anatomy of ear in short

1. ANATOMY OF
EAR
By: Ms. Saili Gaude
Principal
Shivam College Of Nursing , Amirgadh

2. HUMAN EAR
◦ Ear is sensitive organ of human body
◦ Mainly concerned with detecting and transmitting and transducing sound
◦ Maintaining a sense of balance

3. STRUCTURE OF HUMAN EAR
◦ Divided into 3 parts
EXTERNAL EAR MIDDLE EAR INTERNAL EAR

4. EXTERNAL EAR

6. EXTERNAL EAR
AURICLE EXTERNAL AUDITORYMEATUS
TYMPANIC MEMBRANE

7. AURICLE
◦ Pinna
◦ Composed of thin plate of elastic cartilage covered by layer of skin
◦ Funnel like curves of auricle collects sound wave
◦ These are directed to the middle ear
◦ Deepest depression of pinna is called concha
◦ Concha consist of 2 small projections called:
◦ 1) Tragus
◦ 2) Antitragus

8. EXTERNAL AUDITORY MEATUS
◦ Slightly curved canal of about 2.5 cm
◦ Extends from floor of concha to the tympanic
membrane
◦ Meatus is lined with skin continuous with auricle
◦ Contains 2 glands- sebaceous and ceruminous
gland
◦ Ceruminous gland- modified sweat glands that
secretes cerumen (wax)

10. TYMPANIC MEMBRANE
◦ Oval bluish grey membranous structure located on medial part of auditory meatus
◦ Seperates external and middle ear
◦ Stretchable organ capable of vibrating
◦ Recives sound waves and amplifies into appropriate magnitude

11. MIDDLE EAR

12. MIDDLE EAR
◦ Small chamber between tympanic membrane and inner
ear.
◦ Consists of tympanic cavity and ear ossicles

13. TYMPANIC CAVITY
◦ Narrow irregular air filled space in temporal
bone
◦ Separated from external ear by tympanic
membrane and medially from inner ear by
bony wall
◦ 2 opening – oval window and round
window
◦ Anterior wall of tympanic cavity have
auditory tube called as the eustachian tube

14. EUSTACHIAN TUBE
◦ Eustachian tube leads downward from tympanic cavity to nasopharynx
◦ 4cm long
◦ Mucus membrane lining nasopharynx is continuous with membrane of tympanic cavity through
eustachian tube
◦ As a result , infection from nose and throat may spread to middle ear causing otitis media
◦ Main function of eustachian tube:
◦ - Maintain equal pressure on both side of tympanic membrane by permitting air to pass from
nasal cavity to middle

16. EAR OSSICLES
◦ Three ear ossicles from a chain of lever extending from tympanic membrane to inner ear
◦ Ear ossicles communicate the ear drum with internal ear through fenestra ovalis (oval window)
◦ The three ossicles are :
◦ 1) Malleus
◦ 2) Incus
◦ 3) Stapes

18. 1) MALLEUS
◦ Hammer shaped
◦ Handle in contact with tympanic membrane
◦ Head forms movable joint with incus

19. 2) INCUS
◦ Anvil shaped
◦ Present between malleus and stapes

20. 3) STAPES
◦ Stirrup shaped bone
◦ Head articulates with incus
◦ Foot plate fits into oval window
◦ Smallest bone of our body

21. OVAL WINDOW
◦ Also known as fenestra ovalis
◦ It is a connective tissue membrane located at the end of the middle ear and beginning of the
inner ear
◦ Sound waves causes vibration of the tympanic membrane and the ossicles transmit those
vibrations to the oval window which leads to movement of fluid within the cochlea and
activation of receptors for hearing.

22. INNER EAR

24. INNER EAR
◦ Also called labyrinth because of its intricate structure
of interconnecting chamber and passage
◦ Consist of 2 main structural part
◦ 1) Bony labyrinth
◦ 2) Membranous labyrinth

25. 1. BONY LABYRINTH
◦ Series of hollow channel.
◦ Filled with perilymph
◦ Consists of vestibule
◦ 3 semicircular canal
◦ Spirally coiled cochlea

