Lecture 9 - Anatomy + Ear Conditions Flashcards
What are the 3 parts of the ear?
External ear
Middle ear
Inner ear
What are some signs and symptoms of ear diseases in general?
Hearing loss
Otalgia
Otorrhoea
Tinnitus
Vertigo
Facial nerve lesions/palsy
What is otalgia?
Ear pain
What is otorrhoea?
Ear discharge
What is tinnitus?
When sound is perceived but is not actually coming from an external source
Like ringing, humming and whistling…
What situation does facial nerve lesion/palsy occur as a result of ear disease and why?
Disease of the middle ear
Since the facial nerve (VII) runs through the canal of the Petrous bone
What makes up the external ear?
Pinna
External auditory meatus
External auditory canal
Lateral surface of tympanic membrane
What is the pinna/auricle?
The outside cartilaginous bit of the ear which most people refer to as the ear
What type of cells line the external auditory canal?
Keratinised squamous epithelium
What is the tympanic membrane?
What everyone refers to as the ear drum
What type of cavity is the middle ear?
Air filled cavity
What is found in the air filled cavity of the middle ear?
Ossicles
What structures does the middle ear connect to?
Nasopharynx via Eustachian tube/pharyngotympanic tube (PT)
Mastoid process
Sigmoid dural venous sinus
What fills the ducts/tubes of the inner ear?
Fluid
What are the structures of the inner ear?
Vestibulocochlear nerve (VIII)
Semicircular canals
Vestibule = utricle + saccule
Cochlea
What are the ossicles in the ear from attached to the tympanic membrane to deep?
Malleus
Incus
Stapes
Go to the last slide and label the ear:
1 = Pinna
2 = External auditory canal/meatus
3 = Tympanic membrane
4 = Malleus
5 = incus
6 = stapes
7 = Eustachian tube/pharyngotympanic tube
8 = cochlea
9 = semicircular Canals
10 = cochlear nerve
11 = vestibular nerve
12 = external ear
13 = middle ear
14 = internal ear
What cells line the inner ear?
Sterocilia
What is the important bone relevant to the ear?
Temporal bone (Petrous part in particular)
What are the 2 membranous sacs making up the vestibule portion of the inner ear?
Utricle
Saccule
Which of the 2 membranous sacs of the inner ear (vestibule) receive the 3 semicircular canals?
Utricle
What does the saccule connect to?
Cochlea
What are the nerves supplying the external ear with general sensation?
Cervical nerves C2 and C3
Trigeminal nerve
Vagus
CN VII
What nerve supplies the middle ear cavity and medial surface of tympanic membrane with sensation?
Glossopharyngeal (IX)
What are some causes of refered pain to the ear (non ontological causes of otalgia)?
TMJ dysfunction
Oropharyngeal disease like pharyngitis
Laryngeal and pharyngeal cancers
Why can TMJ dysfunction lead to otalgia?
TMJ supplied by the Mandibular division of the Trigeminal nerve (Vc)
The auriculotemporal nerve supplying the ear is a branch of the mandibular division of the Trigeminal nerve (Vc)
Why can pharyngitis lead to referred ear pain?
Pharynx supplied by the Glossopharyngeal nerve (IX)
Glossopharyngeal nerve supplies middle ear
Why can laryngeal and pharyngeal cancers cause referred pain?
Pharynx and larynx supplied by CN IX and X
Middle ear = IX
External ear = X
What is the function of the external ear?
Focuses and transmits sound waves to the tympanic membrane
What is the pinna made of?
Cartilage
Perichondrium
Skin and fatty tissue (lobule)
What is the shape of the external accoustic meatus in adults?
Sigmoid shape
How does the structure of the outer 1/3 and inner 2/3 of the external acoustic meatus differ?
Outer 1/3 = cartilage
Inner 2/3 = bone
Both lined with skin
Which part of the external acoustic meatus is the hair, sebaceous and ceruminuos glands (wax producing) located?
Cartilage part
What happens to the dead desquamed keratinised squamous cells in the external acoustic meatus?
They migrate laterally away from the tympanic membrane where they mix with the wax
What can be seen with an otoscope?
External acoustic meatus
External surface of tympanic membrane
How should the ear be manipulated to view the ear using an otoscope in an adult and why?
Pull up and back
Since sigmoid shape
What bone is usually visible using an otoscope when looking at the tympanic membrane?
