Anatomy And Physiology Flashcards
What is anatomy?
What it is add what it does (function)
What is physiology?
How it does it
Superior?
Upper
Inferior?
Lower
Anterior?
Front
Posterior?
Back
Medial?
Middle
Lateral?
Towards the side
Inter?
In between
Anti?
Opposite
What is the pinna made up of?
Cartilage, epithelium & lobule
Which 3 nerves are located within the ear?
Cranial v, facial vii & vagus x
13 parts of the outer ear?
Helix, anti helix, crus of helix, superior crus of helix, inferior cross of helix (5)
Tragus and antitragus (2)
Scapphoid fossa and triangular fossa (2)
Lobule, inter tragic notch, Darwin’s tubicle and concha (4)
Characteristics of the EAM
2.5 cm long
7/8mm in diameter
4cc in volume
First third is cartilage 1.5mm thick
2nd 2/3’s is bone 0.5mm thick
Contains sebaceous and ceruminous glands
Has 2 distinct bends - isthmus narrowest point
Main function of the whole ear?
Transform acoustical energy into neural codes that are interpreted by the brain as sound
8 parts of the EAM?
Hairs
Sebaceous and ceruminous glands
Cartilage
Bone
Epithelium 1.5mm thick - start
Epithelium 0.5mm thick - finish
1st bend
2nd bend
What is cerumen?
Secretive sebaceous (oil), ceruminous (sweat) mix with dirt and debris to create Wax
Properties of Cerumen (7)
Colour variable
Water resistant
Hygro scopic
Acidic
Bacteriostatic
Lubricant
Migration - self cleaning
Parts of the TM (10)
Pars tensa pars flacidda
Annulus
Light reflex
Umbo
handle of Malleus
Short process of malleus
Long process of incus
Anterior malleal fold
Posterior malleal fold
TM made up of which 3 layers?
Squamous epithelium
Fibrous layer
Mucous membrane
Properties of the TM (8)
10mm high x 8mm wide 0.1 thick
Approx 55 degree angle
Concave - umbo max point of concavity
Translucent pearly grey
Handle of Malleus attached
Light reflex
Annulus
3 layers
What is the function of the outer ear?
CLAP
Collection
Localisation
Amplification
Protection
What is the resonance of the concha and EAM? What is their maximum amplification?
Concha resonates at 5500Hz
EAM at 2500Hz
Max amplification when combined is 3000Hz
(Increases signal by 15-20dB)
How does the pinna protect the middle ear?
Tragus - obstructs canal opening (objects/trauma)
Meatus: wax (protection against infection)
Hairs (filter/barrier)
2 bends (objects/trauma)
Sensitive bony section (cough reflex)
What is the function of the TM?
VATS
vibrates exactly in tune with incoming sound
Acoustic to mechanical energy
Transmits further into auditory system
Shield between outer and inner ear
Describe the Middle ear.
ME is an air filled chamber with a mucous membrane lining (lining continues in from 3rd layer of TM). It is surrounded by the Mastoid bone.
What makes up the ossicle chain?
Malleus, incus and stapes bones
Characteristics of the Eustachian tube
Approx 36mm long
Mucous membrane continuous with lining from tympanic cavity
1st 1/3 is cartilage
2nd 2/3 is bone
Tensor palatini muscle contracts to open and close the ET to allow EQUALISATION OF PRESSURE
links with NASOPHARYNX to drain mucous out of ME
Wheat does the stapes bone tap on?
The oval window - then comes the cochlea promontory and then the round window which leads into the inner ear.
What are the 3 muscles in the middle ear and their function?
Tensor tympani attached to MALLEUS and is next to TM. Also contracts to reduce head trauma (non acoustic reflex)
Stapedius muscle attached to stapes and also contracts to very loud sounds to protect inner ear.
Tensor palatini attaches to Eustachian tube and acts like a valve for drainage
Each muscle helps keep parts in place
Function of the middle ear?
TCAP
Transducer- converts acoustic to mechanical energy
Conduction - sounds from outer to inner ear
Amplifier - transformer, action, impedance mismatch mechanism
Why do we need equal pressure between outer and middle ear?
To allow effective conduction of sound to travel through. Otherwise sound will be compromised ie TM doesn’t vibrate as well
What is the function of the Eustachian tube?
Equalise pressure - either side of TM necessary for optimal hearing
Ventilation - tensor palatini muscle operates like a valve
Drainage - ET connects ME to nasopharynx for drainage of mucus
What is impedance?
A mediums resistance to movement
Low impedance - moves easily
High impedance - requires more force to move through medium ie water more difficult than air
What are the 3 mechanisms of the ME to mitigate impedance mismatch?
Aeral ratio
Leverage action
TM characteristics
Explain the areal ratio in relation to the impedance mismatch
TM is 14 x larger than oval window condensing sound pressure into smaller area - SPL is then increased although sound is not louder.
Explain leverage action in relation to impedance mismatch
Malleus is 1.15 x longer than incus which is equal to a 1:1.3 pressure increase
Explain TM characteristics in relation to impedance mismatch
Conical shape of TM helps condense increasing SPL towards stapes and oval window
How much do the 3 impedance mismatch mechanisms increase SPL by?
22 times greater - the combined nature increases the SPL sufficiently to move the sound from the air of the ME through the fluids of the inner ear.
Explain the acoustic reflex
This is the stapedius muscle contracting in response to loud sounds (70-80dB above their hearing threshold) which reduces movement to the ossicles which become tense. This is attempting to protect the inner ear from the excessive, potentially damaging, sound.
This is always bilateral but not instantaneous hence sounds can damage ie explosions
Explain the non acoustic reflex
Occurs when the tensor tympani muscle (located next to TM and supports malleus) contracts in response to a puff of air on the cornea likely in response to head trauma.