Anatomy & Histology of Ear Flashcards
This portion of the ear is from the Auricle to the Tympanic Membrane.
External ear
This portion of the ear is from the Tympanic Membrane to the Oval Window.
Middle ear
This portion of the ear is from the Oval Window to the Internal Acoustic Meatus.
Inner ear
This part of the external ear is made of non-cartilaginous CT.
Lobule (Ear lobe)
What provides blood supply to the external ear?
External Carotid A. via the Posterior Auricular A. and Superficial Temporal A.
What innervates the posterior external ear?
Lesser Occipital N. (from Cervical Plexus)
Greater Auricular N. (from Cervical Plexus)
What innervates the anterior external ear?
Auriculotemporal N. (from CN V)
***Runs with Superficial Temporal A. (from ECA)
What innervates the central area of the external ear?
Vagus N. (CN X)
Glossopharyngeal N. (CN IX)
This nerve provides sporadic innervation to the external ear. Some in the central area, some in the back near the mastoid.
Facial N. (CN VII)
This is the canal leading to the Tympanic Membrane (2-3 cm). The lateral third is S-shaped and it contains ceruminous glands (make wax) and sebaceous glands. Cartilage is beneath fibrous CT.
External auditory canal (meatus)
The area in the external ear (central, inferior) that is innervated by the Vagus N. (also called the _______ N.). This causes the cough reflex to occur.
Arnold
What is the outer 2/3 of the External Acoustic Meatus made of?
CT and Elastic cartilage
What is the inner 1/3 of the External Acoustic Meatus made of?
Skin and bone
This is the only place in the entire body where skin, periosteum, and bone exist directly on top of each other. There is no CT, therefore it bleeds easily.
Inner 1/3 of External Acoustic Meatus
What type of epithelium is the External Acoustic Meatus made of?
Keratinized Stratified Squamous Epithelium
***Also has hair follicles, ceruminous glands, and sebaceous glands
This is a semi-transparent membrane that is approximately 1 cm in diameter. It is connected to the handle of the Malleus, which gives it concavity making it cone-shaped. The cone is oriented toward the External Auditory Meatus.
Tympanic Membrane
The Tympanic Membrane has an outside layer and inside layer. What type of epithelium are each of these made of?
Outer layer – Stratified squamous epithelium
Inner layer – Simple cuboidal epithelium
What is the time of the cone of the Tympanic Membrane called?
Umbo
The Tympanic Membrane has a flaccid part and a tense part. It moves with sound and transmits to the _________.
Ossicles
What is important to see in the 2nd quadrant of the Tympanic Membrane?
Cone of light
The Tympanic Cavity (middle ear) is located in the petrous portion of the Temporal bone. It contains two parts, which are…
Tympanic Cavity Proper (called Mesotympanum)
Epitympanic Recess
What make up the “walls” of the Tympanic Cavity?
Tegmental Wall (roof) Jugular Wall (floor) Membranous Wall (lateral) Labyrinthine Wall (medial) Mastoid Wall (posterior)
This nerve pierces through the Jugular Wall, the “floor” of the Tympanic Cavity.
Tympanic N.
The Tympanic N. meets with the Lesser Petrosal N. within the…
Tympanic Plexus
This muscle is attached to the Malleus.
Tensor Tympani M.
This nerve passes over the Tensor Tympani M.
Chorda Tympani (from Facial N.)
The Malleus connects to the ________, and this attaches to the _________, which attaches to the Oval Window.
Incus
Stapes
This muscle attaches to the Stapes and the Mastoid.
Stapedius M.
What are the three prominences within the middle ear?
Lateral Semicircular Canal
Facial N.
Labyrinth Wall (promontory)
This connects the Tympanic Cavity (middle ear) with the Nasopharynx (back of the throat).
Pharyngotympanic Tube (Eustachian Tube)
The proximal part of the Pharyngotympanic Tube is (BONE/CARTILAGE) but the distal remainder is (BONE/CARTILAGE).
Bone
Cartilage
- **Opposite pattern as External Acoustic Meatus
- **EAM – distal 2/3 cartilage, proximal 1/3 bony
- **PT – distal 2/3 bony, proximal 1/3 cartilage
What is the function of the Pharyngotympanic Tube?
Equalize pressure (gives ear popping sensation)
This muscle expands the Pharyngotympanic Tube. It contracts longitudinally which PUSHES against one wall.
Levator Veli Palatini
This muscle expands the Pharyngotympanic Tube. It PULLS on one wall (the other wall is being pushed by the other muscle).
Tensor Veli Palatini
The Pharyngotympanic Tube is _______ cartilage covered by integument.
Elastic
What type of epithelium is the Pharyngotympanic Tube composed of?
Pseudostratified Epithelium
***Different from External Acoustic Meatus, which is Keratinized Stratified Squamous Epithelium
What are the auditory ossicles?
Malleus
Incus
Stapes
The auditory ossicles bridge the Tympanic Membrane with the Round Window of the Cochlea.
False. The auditory ossicles bridge the Tympanic Membrane with the Oval Window of the Cochlea.
What are the parts of the Malleus?
Head
Neck
Handle
What are the parts of the Incus?
Body
Short Process
Long Process
The short process of the Incus is connected to what?
Mastoid (Posterior) wall
The handle of the Malleus is connected to what?
Tympanic Membrane
What are the parts of the Stapes?
Head
Limbs
Base (Footplate)
This component of the Stapes is what vibrates the Oval Window.
Base (Footplate)
The auditory ossicles amplify the force on the Tympanic Membrane by how much?
10x
The auditory take sound waves, create physical energy and transfer it to the…
Oval Window
This muscle originates on the surface of the Pharyngotympanic Tube, Greater Wing of Sphenoid, and petrous part of Temporal bone. It inserts on the handle of the Malleus.
