Please scroll down to get to the study materials.
there is well-developed organ of hearing in the man called ears, Each ear is stimulated by sound vibration or sound wave the ear consists of three different parts:-
1 External ear
2 middle ear or tympanic cavity
3 internal ear
the external ear consists of two different part auricles and external acoustic meatus.
the auricle is the external flap expanded part of the ear which is also pinaa. it is projected from the side of the head and made up fribro cartilage covers by hair skin pinna, consists of large number of grooves and ridges of which ,the ,most prominanet outermost ridge is called the helix ,the lower part of pinna consists of a soft part called the lobule made of fibrous and adipose tissues with blood vessels.
the external acoustic meatus is small tube almost Shaped or slightly curve structure which is also known as an auditory canal or ear cannel it extends from the auricle to the ear drum (tympanic membrane).
it is about 2.5 cm in length this canal is found inside the temporal bone. it is tied with has skin .the skin is provided with numerous sebaceous gland and modified sweat gland called ceruminous gland. the later secreted a waxy material called the cerumen the curved structure of meatus hair and the waxy substance prevent the foreign particle from reaching the ear drum.
the ear dum or tympanic membrane separates, the external acoustic meatus from the middle ear the ear drum consists of three layers the outer layer of the hairless skin .the middle layer of fibrous tissues and the inner mucous membrane lining the mucous membrane lining of the tympanic membrane is consists of membrane of middle ear or said to be middle ear.
middle ear (tympanic cavity )
the middle ear is the club shaped lie in the temporal bone lined with epithelium the cavity is filled with air at atmospheric pressure the cavity is provided with several openings:-
1 opening of external auditory meatus
2 two opening into the internal ear the oval window occluded by the stape and the round window covered by membrane
3 opening to the nasopharynx the Eustachian tube
the middle ear consists so f the three small bone called ear ossicles the malleus incus and stapes the three ossicles from a series of moveable with each other.
the malleus is hamber shaped bone its handles is articulated to the tympanic membrane .the head portion of the malleus form a movable synovial joint to the main body the incus .incus is an anvil-shaped bone the long process of the incus articulated to the stapes by all and socket joint the stapes, in turn, fits into fenestra ovalis.
the eEustachian canal is about 4 cam in length. it helps to maintain the atmospheric pressure on both the sides of the tympanic membrane .the eustachian tube is also known as the pharyngotympanic tube ,when the pressure on both side the tympanic membrane is equal it enables the membrane to vibrate due to the stick of sounds waves.
te internal ear is mainly concerned with two function hearing and balancing. it is also known as labyrinth due to its complicated structure. it consists of two main parts bony labyrinth and membranous labyrinth.
the bone labyrinth is a cavity in the temporal bone .it lodges the membrane labyrinth of the similar shaped there is space between the bony and membranous labrythin is filled with a watery fluid called perilymph .the boney labyrinth consist of three main part vestibule cochlea and semicircular canal.
the vestibule is middle peart of the bony labyrinth which is provided with oval and round windows the middle-end oval and round window they all end to middle end and open to the vistule through these windows.
the cochlea is snail-like structure (the words cochlea means snail). the broad ends of the cochlea are attached to the vestibule it narrow end is and its coils spiral towards the apex.
there is three tubular canals continues with the vestibule the semicircular canal are arranged in three different lanes of the space.
the membranous labyrinth is also similar to the bony labyrinth in shaped .it is also divided into three structure similar to the bony labyrinth vestibule cochlea and three semicircular canals .the vestibule consists of two different parts utricle and saccule the membranous labyrinth is filled up the hand , saccule is connected to the cochlea.
three semicircular canals of membraneous labyrinth are arranged in three different planes of the space .these semicircular canal of membranous labyrinth are arranged in three different plan of the space these semicircular canals are according to their position anterior-posterior and lateral anterior and posterior .semicircular canal are vertical in position originate commonly from crush one the lateral semicircular canal is horizontal in position .each semicircular canal opens into the utricle by both the end the anterior and posterior .semicircular canal are joined with each other before inro the utricles one end of each of the semicircular canal is enlarged to form an ampulla each ampulla is provided with a sensory spot called crista cristae resemble with macular in most of the aspects.
both the utricle and saccule are proviged with the small sensory spot called the macules. each macula is also provided with some hair cell and gelatinous membrane. the gelatineous membrane otoith membrane is provied with numerous otoisths i ,they are mine stone like structure of calcium carbonates.
the hearing is one of the main function of the ear, that detects sound waves or vibration in the air beside detection. it also judges the direction and loudness of the sound.
the pinna is specially built to concentrate the sound wave towards the auditory meatius. the sound waves vibrate the typanic membrane ,the vibration from the tympanic membrane are ten transmitted through the middle ear by ossicle to each of the membranes of the fenestra ovalis.
the ear also helps forming balancing the body the main parts of the ear involved in equilibrium are cristae and maculae, when position of the head is changed the perilymph and endolymph do not move with the same speed .initially due to their inertia when the head stops moving these fluid continues to flow and cause sweeping of sensory hairs of the cristae and maculae.
Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069
Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.
Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.
hearing is one of the main fuction of the ear that detects sound waves or vibration in the air beside detection it also judge the direction and loudness of the sound
the pinna is specially built to concentrate the sound wave towards the auditory meatius the sound waves vibrate the typanic membrane the vibration rom the typmanic membrane are ten transmitted through the middle ear by ossicle to each of the membrane of the fenetra ovalis