Clinical Anatomy of the Ear Flashcards
What are the 3 anatomical divisions of the ear?
External
Middle
Inner
What are the 2 functional divisions of the ear?
Hearing (auditory)
Balance (Vestibular)
Where are all divisions of the ear found?
In the temporal bone
What nerves are found in the temporal bone?
Facial (CNVII)
Vestibulocochlear (CN VIII)
What are 6 features of the temporal bone?
Squamous part Petrous part Zygomatic process External acoustic meatus Mastoid process Styloid process
What is the thinnest part of the skull?
Pterion
What makes up the pterion?
Frontal bone
Parietal bone
Temporal bone
Sphenoid bone
What cranial nerve enter/exit the the skull in the frontal bone?
CN 1
What cranial nerve enter/exit the the skull in the middle region of the base of the skull/
CN 2,3,4,5,6
What cranial nerve enter/exit the the skull in the occipital region of the skull?
CN 7,8,9,10,11,12
What 3 things pass through the internal acoustic meatus?
CN VII
CN VII
Labyrinthe artery and vein
What does the facial nerve supply?
Motor to face Motor to stapedius Taste to anterior 2/3rds of tongue Secretomotor to salivary and lacrimal glands General sensation to external ear
What does the vestibulocochlear nerve supply?
Balance
Hearing
Where does the labyrinthine artery come from?
Circle of willis
Branch of anterior inferior cerebellar artery
Where is the external ear?
Auricle to tympanic membrane
What is the function of the external ear?
Collects and conveys sound waves to tympanic membrane
Where is the middle ear?
Tympanic membrane to oval window + eustachian tube
What is the function of the middle ear?
Amplifies and conducts sound waves to the internal ear
Where is the internal ear?
Oval window to internal acoustic meatus
What is the function of the internal ear?
Converts special sensory information
What does the internal ear convert special sensory information into?
Fluid waves
The Action Potentions
Conducts AP to brain
What is the skeletal part of the external ear?
Temporal bone
Elastic cartilage
Avascular
Nutrients from skin
Where does the ear canal begin?
At the external acoustic meatus
What is the ear canal composed of?
1/3rd cartilage
2/3rds bone
What is the ear canal lined with?
Skin
What does the ear canal produce and how?
Earwax via ceruminous glands
What nerves are involved in supplying the auricle?
C2,3 spinal nerves (Helix, Antihelix)
CNV3 - superior parts of EAM and most of tympanic membrane
CNX (Inferior parts of EAM and tympanic membrane0
Where does the lateral surface of the superior auricle drain to?
Parotid Lymph nodes
Where does the cranial surface of the superior half of the auricle drain to?
Mastoid and deep cervical lymph nodes
Where does the rest of the auricle including the lobe drain to?
Superficial cervical lymph nodes
Where does all lymph from the auricle eventually drain to?
Deep cervical
Thoracic or right lymphatic duct
What is involved in otoscopic examination?
Examination of the EAM and tympanic membrane
What shape in the EAM in a child?
Short and staight
What shape is the EAM in children?
Curved
What is the thin part of the tympanic membrane called and where is it found?
Pars flaccida
Superiorly
What is the most inwardly depressed part of the tympanic membrane?
Umbo
What is the thick part of the tympanic membrane and where is it found?
Pars tensa
Posteroinferiorly
What supplies the external surface of the tympanic membrane?
CN V3
What supplies the internal surface of the tympanic membrane?
CN IX
What does the glossopharyngeal nerve provide sensory innervation to?
Middle ear cavity Eustachian tube Nasopharynx Oropharynx Tonsils
What does the eustachian tube connect?
The tympanic cavity to the wall of the nasopharynx
What 3 bones does the middle ear contain?
Malleus
Incus
Stapes
What 2 muscles are found in the middle ear?
Stapedius
Tensor tympani
What nerves have branches in the middle ear?
Facial nerve
Glossopharyngeal nerve
How do auditory ossicles articulate?
Via synovial joints
Where is the epitympanic membrane found?
Superior to tympanic membrane
Which bone in the middle ear does not have a muscle attachment?
Incus
What is the roof of the tympanic cavity?
Tegmental wall
What is the floor of the tympanic cavity?
Jugular wall
WHat is the lateral wall of the tympanic cavity?
Membranous wall
What is the medial wall of the tympanic cavity?
Labyrinthine wall
WHat is the posterior wall of the tympanic cavity?
Mastoid wall
What nerve supplies the stapedius muscle?
CN VII
What nerve supplies to tensor tympani muscle?
CN V3
What is the eustachian tube?
Auditory pharyngotympanic tube
Why can tonsilitis mimic ear ache?
Common sensory nerve supply
What is the sensory supply to the nasopharynx/Oropharynx?
CN IX
What is the sensory supply to the laryngopharynx?
CN X
What is the chorda tympani?
A branch of the CN VII
What does the chorda tympani supply?
Taste buds to anterior 2/3rds of the tongue
Parasympathetic to submandibular and sublingual salivary glands
What does the stapedius do?
Reduced stapes movement to protect the internal ear from excessive noide
What does the chorda tympani connect to?
Lingual nerve branch of CN V3
What are the 4 muscles of facial expression?
Frontalis
Orbicularis oculi
Elevator of lips
Orbicularis oris
Where do muscles of facial expression originate/Insert?
Originate on bone
Insert into superficial fascia
What are the 2 parts of CN VIII in the inner ear?
Cochlear nerve (hearing) Vestibular nerve (balance)
Where is the otic capsule found?
Temporal bone
What does the otic capsule contain?
Bony labyrinth
Fluid (perilymph) filled spaces inside
What is suspended within perilymph of the bony labyrinth?
Membranous labyrinth
Communicating sacs and ducts
Contains enolymph fluid
What are 6 features of the inner ear labyrinths?
Superior semicicular canal Lateral semicircular canal Posterior semicircular canal Cupula (apex of spiral) Oval window Round window
What is the cochlear duct?
A long balloon like structure within the cochlea filled with endolymph
How are action potentials from the cochlear duct conducted to the brainstem?
In the cochlear nerve
What are the semicircular ducts?
Inter-linked balloon-like structures within the semicircular canals filled with endolymph
How are action potentials from the semicircular canals conducted to the brainstem?
Vestibular nerve
What stimulates hair cells?
Movement of endolymph
What are clusters of hair cells found in?
Regions called maculae
What do semicircular ducts detect?
Angular movement change
What movement does the saccule detect?
Vertical
What movement does the utricle detect?
Horizontal
How is sound transmitted?
Sound waves make the tympanic membrane vibrate
Vibrations are transmitted through ossicles
Base of stapes vibrates in oval window
Vibration of stapes created pressure waves in perilymph
Hair cells in the cochlea are moved, APs are stimulated and conveyed to brain by cochlear nerve
Pressure waves descend and become vibrations again
Pressuve waves are dampened at the round window
What detect auditory stimuli?
Receptor cells in the organ of corti
Where is the organ of corti?
Located on basilar membrane
What are the 2 parts of the cochlear canal?
Scala vestibuli
Scala tympani
What separates the cochlear canal into 2 parts?
Spiral ligament