Ear Flashcards
What are the 3 sections of the ear?
- External
- Middle
- Inner
What structure separates the external and middle ear?
Tympanic membrane
What are the parts of the external ear?
- Helix
- Triangular area
- Tragus
- Meatus
- Concha
- Antitragus
- Antihelix
- Lobule
What type of cells form the skin of the pinna?
Stratified keratinized epithelium
What is present that gives the pinna its structure?
Elastic cartilage
How long is the external ear in adults?
4cm
What is the lateral 1/3 of the external ear made from?
Skin and cartilage
What does the skin of the lateral 1/3 of the external ear contain?
Ceruminous and sebaceous glands
What does the lateral 1/3 of the external ear act as?
Protective barrier and disinfectant
How do the hairs in the ear differ throughout?
Thick hairs on the outside becoming finer inside
What is the medial 1/3 of the external ear made from?
skin and bone
What is not present in the medial 1/3 of the external ear but is in the lateral?
- Hairs
- Cilia
What does the medial 1/3 of the external ear not produce?
Wax
What constantly happens to the skin of the external ear?
Constantly being shed and renewed
Where does the skin of the external ear canal grow from?
Umbo of the tympanic membrane outwards
Where is skin of the external ear canal shed from?
Lateral 1/3rd of canal and trapped in wax as part of cleaning mechanism
What part of the ear is not very good at sound localisation in humans?
Pinna
What causes minimal hearing loss when compared with problems in other parts if the ear?
Wax or mechanical obstructions
Name the parts of the tympanic membrane?
- Posterior fold
- Incus
- Umbo
- Annulus
- Pars tensa
- Cone of light
- Manubrium of malleus
- Short process of malleus
- Anterior fold
- Pars flaccida
What are the 3 layers of the tympanic membrane?
- Outer layer that is continuous with kin of EAC
- Middle fibrous layer
- Inner layer of respiratory epithelium (ciliated columnar epithelium with goblet cells)
How thick is the tympanic membrane?
1/10th of a millimeter
What diameter is the tympanic membrane?
1cm
What are the 3 bones found in the inner ear?
- Head of malleus
- Incus
- Stapes
What do the ossicles do?
- Conduct sound waves from tympanic membrane to inner ear
- Play a very important role in sound conduction
What can disruption of the ossicles be from?
Trauma or bony sclerosis (otosclerosis)
What is the middle ear lined with?
Same continuous respiratory epithelium that forms inner layer of tympanic membrane
What is the middle ear capable of producing?
Mucous
What can the production of excess mucous in the middle ear lead to?
Glue ear
What does the middle ear connect to the mastoid system via?
Aditus
What does the middle ear connect to the nasopharynx via?
Eustachian tube
What nerve foes the middle ear contain?
Chorda tympani branch of the 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 segment of the facial nerve?
- Intracranial
- Meatal segment (internal auditory meatus)
- Labyrinthine segment
- Tympanic segment (Fallopian tube. 10% which are dehiscent)
- Mastoid segment
- Extratemporal segment
What does the facial nerve supply motor function to?
Muscles of facial expression
- Stapedius
- Posterior belly of digastric
- Stylohyoid
Where does the anterior 2/3rds of the tongue receive taste from?
Chorda tympani
What structures can be affected by complications of otitis media and cholesteatoma?
- Meninges
- Middle cranial fossa
- Facial nerve
- Mastoid cavity
- Inner ear
- Sigmoid sinus/internal jugular vein
Cholesteatoma
Keratinised squamous epithelium (skin) in the wrong place
How does cholesteatoma cause problems?
They grow and are destructive
What are the 2 types of cholesteatoma?
- Congenital
- Acquired
What nerve is associated with the inner ear?
Vestibulocochlear nerve (CN VIII)
What are the components of the inner ear?
- Bony and membranous labyrinth
- Cochlear
- Peripheral vestibular apparatus
Cochlear
Organ of corti- hearing organ
What are the 3 components of the peripheral vestibular apparatus?
- Utricle
- Saccule
- Semi-circular canals
What does the membranous labyrinth of the inner ear contain?
Fluid
- Perilymph
- Endolymph
What is the function of the middle ear?
Transduce vibration into nervous impulses
What is the physiology of hearing following the transduction of vibration into nervous impulses by the middle ear?
- Foot of stapes vibrates in oval window
- Causes pressure wave through fluid in cochlear
- This is detected by hair cells in organ of corti
- Transmitted to brainstem by CN VIII
What is responsible for detecting head rotation?
Semi-circular canals
Vestibulo-occular reflex
What makes you able to fix your vision on an object even when your head is moving
What does the saccule detect?
Linear acceleration in vertical plane
What does the utricle detect?
Linear acceleration in horizontal plane
What is another name for the tympanic branch of the glossopharyngeal nerves CN IX?
Jacobson’s nerve
What is Jacobson’s nerve responsible for?
Sensation to middle ear
What is another name for the auricular branch of the vagus nerve CN X?
Arnold’s nerve
What is Arnold’s nerve responsible for?
Sensation to posterior half of EAC
What is the facial nerve responsible for?
Anterior half of EAC
What is the mandibular branch of the trigeminal nerve responebile for CN V3?
Pinna
When can otalgia be a worrying sign?
In the absence of an obvious ear cause as it could be due to head and neck cancer
