells and supporting cells. Tips of the hair and cilium project into a thick gelataneous sheath otolithic membrane. Within this membrane minute particle otoliths or otoconia are secreted. These are made of CaCO3 and protein. The macula and crista are the receptors sensitive to the position of the head with respect to gravity. The three semicircular canals are arranged such away that the movement in any plane can be detected
by these cells and the balance and posture of the body is maintained. Receptors for dynamic balance lie in the cristae of ampullae while forstatic/linear balance these are in the maculae of utriculus and sacculus.
Mechanism of Hearing :
Pinna of the ear receives the sound waves and directs them to eardrum. Eardrum vibrates and these vibrations are amplified and transmitted through the ear ossicles to the endolymph inside cochlea. This generates, wave in the endolymph. These waves induce ripples in the basilar membrane. These movements in the basilar membrane cause the hair cells to press against tectorial membrane. This generates nerve impulse in the afferent neurons. Impulse is sent to the brain via the -auditory nerve. Auditory cortex of the brain decodes the sound.
EAR:-
The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and the ear canal. ... The middle ear includes the tympanic cavity and the three ossicles.
MECHANISM:-
The middle ear includes the tympanic cavity and the three ossicles.The mechanism of hearing. Sound waves enter the outer ear and travel through the external auditory canal until they reach the tympanic membrane, causing the membrane and the attached chain of auditory ossicles to vibrate.