Anatomy-Ear Flashcards
What part of the external ear is responsible for production of ear wax?
The external 1/3 of the external auditory meatus. It contains sweat glands, hair and ceruminous glands. The internal 2/3 is just bone covered by skin.
How do you know if you are looking at the left vs. right tympanic membrane when looking through an otoscope?
Right = cone of light at 5 o’clock. Left = cone of light at 3 o’clock
What structures are indicated below?
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What region of the tympanic membrane is involved in transmitting sound? Why?
Pars tensa. It has a layer of “tense” collagen fibers between the skin and mucosa of the inner ear that can vibrate when sound waves hit it. The pars flaccida is not involved because it only has a layer of skin and mucosa from the inner ear.
You try to do a front flip dive into a swimming pool and turn your head on the way in. Your ear slaps the water and you come up not hearing as well. The doctor says you popped your ear drum. What kind of hearing loss is this?
Conductive. Sound is no longer conducted to the inner ear.
What cavities make up the tympanic cavity?
The epitympanic recess sits above the tympanic membrane. Below that there is the tympanic cavity proper.
What spaces does the middle ear communicate with?
Auditory tube & aditus (leads to antrum and mastoid air cells)
Bone that makes up the roof of the middle ear cavity.
Tegment tympani, thin portion of the petrous temporal bone.
What structure pierces through through the floor of the middle ear cavity?
Tympanic branch of CN IX
How do nasopharyngeal infections spread into the middle ear?
The auditory tube, a perforation in the anterior wall of the middle ear cavity.
What structures perforate through the anterior wall of the middle ear?
Auditory tube, tensor tympani (lying on the cochleariform process) and sympathetic fibers.
What elevation is found on the medial wall of the middle ear cavity? What sits on this elevation?
Promontory. The sympathetic plexus and tympanic branch of CN IX meet at the promontory to form the lesser petrosal nerve.
What openings are found in the medial wall of the middle ear cavity?
Oval window (closed by stapes foot process indicated below), round window (closed by second tympanic membrane)
What structure is located below the prominence of the lateral semicircular canal on the medial wall of the cavity of the middle ear?
CN VII facial canal
What branches does the facial nerve throw to the middle ear cavity before descending through the stylomastoid foramen?
Chorda tympani and nerve to the stapedius (sits on the pyramidal eminence). Note that the facial nerve also gives off the greater petrosal nerve at the geniculate ganglion.
What structure of the skull lies behind to posterior wall of the middle ear cavity?
Sigmoid sinus
What structures are associated with the lateral wall of the middle ear cavity?
Epitympanic recess, tympanic membrane and chorda tympani
Between what two structures does the chorda tympani run?
Malleus (nerve runs medially to it) and Incus (nerve runs laterally to it)
The middle ear cavity is near a lot of important structures. What are more serious complications of a middle ear infection?
Meningitis, temporal lobe abscess, sigmoid sinus thrombosis, mastoiditis, labyrinthitis, ICA/IJV thrombosis and facial nerve palsy.
What are the bones of the middle ear?
The head of the malleus articulates with the body of the incus. The long process of the incus articulates with the neck of the stapes.
What structure in the base of the skull is made by the anterior semicircular canal?
Arcuate eminence.
What are the three parts of the structure seen below?
This is the bony labyrinth of the inner ear. It is made up of 3 semicircular canals, vestibule & cochlea
How many turns of the cochlea are there? What is the 1st turn called?
2.75 turns. The first swoop is the promontory.
What is the structure indicated in pink below? What is important about the area indicated by the arrow?
Bony cochlea surrounded by the petrous temporal bone. The arrow indicates the central bony core (modiolus). It is here where the spiral ganglion sends afferent fibers away that form most of the cochlear nerve.
What structure is indicated in teal below? What are its different parts?
Membranous labyrinth contained within the bony labyrinth. 1) Semicircular ducts 2) Utricle & Saccule 3) Cochlear duct 4) Endolymphatic duct & sac
What structure is contained in the amplified image below?
This is a section from the ampulla of the semicircular duct. This is where the crista ampullaris is located.
Structure that senses angular movements of the head?
Crista ampullaris. Movements of endolymph, move the cupula and in turn move the hair cells.
3 parts of the crista ampullaris
1) Sensory hair cells (type I and II), 2) Supporting cells 3) Cupula (gelatinous membrane)
What structure is indicated by the green arrows below?
Note the type I (chubby) and type II (skinny) mechanoreceptors of the crista ampullaris. These mechanoreceptors have cilia (red) and microvilli (green) on them that are embedded in the cupula.
Type I and type II hair cell sensory innervation
Type I: chalice afferent terminal of vestibular nerve. Type II: Multiple afferent endings of vestibular nerve. Both have synaptice efferent endings from the vestibular nerve.
Function of the specialized epithelium within the utricle and saccule of the vestibule.
Macula: detects gravity (in saccule) and linear acceleration (in utricle).
3 parts of the macula
1) Sensory hair cells 2) Supporting cells 3) Otolithis membrane (contains otoconia)
What are the different regions of the cochlear duct?
1st = scala vestibuli, which starts at the oval window 2) Scala tympani, which starts at the round window.
Identify the organ of Corti in the image below:
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What separates the scala vestibuli and scala tympani from the cochlear duct?
Vestibular membrane (from scala vestibuli) and basilar membrane (from scala tympani)
What structure secretes the endolymph found in the membranous labyrinth?
Stria vascularis. Specialized epithelium in the cochlear duct.
3 parts of the organ of Corti
1) Inner hair cells & Outer hair cells, note that they have no cilium, only stereocilia 2) Inner/outer pillar cells and inner/outer phalangeal cells 3) Tectorial membrane
What cells provide the majority of afferent fibers from the organ of Corti? What is the function of the other cells?
Inner hair cells. The outer cells amplify the mechanical stimulation from the tectorial membrane.
