Clinical Anatomy of Ear Flashcards
The temporal bone can be split into two parts. Name them.
Petrous part
Squamous part
State the name for the thinnest part of the skull
Pterion
List the bones that make up the anterior cranial fossa
Frontal, ethmoid, sphenoid
List the bones that make up the middle cranial fossa
Sphenoid, temporal
List the bones that make up the anterior cranial fossa
Temporal, occipital
Which CN(s) drain into the cribiform plate of the ethmoid bone?
CNI
Which CN(s) drain into the optic canal?
CNII
Which CN(s) drain into the superior orbital fissure?
CNIII, IV, V, VI
Which CN(s) drain into the foramen rotundum?
CNV2
Which CN(s) drain into the foramen ovale?
CNV3
Which CN(s) drain into the internal acoustic meatus?
CNVII, VIII
Which CN(s) drain into the jugular foramen?
CNIX, X, XI
Which CN(s) drain into the hypoglossal canal?
CNXII
List the parts of the external ear
Helix
Ear lobe
Tragus
What connects the auricle to the tympanic membrane?
External auditory meatus
What is the function of the external ear?
Collects and projects sound waves to the tympanic membrane
The middle ear is the ______ to _______
Tympanic membrane
Oval window
What is the function of the middle ear?
Amplifies and projects sound waves to the internal ear
The internal ear is the _____ to ______
Oval window
Internal acoustic meatus
What is the function of the internal ear?
Converts special sensory information into fluid waves, then to action potentials that are sent to the brain
Outline the sensory supply to the skin of the external ear
C2/3 spinal nerve = auricle
CNVII = tragus (small dots)
CNV3 = superior EAM and most of the tympanic membrane
CNX = inferior EAM and tympanic membrane
What is the lymph drainage for the lateral surface of the superior half of the auricle?
Parotid lymph nodes
What is the lymph drainage for the cranial surface of the superior half of the auricle?
Mastoid lymph nodes and deep cervical nodes
What is the lymph drainage for the rest of the auricle including the lobe?
Superficial cervical lymph nodes
The lymph nodes draining the auricle all drain into…
Deep cervical lymph nodes in carotid sheath –> Thoracic venous angle (right lymphatic duct)
What is the skeleton of the external ear composed of?
Temporal bone
Elastic cartilage
What fraction of the EAM is composed of elastic cartilage?
1/3
What fraction of the EAM is composed of petrous temporal bone?
2/3
The ear canal produces _____ which drains into the _________
Ear wax
Ceruminous glands
In what direction would you pull the auricle during ear exam of a child and adult respectively?
Posteroinferiorly
Posterosuperiorly
List the structures making up the tympanic membrane
Pars flaccida (thinnest part of tympanic membrane, superior)
Umbo (inward depressed TM)
Cone of light (anteroinferiorly)
Pars tensa (thickest part of tympanic membrane, posteroinferiorly)
What is the general sensory nerve supply to the external tympanic membrane?
Auriculotemporal branch of CNV3
What is the general sensory nerve supply to the internal tympanic membrane?
Glossopharyngeal nerve
The glossopharyngeal nerve supplies sensory supply to…
Middle ear
Eustachian tube
Naso and oropharynx
Tonsils
List the three auditory ossicles contained within the middle ear
Malleus
Incus
Stapes
The auditory ossicles connect via what type of joint?
Synovial joint
What is the name for the space superior to the tympanic membrane?
Epitympanic recess
What is the name for the space posterior to the tympanic membrane?
Tympanic cavity proper
The eustachian tube connects what two structures? What is the consequence of this?
Middle ear to the nasopharynx
Bacteria/ viruses from pharynx/ tonsils can spread to the middle ear
Why can tonsillitis/ pharyngitis mimic earache?
They have a common sensory nerve supply: CNIX
What structure marks the opening of the Eustachian tube?
Pharyngeal tonsil ‘adenoid’
Outline the nerve supply to the naso-,oro- and laryngopharynx respectively?
Naso- and oropharynx = CNIX
Laryngopharynx = CNX
What is the aditus? What is the consequence of this?
Doorway from the epitympanic recess to the mastoid antrum
Mastoiditis (spread of infection from middle ear cavity)
State the structures that form the two main bony prominences of the middle ear
Left promontory: Left SCC of internal ear
Right promontory: Medial wall of the cochlea
What base of skull foramen does CNVII drain into?
IAM –> Facial canal –> Stylomastoid foramen
What is the CNS connection of CNVII?
Pontomedullary junction
Outline the intracranial course of CNVII
Chorda tympani supplies taste to the anterior 2/3s of the tongue and parasympathetic to submandibular and sublingual glands
Motor innervation to stapedius
What is the function of stapedius?
Reduces stapes movement to protect internal ear from excessive noise
Outline the extracranial course of CNVII
Chorda tympani contributes to lingual branch of CNV3
Muscles of facial expression
PS axons to submandibular and sublingual glands
List the muscles of facial expression
Elevators of lips
Frontalis
Orbicularis oris
Orbicularis oculi
What is the origin and insertion of the muscles of facial expression?
Bone
Superficial fascia
What is the function of the muscles of facial expression?
Pull on skin when contracted
How do you test the muscles of facial expression?
Ask the patient to frown, close eyes tightly, smile, puff out cheeks against resistance
What is the clinical term for the line between the lips and skin proper?
Vermillion border
A sunken buccal fat pad is a sign of…
Malnutrition
Outline the innervation of the middle ear, be specific
CNVIII Cochlear nerve (hearing) Vestibular nerve (balance)
The labyrinths of the ear are found within…
Otic capsule
The bony labyrinths themselves contain what type of fluid?
Perilymph
What is located within the bony labryinth? What fluid can be found within this structure?
Membranous labyrinths of cochlea and SCC
Endolymph
What imaging is used to view the internal ear?
MRI
Outline the six stages of sound transmission to the internal ear
- Sound waves cause the TM to vibrate
- Waves pass to the ossicles
- Waves pass to the base of the stapes in the oval window
- Vibration of stapes forms pressure waves in perilymph
- Hair cells in cochlea move causing neurotransmitter release and APs firing to the brain via the cochlear nerve
- APs descend and produce vibrations that are dampened at the round window
List symptoms associated with IAM pathology
DAMAGE TO CNVII
Ipsilateral reduced facial expression, taste and salvations, sense in auricle
DAMAGE TO CNVIII
Ipsilateral reduced hearing and balance