Anatomy and Physiology of the Ear Flashcards
Parts of the ear
External
Middle
Inner
What makes up the external ear?
Pinna / auricle
External auditory canal
What epithelium is on the pinna?
Stratified keratinised epithelium - skin
What is the pinna made up from?
Elastic cartilage
How long is the external ear canal in adults?
4cm
What is the later 1/3rd of the external ear canal made up from?
Skin and cartilage
What does the skin of the external ear canal contain? What is the function of this?
Cerminous and sebaceous gland. They produce wax
Thick hairs on the outside, becoming thinner on the inside
Function of the external ear canal
Protective barrier
Disinfectant
What is the medial 1/3rd of the ear made up from?
Skin and bone
Does the medial 1/3rd of the ear produce wax?
No
Does the medial 1/3rd of the ear have hairs or cilia?
No
What is a feature of the growth of the skin of the external ear canal?
Constantly being shed and renewed
Grows from the umbo of the tympanic membrane outwards
Shed in the lateral 1/3rd of ear canal and trapped in wax as part of a cleaning mechanism
Is the human pinna good at sound localisation?
No
What are the 3 layers of the tympanic membrane?
Outer layer
- continuous with skin of EAC
Middle fibrous layer
Inner layer of respiratory epithelium
What is the inner layer of respiratory epithelium?
Ciliated columnar epithelium with goblet cells
What is the diameter of the tympanic membrane?
1cm
How thick is the tympanic membrane?
1/10th of a millimetre
Function of the ossicles
Conduct sound waves from the tympanic membrane to the inner ear
What can cause disruption to the sound conduction via the ossicles?
Trauma
Bony sclerosis
What is the middle ear lined with?
Continous respiratory epithelium that forms the inner layer of the tympanic membrane
Can the middle ear produce mucus? What is the clinical relevance of this?
Yes
Glue ear
How does the middle ear connect to the mastoid system?
Aditus
How does the middle ear connect to the nasopharynx?
Eustachian tube
What are the order of the ossicles from tympanic membrane to the oval window, and what is a pneumonic to remember this?
Malleus
Incus
Stapes
MIS
What nerve is found in the middle ear?
Chorda tympani (facial nerve)
What are the most important relations of the middle ear?
Middle cranial fossa
Internal carotid artery
Sigmoid sinus and internal jugular vein
What are the 6 segments of the facial nerve?
Intracranial Meatal (internal auditory meatus) Labyrinthine Tympanic Mastoid Extratemporal
What cranial nerve is the facial nerve?
CN VII
Definition of otitis media
Infection of the middle ear that causes inflammation and a build up of fluid behind the eardrum
Definition of cholesteatoma
An uncommon abnormal condition of keratinised squamous epithelium in the wrong place - can grow and become destructive
What makes up the inner ear?
Bony and membranous labyrinths
Chochlea
Peripheral vestibular apparatus
Vestibulocochlear nerve
What do the membranous labrinths of the inner ear contain?
Fluid
- perilymph
- endolymph
What is the cochlea?
The organ of hearing
What are the peripheral vestibular apparatus?
Utricle
Saccule
Semi-circular canals
What cranial nerve is the vestibulocochlear nerve?
CN VIII
Function of the middle ear
Transduce vibration into nervous impulses
What vibrates into the oval window?
Stapes
What are responsible for detecting head rotation?
Semi circular canals
What is the vestibulo-ocular reflex?
Able to fix your vision on an object even when your head is moving
What does the saccule detect?
Linear acceleration in a vertical plane
What does the utricle detect?
Linear acceleration in a horizontal plane
What provides sensory innervation to the middle ear?
Tympanic branch of glossopharyngeal nerve
What provides sensation to the posterior half of the external ear canal?
Auricular branch of vagus nerve
What provides sensation to the anterior half of external auditory canal?
Facial nerve
What provides sensation to the pinna?
Mandibular branch of trigeminal nerve
What symptom is worrying in the absence of obvious ear cause?
Otalgia
Definition of otalgia
Ear ache
What makes up the external ear?
Pinna
External auditory canal
What makes up the middle ear?
Tympanic membrane
Ossicles
Parts of the tympanic membrane
Crus of the incus
Light cone
Manubrium of the malleolus
Umbo of the malleolus
What drugs taken in high doses can cause tinnitus?
Aspirin
NSAIDs