26. 2. MEMBRANOUS LABYRINTH
◦ Surrounded by bony labyrinth
◦ Filled with endolymph
◦ Contains sensory receptors for hearing and equilibrium
◦ Membranous labyrinth consists of semi circular ducts as well as utricle, saccule and cochlear duct,
all filled with endolymph enclosed by bony labyrinth
◦ Also contains sensory receptors. These are cristae, ampullaris maculae and organ of corti
◦ Semi circular ducts are located within semicircular canal of bony labyrinth
◦ Perilymph is located in space between duct and bony wall of semicircular canal

27. VESTIBULE
◦ Expanded part nearest the middle ear
◦ Has 2 sacs : larger upper utriculus and smaller lower sacculus
◦ Utriculus and sacculus is connected by utriculosaccular duct
◦ The sensory spot (macula ) is present in both utricle and sacculus
◦ Macula consists of otolith membrane having otolith which is concerned with balancing of body

28. SEMICIRCULAR CANAL
◦ Associated with equilibrium or balancing not for hearing
◦ 3 semicircular canals arises from utriculus, anterior, posterior and lateral canal
◦ Anterior and posterior canals opens at one end to form common duct called crus commune. One
end of each semicircular canal is swollen to form ampulla

29. COCHLEA
◦ Spiral shaped resembling snail’s shell wounded 2 3/4th times
◦ Main organ of hearing
◦ Connected with cerebrum by vestibulo cochlear nerve
◦ Divided into 3 spiral fluid filled chamber
◦ 1. SCALA VESTIBULI
◦ 2. SCALA TYMPANI
◦ 3. SCALA MEDIA OR COCHLEAR DUCT

30. SCALA VESTIBULI
◦ Communicates with vestibuli
◦ Contains perilymph

31. SCALA TYMPANI
◦ Ends at round window of tympanic cavity
◦ Contains perilymph

32. SCALA MEDIA OR COCHLEAR DUCT
◦ Lies between scala vestibuli and scala tympani
◦ Contains endolymph
◦ Separated from scalvestibuli by vestibular membrane
◦ Separated from scala tympani by basilar membrane
◦ Basilar membrane have organ of corti formed from about 24000 receptor aurditory cells.

33. ORGAN OF CORTI
◦ Organ of hearing which is rested on basilar mebrane
◦ Organ of corti is present within scala media of cochlea that receive and conduct sound stimulus
◦ Organized structure consisiting of hair cells and supporting cells
◦ Hair cells are arranged in rows along the length
◦ The outer hair cells are arranged in 3 rows and inner hair cells are arranged in single row.
◦ Each outer and inner hair cell have sensory hair which are specialized microvilli

34. PHYSIOLOGY OF HEARING
Every sound
produces waves
Auricle Auditory canal
Tympanic
membrane
Auditory
ossicles
Oval window
Wave produces
perilymph
Move to
membranous
Labyrinth

35. Causes wave in
endolymph
Contracts the
waves
Stimulate the neuro
epithelial cells
Nerve impulse
passes to
vestibulocochlear
nerve
Trnasmitted to
cerebrum for
auditory perception

36. MECHANISM OF HEARING
◦ Sound waves are collected by the external ear up to some extent
◦ They pass through the external auditory meatus to the tympanic membrane which is caused to vibrate
◦ Vibrations are transmitted across the middle ear by the malleus, incus and to the stapes bones. The latter fits into the fenestra ovalis.
◦ From the perilymph the vibrations are transferred to the scala vestibuli of cochlea and than to scala media through Reissner’s membrane
◦ Subsequently the movements of endolymph and tectorial membrane stimulate the sensory hairs of the organ of corti
◦ The impulses thus received by the hair cells are carried to the brain through the auditory nerve where the sensation of hearing is felt.
◦ It is evident that the external and middle ears serve to transmit sound waves to the internal ear
◦ It is the internal ear that the transformation of the vibrations into nerve impulses for relay to the brain takes place
◦ From scala tympani the sound waves are transmitted to the tympanic or middle ear cavity the sound waves are transferred to the pharynx through,the
Eustachian tube

37. EQUILIBRIUM
◦ The semicircular canal,utricle and saccule of membranous labyrinth are the structures of equilibrium
◦ Whenever the human displaced the hair cells of the cristae and maculae are stimulated by the movement of the endolymph
◦ The stimulus is carried to the brain through the auditory nerve and change of the position is detected by the medulla oblongata of the
brain. After that, the brain sends impulses to the muscles to regain the normal conditions.