Ear Anatomy Flashcards
The temporal bone contains what organs?
Organs of hearing and balance
What nerves are contained in the temporal bone?
Facial (CNVII) and vestibulocochlear (CNVIII)
What type of nerves are CNVII and CNVIII?
Special sensory
What is the pterion?
An H shaped suture which is the thinnest part of the skull
The sutures of what bones form the pterion?
Frontal, parietal, temporal and sphenoid
What bones form the anterior cranial fossa?
Frontal, ethmoid and sphenoid
What bones form the middle cranial fossa?
Sphenoid and temporal
What bones form the posterior cranial fossa?
Temporal and occipital
What is the only base of skull foramina in the anterior cranial fossa?
Cribiform plate of ethmoid bone
What cranial nerve passes through the cribiform plate of ethmoid bone?
CNI
Name the 5 foraminae from anterior to posterior in the middle cranial fossa?
Optic canal, superior orbital fissure, foramen rotunda, foramen ovale, intracranial opening of the carotid canal
What cranial nerve passes through the optic canal?
CNII
What cranial nerves passes through the superior orbital fissure?
CNIII, CNIV, CNV1 and CNVI
What cranial nerve passes through the foramen rotundum?
CNV2
What cranial nerve passes through the foramen ovale?
CNV3
What base of skull foraminae are found in the posterior cranial fossa?
Internal acoustic meatus, jugular foramen, hypoglossal canal
What cranial nerves pass through the internal acoustic meatus?
CNVII and CNVIII
What cranial nerves pass through the jugular foramen? What other structure passes through?
CNIX, CNX, CNXI / internal jugular vein
What cranial nerve passes through the hypoglossal canal?
CNXII
What parts make up the external ear?
Auricle to tympanic membrane via the external acoustic meatus
What is the function of the external ear?
Collects and conveys sound waves to the tympanic membrane
What parts make up the middle ear?
Tympanic membrane to the oval window and also eustachion tube
What is the function of the middle ear?
Amplifies and conducts sound waves to the internal ear
What parts make up the inner ear?
Oval window to the internal acoustic meatus
What is the function of the inner ear?
Converts special sensory information into fluid waves, then APs and then conducts these to the brain
What is the sensory supply to the superior parts of the external acoustic meatus and most of the tympanic membrane?
CNV3
What is the sensory supply to the inferior parts of the external acoustic meatus and tympanic membrane?
CNX
What is the sensory nerve supply to the helix of the ear?
C2, 3 spinal nerves
What is the sensory nerve supply to the middle of the external ear?
CNVII
Where does the lateral surface of the superior half of the auricle drain to?
Parotid nodes
Where does the cranial surface of the superior half of the auricle drain to?
Mastoid nodes and deep cervical nodes
Where does the rest of the auricle including the lobe drain to?
Superficial cervical nodes
Where does all lymph from the ear ossicle eventually drain?
Deep cervical nodes, thoracic/right lymphatic duct, venous angle
What makes up the skeleton of the external ear?
Temporal bone and elastic cartilage
What structure runs the length of the ear canal?
External acoustic meatus
Is the ear canal more bony or cartilage?
1/3rd cartilage, 2/3rds bone
What do ceruminous glands do?
Produce earwax
In a child, the EAM is short and straight. What way should you pull the ear for examination?
Posteroinferiorly
In an adult, the EAM is curved. What way should you pull the ear for examination?
Posterosuperiorly
What is the pars flaccida?
A thin part of the tympanic membrane (superior)
What is the pars tensa?
A thick part of the tympanic membrane (posterior)
What is the umbo?
Most inwardly depressed part of the tympanic membrane
What nerve supplies general sensory supply to most of the external surface of the tympanic membrane?
CNV3- auriculotemporal branch
What nerve supplies general sensory supply to most of the internal surface of the tympanic membrane?
CNIX
Where does the glossopharyngeal nerve supply sensory innervation to?
Middle ear cavity, Eustachian tube, nasopharynx, oropharynx and tonsils
What is the function of the Eustachian tube?
Connects the tympanic cavity to the lateral wall of the nasopharynx
What are the 3 auditory ossicles of the middle ear? How do these articulate?
Malleus, incus and stapes- articulate via synovial joints
The base of the stapes bone fits into where?
Oval window
What is the sensory nerve supply to the Eustachian tube? Pain here can sometimes be caused by what?
CNIX- tonsillitis or pharyngitis (referred pain)
What type of supply can the facial nerve give?
Special sensory, sensory, motor and parasympathetic
Where does the facial nerve connect to the CNS?
The brainstem at the junction between the pons and medulla
Where does the facial nerve go after the internal acoustic meatus?
The facial canal of the petrous temporal bone
What does the facial canal connect?
The internal acoustic meatus to the stylomastoid foramen
What does the chorda tympani branch of CNVII do?
Supplies the tastebuds of the anterior tongue and parasympathetic supply to the submandibular and sublingual glands
CNVII can be clinically tested by asking the patient to do what?
Frown, close eyes tightly, smile and puff out cheeks
What happens to the buccal fat pad in illness?
It is lost- giving the appearance of sunken cheeks (a clinical sign of malnutrition)
What is the area of the face where lacerations must be very carefully sutured by a specialist?
Vermillion border of the lips
What are the two parts of CNVIII and what are their functions?
The cochlear nerve (hearing), the vestibular nerve (balance)
Where does the otic capsule sit?
The temporal bone
The otic capsule contains what?
Bony labyrinth- fluid filled spaces
What is found within the perilymph (fluid) of the bony labyrinth?
Membranous labyrinth, communicating sacs and ducts with endolymph fluid
What are the cochlear and semicircular ducts filled with?
Endolymph
APs from the cochlear duct are sent to the brain via what nerve?
Cochlear nerve
APs from the semicircular duct are sent to the brain via what nerve?
Vestibular nerve
Complete the following.
Sound waves make (1) vibrate. These vibrations are transmitted through (2). Base of stapes vibrates in (3) and the vibration of stapes created pressure waves in (4). Hair cells in the cochlea are moved, neurotransmitter is released, APs are stimulated and conveyed to the brain by (5). Pressure waves descend and become vibrations again. Pressure waves are dampened at the (6).
1 = tympanic membrane, 2 = ossicles, 3 = oval window, 4 = perilymph, 5 = cochlear nerve, 6 = round window
Where does CNVIII connect with the CNS?
At the brainstem at the junction between pons and medulla