anatomy of ear Flashcards
functions of external ear?
receives sound waves
functions of middle ear?
Transmits sound waves from air to bone
Amplifies by bone to bone
Transmits sound to inner ear
functions of inner ear?
Sound waves converted to nerve impulses
Transmitted to CNS via acoustic nerve (CNVIII)
Vestibular organs
what type of epithelium is the pinna
Stratified keratinized epithelium – skin.
what type of cartilage is the pinna?
elastic cartilage
where does the pinna get its blood supply from?
overlying Dense connective tissue/perichondrium
what does the skin contain of th lateral 1/3 of external ear canal
containing ceruminous and sebaceous glands.
true or false:
the ear has modified sweat gland producing wax
true
does the medial 2/3 of external ear canal have hairs or produce wax?
no
where does the skin grow from- external ear canal
umbo of the tympanic membrane outwards
what are the three layers of the tympanic membrane?
Outer layer is continuous with skin of EAC.
Middle fibrous layer
Cuboidal epithelium
what are the contents of the middle ear?
Ossicular chain Oval window Round window Facial nerve (usually covered in bone) Chorda tympani Eustacian tube opening Includes mastoid air cells
what are the three ossicles of the year?
malleus
incus
stapes
function of the ossicles
Conduct sound waves from tympanic membrane to inner ear via oval window
function of middle ear
transduce vibration into nervous impulses
function of the eustacian tube
- Pressure equalisation
Middle ear lined with respiratory epithelium
Gas exchange happens
Vacuum formed in middle ear
Vacuum released on opening of eustacian tube - Mucus drainage
otitis media with effusion
Eustacian tube not opening
negative pressure
Fluid drawn into middle ear
Fluid filled ear limits mobility of ossicular chain
what is cholesteatoma?
Negative pressure Sucks in Tympanic membrane Retraction pocket Normal skin growth - umbo out Over time Enlarges retraction pocket Skin no longer comes out of pocket Enlarging ball of keratin into middle ear Slowly destroys and invades structures
complications of otitis media and cholesteatoma
Remember anatomical relations Meninges Middle cranial fossa Facial nerve Mastoid cavity Inner ear Sigmoid sinus/internal jugular vein
6 segments of the facial nerve
Intracranial
Meatal segment (internal auditory meatus)
Labyrinthine segment
Tympanic segment (Fallopian tube. 10% of which are dehiscent. i.e within mucosa)
Mastoid segment
Extratemporal segment
motor supply to the muscles of facial expression
Stapedius
Posterior belly of digastric
Stylohyoid
5 branches of the facial nerve
Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical
what are the peripheral vestibular apparatus?
urticle
saccule
semicircular canals
what are Semicircular canals responsible for?
detecting head rotation
function of the saccule
detects linear acceleration in vertical plane
functions of the urticle
detects linear acceleration in horizontal plane
contents of external ear
Pinna and EAC
contents of the middle ear
Tympanic membrane, ossicles
Lots of important things in and around
contents of inner ear
Organ of corti – hearing
Semicircular canals/utricle/saccule – one part of balance
