耳鼻喉科教学课件：physiology of hearingand hearing loss

1、physiology of hearing and hearing loss anatomy of the ear（external ear,middle ear,inner ear） auricle external auditory canal tympanic membrane ossicular chain middle ear ltympanic cavity lpharyngotympanic tube lthe tympanic antrum lmastoid process tympanic cavity . cavity containing air， between the

2、 tympanic membrane and the inner wall. 1-2 milliliter pharyngotympanic tube lCommunicates middle ear and nasopharynx lTwo openings: pharyngeal opening of auditory ,tympanic opening of auditory tube Function： adjust gas pressure of tympanic cavity， maintain a balance of pressure inside and outside of

3、 tympanic membrane The middle ear cavity pressure is equal to atmospheric pressure mastoid cells,tympanic antrum There are many small gas cavity in normal mastoid bone, called the mastoid cells。 According to the degree of gasification, divided into four types。 pneumatic type sclerotic type diploetic

4、 type mixed type the maximum mastoid cells, Located in the upper part , called the tympanic antrum. tympanic antrum and the tympanic cavity are interlinked, is an important symbol of the operation. tympanic membrane lmanubrium of malleus lshort process of malleus lumbo lcone of light lMost of tympan

5、ic membrane embedded within the tympanic sulcus by fibrous cartilage ring,Known as the pars tensa. lThe upper tympanic membrane is directly attached to temporal bone scales, more relaxation,Known as the pars flaccida. Effective vibration area of tympanic membrane/The stirrup bone plate area =17 time

6、s. Sound pressure increases 17 times ossicular chain: malleus incus ,stapes Function of ossicular chain:As a lever system,Will transmit the sound waves from the tympanic membrane to the inner ear. how does the middle ear maximize the transfer of sound stimuli to the cochlea? l Length of Hammer shank

7、/Length of long limb of incus=1.3times. lSound pressure increase 1.3 times 171.3=22.1，amount to 27dB,Combined with the leverage of arc tympanic membrane，The whole pressure boost of middle ear is about 30 dB 30 dB the pathyway of sound conduction l Air conduction :transmission of sound to the inner e

8、ar via the ear canal and middle ear.the main route of transmission l Bone conduction: transmission of sound to the inner ear via skull bone The generation of auditory Hearing Loss Classification of hearing loss 1、Conductive hearing loss: is due to any condition that interferes with the transmission

9、of sound through the external and middle to the inner ear. 2、sensorineural hearing loss： the damage lies in the inner ear, the auditory nerve, or both. 3、central hearing loss： the damage is situated in the central nervous system at some point from the auditory nuclei to the cortex. 4、 functional hearing loss ：there is no detectable organic damage to the auditory pathways, but some underlying psychological or emotional problem is at fault. 5、mixed hearing loss： both c