Anatomy Flashcards
The auditory system is divided into what components?
Peripheral and central
The Peripheral Portion consists of:
-The outer ear
-The middle ear
-The inner ear
-The auditory nerve (VIII cranial nerve)
What does the central portion do?
it deals with the processing of auditory information as it is carried up to the brainstem & auditory cortex of the brain ( parietal lobe)
The outer ear consists of:
-The Auricle
-External Auditory Canal
What is another name for the Auricle?
Pinna
Tell me more about the Auricle:
-provided by cartilage, except the lobule
-covered with a layer of epithelial tissue
-Helix is marking the most distal border
-Tragus projects immediately in front of the ear canal
Point out the landmarks of the Auricle?
refer to slide 6
Tell me more about the External Auditory Canal (EAC):
-External Auditory Meatus (EAM)
-S-shaped
-its approximately 0.7 cm in diameter and 2.5 cm long
-there are two constrictions in the EAC, osseocartilaginous junction and the isthmus which is 0.5 cm from the tympanic membrane
What are the functions of the EAC?
-The auricle collects and conducts sound to the EAC
-The EAC amplifies the sound around 12 dBS by its resonance frequency
-protects the tympanic membrane from trauma, insects & FBs
-self cleaning property
-Malformation of pinna and EAC
-Otorrhea: ear discharge
-Otalgia: Pain in the ear
(refer to slide 12 for more details)
What is Otitis Externa and its properties?
-Inflammation of the skin of the external ear
-The tissue responds to the inflammation by edema or swelling, redness & otalgia
-The swelling increases the tension on the epithelium making it quiet painful
What is ear wax and its properties?
-wax is the most common cause of conductive hearing loss in adults
-some people have extremely active wax glands
-improper use of ear cotton swaps or buds, pushing the wax to the bony portion (contraindicated)
-some times water pressure during diving may push the wax further into the canal
-symptoms may include itching, otalgia, and sensation of fullness in the ears
-amount of hearing loss depends on the amount of ear canal occlusion and impaction to TM
What is the tympanic membrane (TM)?
-it marks the boundary between the outer and middle ear
-concave, and slightly oval structure
-approximately 55 mm^2 in area
-semi-transparent
What are the 3 composed layers of tissue in the tympanic membrane?
-Outer (Cuticular) layer —> epithelium
-Intermediate (Fibrous) layer —> fibrous connective tissue
-Inner (mucous) layer
Point out the landmarks of the tympanic membrane:
refer to slide 23
What are the landmarks of the tympanic membrane?
-Umbo is the most depressed portion
-The light reflex is cone shaped
-Pars falccida on the upper portion of the TM lacks the fibrous layer
-Pars Tensa is the greatest surface on the TM
-Tympanic annulus is a ring of tissues that hold the TM in position at the end of EAC
-The direct of the cone of light and the handle of malleus give an indication of which ear is being tested
-The handle of malleus runs at 11 o’clock in the left ear
Function of the TM:
-The vibration of acoustic energy in air in EAC is transmitted into mechanical energy by TM and ossicles of middle ear to footplate of the stapes
-Amplification of sound by:
1- aerial (space) factor between TM & footplate of stapes
2- lever function of ossicles, the overall will be around 20-23 dBS
-Protection of INNER ear by acoustic stapedius muscle reflec (ASMR)
Function of Inner ear & 8th Nerve:
-The footplate of the stapes will convert the sound into hydrolic energy in peri & endo lymph moving the basilar membrane & organ of Corti. The sound energy will be in form of chemico-electrical in Hair Cells and these will be transduced into electrical form in the dendrites of the cochlear nerve. This process is called transduction of the inner ear (transducer)
Concha is divided into two parts:
1) Lower cavum concha
2) Upper cymba concha
