Lec 1 Flashcards
Parts of the ear ?
1- inner ear
2- middle ear
3- external ear
Parts of external ear ?
1- auricle
2- EAC
3- tympanic memebrane ( drum)
Talk about the auricle ?
1- helix : outer rolled edge
2- antihelix : y shaped anterior to helix
3-triangler fossa : y limbs
4- concha : depression anterior , below antihelix
5-cymba concha : ( helix dividing the concha)
If tenderness ~> mastoditis as it the surface anatomy for it
6- tragus : ridge( cover) for the meatus
7- lobule : fat covered with skin
8- incisura terminalis : between root of helix, tragus
Talk about EAC?
(5)
1- 24 mm ( 1 inch )
2- 1/3 cartilgneous , 2/3 bony
3- outer 1/3 :
• thick skin
• hair follicles
• ceruminous glands
• sebeceous glands
• upwards backwards medially
- inner 2/3
• thin skin
• devoid
• downwards forwards medially
4- 2 constrictions
• bony cartilgenous junction
• 5mm before drum ( isthmus)
5- groove called tympanic sulcus which lodge with the tympanic annulus
Talk about tympanic membrane ?
(10)
1- oval
2-oblique ( 55 with the floor)
3- pearly white
4-9*8 mm
5- concave
6-consists of
• handle of mallus
• lateral process
• post malleolar fold
• ant malleolar fold
• cone of light
• umbo : the most depressed part
7-parts
• pars flaccida : upper 1/3 of it , has no fibrous layer
• pars tensa : lower 2/3 of it, has fibrous layer forming annulus around it
8- layers
* outer skin: continuous with EAC
* middle fibrous : thick due embedding of handle of mallus regarding being fibre
* inner mucosal : continuous with that of ME
9- 0,1 mm in thickness
10- more thick in children ~> more complications
When exposure to high pressure which part of TM will explode first ?
Pars tensa 😁
Parts of middle ear ( middle ear cleft) ?
1- ME cavity
2- eustachian tube
3- mastoid air cells
Talk about ME CAVITY ?
(3)
1- divided to
• attic ( epitympanum )
Continous with antrum through aditis ad antrum
• mesotympanum
Level of TM
• hypotympanum
Below the level of TM
2- walls 🤍
• roof : thin bony plate called tegman tympani separates it from temporal lobe
• floor : very thin bony plate separates it from jugular bulb (can be dehiscent sometimes ~> pulsatile tinnitus)
• anterior :
3 canals
* tensor tympani canal
* eustachian tube
* ICA canal ( if aneurysm ~> pulsatile tinnitus)
• posterior :
3 structures
* pyramid : contains stapedius
* aditis
* vertical part of facial n canal
• medial :
6 structures
* promontry : by first turn of cochlea
* oval window : closed by footplate of stapes
* round window : covered by secondary tympanic membrane
* sinus tympani : depression in between
* processes cochlearformis : pulley like projection above promontry in which tendon of tensor tympani lodge forming 90
*transvers part of facial n canal
• lareral : TM
3- contents
• 3 bones : malleus incus stapes
• 2 muscles : stapedius ( facial )
Tensor tympani (trigeminal)
• 2 nerves: tympanic plexus ( 9)
Chorda tympani (7)
• air by eustachian tube
Talk about eustachian tube ?
(8)
1- 36 mm
2- 1/3 bony ,2/3 cartilgenous
3- c shaped cartilage
4- opens while swallowing, yawning by levater, tensor palati
5- lower opening is 1 cm from the posterior part of inferior turbinate of nose
6- forward , downward medially to nasopharynx
7- more shorter wider horizantal in children thus otits media is more common in children
8- children with cleft palate usually have secretory otits media
Talk about mastoid air cells
(3)
1- cavities lined by mucous membrane conitinous with eachother
2- parts
- antrum :
•the largest air cell
• in its medial wall, there is 2 features lateral scc , 2nd genu of facial n
- peri antral cells
- sigmoid sinus
- peri sinus cell
- sinu dural cells
- tip cells
- zygomatic cells: in zygomatic bone
- retro facial cells
- type
• diploic ( bone marrow ) in children
• cellular ( pneumatic) in 85%
• acellular ( sclerotic) in 15%
Parts of inner ear ?
1- bony labyrinth
2- membranous labyrinth
Talk about bony labyrinth
1- vestibule :
• the central part
• oval and round window appear in its lateral wall
2- scc
• lateral , post and sup
• 5 openings
• has a swelling in each end called ampulla
• contains sc ducts
3- cochlea
• 2/5 turns
• around modiulus that contains spiral ganglia connected to cochlear n
• its apex is anterolateral while the base is posteromedial
• 3 compartments
- scala vestibuli
* lined by reissner membrane
* contains perilymph
* it ends at the oval window closed by footplate of stapes
- scala tympani
* lined by basilar membrane
* contains perilymph
* ends at the round window closed by secondary tympanic membrane
- scala media ( cochlear duct)
* contains endolymph
* contains organ of corti
• scala vestibuli , tympani connected together at apex of cochlea helicotrema ( cochleotrema)
Talk about membranous labyrinth
•cochlear duct ( scala media ) containg the sensory organ ,organ of corti
- triangler in shape
- reissner membrane above , spiral gaglia medial
Basilar membrane below , stria vascularis lateral
• utricle and saccule ( sensory organ is macula containing otolithic membrane)
• sc ducts ( crista ampullaris)
• endolymphatic duct in vestibular aqueduct and sac beneath the dura
Cycle of endolymph
stria vascularis ~> membranous labyrinth ~> endolymphatic duct , sac ~> CSF
Function of middle ear ?
1- conduction : through ossiclar chain
2- amplification : 20 times by
• areal ratio : ratio between surface area of TM and oval window is 17:1
• lever action : ratio between malleus , incus 3:1
And this amplification compensates the decrease in sound when transmitted through fluids of inner ear ( impedence matching mechanism )