Malleus
What is the top of the tympanic membrane called?
Pars flaccida/attic
What is the bottom part of the tympanic membrane called?
Pars tensa
What is visible as a result of the otoscope examination process on the tympanic membrane?
Cone of light
Look at the last slide, label the tympanic membrane structures:
1 = manibrium of malleus
2 = pars flaccida
3 = pars tensa
4 = incus
What nerve can sometimes be visible on otoscopy?
If damaged what symptoms can someone get?
Chords tympani
Lose taste or dry mouth (parasympathetic lost)
What nerve can sometimes be visible on otoscopy?
If damaged what symptoms can someone get?
Chords tympani
Lose taste or dry mouth (parasympathetic lost)
What are white plaques on the tympanic membrane called?
Tympanic sclerosis
What causes tympanic sclerosis?
Previous trauma or irritation leading to healing being needed
What changes can occur to the tympanic membrane with middle ear pathology?
Bulging and erythematous
Or
Over retracted (normally retracted)
Can indicate fluid in middle ear when it should be air
What is the function of the ossicles?
Relay and amplify vibrations from the Tympanic membrane to the oval window which then transmit these vibrations into waves in the fluid of the cochlea
What muscles dampen the vibrations of the ossicles if the nosies are very loud?
Tensor tympani
Stapedius
What is the reflex called when the tensor tympani and stapedius muscles contract when the noise is too loud to dampen the noise?
Acoustic reflex
What is the condition called when the acoustic reflex is ineffective??
Hyperacusis
What can cause hyperacusis and why?
Facial nerve lesion
Since a branch of the facial nerve is the nerve to stapedius , if this is damaged the stapedius muscle wont move the stapes bone
What lines the middle er?
Mucus membrane
What is special about the middle ear in terms of air flow?
Constantly drawing air into it so pressure in there is negative
What structure is important in equalising the negative pressure in the middle ear so it matches the pressure on the external ear side of the tympanic membrane?
Pharyngotympanic tube (Eustachian tube)
What happens to the tympanic membrane if there’s dysfunction in the pharyngotympanic tube?
Negative pressure builds up in middle ear retracting and pulling TM inwards
What diseases are caused by dysfunction of the pharyngotympanic tube?
Otitis media with effusion (glue ear)
Cholesteatoma
Why are problems/complications with the pharyngotympanic tube more common in children/infants?
Its shorter nd more horizontal
More easily blocked
Opens to andenoid tonsils which are larger in kids
Shorter pathway for infections to spread to middle ear
What are some important anatomical features related to the middle ear?
Eustachian tube
Facial nerve
Mastoid cells
Sigmoid dural venous sinus
Brain and cerbellum near (surrounded by meninges)
Why is a middle ear infection potentially dangerous?
Connects to many things
Septic thrombi could form in sigmoid dural venous sinus
Infection could spread to infect the meninges
Abscess could compress brain
Mastoid could get infected
What part of the inner nears is essential for sound?
Cochlea
What part of the inner ear is needed for balance?
Semicircular canals, utricle and saccule
What can disease of the inner ear cause?
Hearing loss
Tinnitus
Balance disturbance and vertigo (vestibular apparatus)
How does the vestibular system detect movement/balance?
Head movements move fluid in the semicircular canals
Movement of this fluid moves the gelatinous matrix which the Sterocilia are embedded
The movement of the Sterocilia generates action potentials to be sent along the vestibular portion of the vestibulocochlear nerve (VIII)
What are the calcium carbonate crystals Called found in the utricle and saccule?
Otoliths
How does the cochlea lead to hearing?
Vibrations of stapes at teh oval window makes waves in the fluid in the cochlea
This moves the Sterocilia in the spiral organ of corti in the cochlea
This generates action potentials to be sent along the vestibularcochlear nerve (VIII)
What is the process of hearing from sound to brain ?
Pinna and external auditory meatus focuses sound onto tympanic membrane
This vibrates which sends vibrations across stapedius, incus to stapes which is at the oval window of the cochlea
Waves generated in cochlear fluid
This is sensed by Sterocilia in spiral organ of corti which generates action potentials in cochlear part of CN VIII
Impulses send to temporal lobe (primary auditory cortex)
Go to the last slide and label the pinna:
1 = helix
2 = superior crus
3 = anti helix
4 = anti Tragus
5 = lobule
6 = tragus
7 = concha
8 = inferior crus
