ANATOMY OF EAR.pptx

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

5. EXTERNAL EAR AURICLE EXTERNAL AUDITORYMEATUS TYMPANIC MEMBRANE

6. 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

7. 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)

8. 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

9. Middle ear

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

11. 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

12. 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

13. 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

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

15. 2) INCUS Anvil shaped Present between malleus and stapes

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

17. 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.

18. INNER EAR

19. 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

20. 1. BONY LABYRINTH Series of hollow channel. Filled with perilymph Consists of vestibul e 3 semicircular canal Spirally coiled cochlea

21. 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

22. 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

23. 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

24. COCHLEA Spiral shaped resembling snail’s shell wounded 2 3/4 th 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

25. SCALA VESTIBULI Communicates with vestibuli Contains perilymph

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

27. 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.

28. 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

29. PHYSIOLOGY OF HEARING

30. 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

31. 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.