A28 - Clinical Anatomy of the Ear Flashcards
what is the thinnest part of the skull that is a H-shape and joins the frontal, parietal, temporal and sphenoid bones?
pterion
what 2 parts of bone make up the temporal bones?
squamous and petrous
what nerves are contains in the temporal bone?
facial (CN VII)
vestibulocochlear (CN VIII)
what is the function of the external ear ?
collects and conveys sound waves to tympanic membrane
what are the borders of the external ear ?
auricle to the tympanic membrane via the external acoustic meatus
what is the function of the middle ear ?
amplifies and conducts sound waves to the internal ear
what are the boundaries of the middle ear ?
tympanic membrane to the oval window
what important structure which connects the ear to the nasopharynx does the middle ear contain?
eustachian tube
what is the function of the internal ear ?
converts special sensory information
- into fluid waves
- then APs
- conducts APs to the brain
what are the boundries of the internal ear ?
oral window to the internal acoustic meatus
what parts of the skeleton make up the external ear?
temporal bone
what type of cartilage is the external ear made of?
elastic cartilage
how does elastic cartilage gain the nutrients it requires?
avascular so gets nutrients from the skin and mucosa surrounding it
when injecting anaesthetic near the ear what should this not contain?
adrenaline
how does the ear canal produce earwax?
via ceruminous glands
what is the sensory supply of back of the ear, the helix and the ear lobe?
C2,3 - great auricular
what area of the ear does the CN Va (mandibular nerve)?
superior parts of the external acoustic meatus and most of the tympanic membrane
what is the sensory supply to the inferior part of the EAM and tympanic membrane?
CN X - branch of the vagus nerve called alderman nerve
what is the lymphatic drainage of the lateral surface of the superior half of the ear ?
parotid lymph nodes
what is the lymphatic drainage of the cranial surface of the superior half of the ear ?
mastoid lymph nodes (deep cervical lymph nodes?
what is the lymphatic drainage of the rest of auricle including the lobe?
superficial cervical lymph nodes
what is the overall drainage of the lymph of the overall ear?
deep cervical lymph nodes > thoracic duct or right lymphatic duct > venous angle
what is a otoscopic examination?
examination of the EAM and tympanic membrane
Which direction would you pull a child’s ear during an otoscopic examination
Posteroinferiorly
Which direction would you pull a adult’s ear during an otoscopic examination?
Posterosuperiorly
what are the characteristics of a child’s EAM?
short and straight
what are the characteristics of an adults EAM?
curved
what is the most inwardly depressed part of the tympanic membrane?
umbo
what is the thin part of the tympanic membrane that sits superiorly?
pars flaccida
what is the thick part of the tympanic membrane which sits posteroinferiorly?
pars tensa
What innervates the external surface of the tympanic membrane?
CN V3 (auriculotemporal nerve)
What innervates the internal surface of the tympanic membrane?
CN IX - glossopharyngeal
What does the glossopharyngeal nerve supply sensory innervation to?
- middle ear cavity
- eustachian tube
- nasopharynx
- oropharynx
- tonsils
what connects the tympanic cavity to the lateral wall of the nasopharynx>
eustachian tube
what causes referred pain of tonsilitis or pharyngisits ?
eustachian tube
In what part of the ear are the malleus, incus and stapes bones?
Middle ear
what are the 3 auditory ossicles?
malleus
icnus
stapes
What two muscles are in the middle ear?
Stapedius and tensor tympani
What connects the middle ear cavity to the nasopharynx?
Pharyngotympanic Tube
What type of joints do the auditory ossicles articulate by?
Synovial
What creates the umbo of the tympanic membrane?
Handle of Malleus
What branch of the facial nerve passes through the tympanic cavity?
Chorda Tympani
What muscle reduces the stapes movement? It is the tinniest skeletal muscle in the body and is supplied by CN VII)
Stapedius
what is the right promontory?
bony swelling on the medial wall formed hy the cochlea of the internal ear
what is the aditus?
doorway into the mastoid antrum form he epitympanic recess
what causes mastoditis?
spread of infection to the mastoid air cells from the middle ear cavity
what is the pathway of the facial nerve through the middle ear cavity?
- comes from the pons-medullary junction and exits via the internal acoustic meatus
- travels in the facial canal of teh petrous temporal bone
- then exits via the stylomastoid foramen
what is the thinnest skeletal muscle in the body which is supplies by CN VII that reduces stapes movement to protect the internal ear from excessive noise?
the right stapedius muscle
what is the extracranial course of the facial nerve?
- exits via the stylomastoid foramen
2. branches off to supple muscles of facial expression
what is the pathway of the chorda tympani?
- branches from the facial nerve and exits the skull via stylomastoid foramen
- follows the lingual branch of CN V3 to synapse at the submandibular ganglion
- post-ganglionic fibres then supple the submandibular and sublingual glands
where is the internal ear located?
petrous part of the temporal bone
what nerve supplies the internal ear?
CN VIII - vestibulocochlear
what are the two parts of CN VIII?
- cochlear nerve for hearing
- vestibular nerve for balance
what is contained in the otic capsule?
bony labyrinth
what fills the bony labyrinth?
perilymph (similar to extracellular fluid?
what is suspended within the perilymph of the bony labyrinth?
- membranous labyrinth
- communicating sacs
- endolymph fluid
what part of the otic capsule is resposnsibel for hearing?
cochlea - sprial which has 2 turns ending in an apex
what part of the otic capsule is responsible for balance?
the three semi-circular canals
what is teh long balloon like structure within the cochlea filled with endolymph?
cochlear duct
what are the inter-linked balloon like structures within the semi-circular canals filled with endolymph?
semi-circular ducts
what are clusters of hair cells in the ear?
maculae
what do semi-circular ducts detect?
angular movement changes
what detects linear movement changes?
utricle and saccule
Descibe the 6 stages of sound transmission?
- Sound waves make the tympanic membrane vibrate
- Vibrations transmitted through ossicles
- Base of stapes vibrates in oval window
- Vibration of stapes creates pressure waves in perilymph
- Hair cells in the cochlea are moved, neurotransmitter is released, Aps stimulated and conveyed to brain by cochlear nerve
- Pressure waves descend and become vibrations again
What are the symptoms of CN VII associated with pathology at the internal acoustic meatus?
- ipsilateral loss of facial expression
- ipsilateral loss of taste
- dry mouth
- reduced general sensation in the auricle
What are the symptoms of CN VIII associated with pathology at the internal acoustic meatus?
- ipsilateral loss of hearing (cochlear nerve)
- ipsilateral loss of balance (vestibular nerve)