Tensor Tympani
This muscles pulls on the handle of the Malleus to tense the membrane and reduce amplitude.
Tensor Tympani
What innervates the Tensor Tympani?
CN V (Trigeminal)
This muscle originates within the Pyramidal Eminence (hollow cone-shaped eminence on posterior wall of Tympanic Cavity). Its tendon exits via a small pinhole size foramen and inserts onto the Stapes.
Stapedius
This muscle pulls on the Stapes posteriorly and tightens the annular ligament attaching it to the Oval Window. This reduces oscillatory range and prevents excessive movement of the Stapes.
Stapedius
What innervates the Stapedius?
CN VII (Facial)
The bony labyrinth is a cavity within the petrous region of the Temporal bone. It is lined with (PERIOSTEUM/ENDOSTEUM) and is separated from the membranous labyrinth by (PERILYMPH/ENDOLYMPH).
Endosteum
Perilymph
This is made of small sacs and tubes within the bony labyrinth. It forms a continuous space enclosed within epithelium. Contains sensory cells.
Membranous Labyrinth
There are two parts of the Membranous Labyrinth that perform different jobs, what are these?
Cochlear Duct – hearing
Utricle, Saccule, Semicircular Ducts – balance
What is the Membranous Labyrinth filled with?
Endolymph
The bony labyrinth has (DUCTS/CANALS) while the membranous labyrinth has (DUCTS/CANALS).
Canals
Ducts
These cells are only present in the Membranous Labyrinth, and are sensory.
Hair cells
Each hair cells has multiple ________ and one ________.
Stereocilia
Kinocilium
The Cochlear Duct divides the canal into 3 parallel soft tissue-lined compartments. These are…
Scala Vestibuli
Scala Media
Scala Tympani
Which parts of the Cochlear Duct contain perilymph or endolymph?
Scala Vestibuli – Perilymph
Scala Media – Endolymph
Scala Tympani – Perilymph
This is what separates the Scala Vestibuli and the Scala Media.
Vestibular (Reissner’s) Membrane
This is the spiral space within bone that contains the Cochlear Duct.
Cochlear Canal
This part of the Cochlear Duct contains perilymph that is moved by the Stapes at the Oval Window. It is continuous with the Scala Tympani.
Scala Vestibuli
This part of the Cochlear Duct is the middle compartment and contains endolymph.
Scala Media
This is part of the lateral wall of the Scala Media, and produces endolymph.
Stria Vascularis
This part of the Cochlear Duct is connected to the Round Window.
Scala Tympani
This on the floor of the Scala Media resting on the Basilar Membrane.
Organ of Corti
This is the inner spiraling bony shelf serving as support for the Tectorial Membrane and Spiral Ganglia.
Outer Spiral Lamina (OSL)
What is the Organ of Corti composed of?
Hair cells (sensory)
Inner and Outer Phalangeal cells (support for hair cells)
Pillar cells (support between Basilar Membrane and Tympanic lip)
In the Organ of Corti, there are ______ row(s) of outer hair cells and ______ row(s) of inner hair cells.
Three
One
In the Organ of Corti, hair cell _________ are embedded in the overlying Tectorial Membrane extending from the OSL (Outer Spiral Lamina).
Stereocilia
The Basilar Membrane vibrates with sound, causing deflection of stereocilia attached to the Tectorial Membrane. This opens the ______ channels in hair cells.
K+
Bipolar neuron cell bodies are located in the Spiral Ganglion within the…
Modiolus (Central Axis)
The external ear catches sound waves and directs (and concentrates) them to the External Acoustic Meatus. The External Acoustic Meatus then continues transmitting the sound waves to the…
Tympanic Membrane
The external ear also serves as a spot to check an individuals _________. It is almost as accurate as checking rectally, which is commonly referred to as gold standard.
Temperature
The middle ear takes the sound waves (concentrated and directed by the external ear) and turns it into physical movement. Describe the path of the movement.
Sound waves move the Tympanic Membrane, moves the Malleus, moves the Incus, moves the Stapes, which pushes on the Oval Window.
The pressure in the middle ear is equalized by the _________ ________.
Pharyngotympanic Tube
The inner ear is responsible for taking external sound waves and transforming them into what?
Usable information for the brain
The inner ear is also responsible for ________.
Balance
In the inner ear, the Stapes moves the Oval Window causing fluid pressure wave formation in _________. This wave distorts the Vestibular Membrane causing a pressure wave within ________ of the Scala Media. This then displaces the Basilar Membrane and distorts ________ of hair cells. Pressure in ________ is transferred to Scala Tympani and exits via the round window (another reason Pharyngotympanic Tube is important).
Perilymph
Endolymph
Stereocilia
Perilymph
The Semicircular Canals are three canals in three different axes. They are…
Anterior Semicircular Canal = Forward rotation (Sagittal Plane)
Posterior Semicircular Canal = Lateral rotation (Coronal Plane)
Horizontal Semicircular Canal = Transverse rotation (Transverse Plane)
The Semicircular canals are filled with ________ and connected to the _______.
Endolymph
Utricle
The end of the Semicircular Canals have ampulla with a gelatinous-like cap called a ________. This is displaced by fluid motion within the canal.
Cupulla
T/F. Semicircular Canals serve as sensors of rotational velocity.
True
The Vestibule contains the ________ and ________.
Saccule
Utricle
The Saccule and Utricle each contain a ________ which is comprised of a cluster of hair cells with stereocilia with overlying gelatinous material called Otolithic Membrane.
Macula
The Otolithic Membrane (covering Macula) is covered with calcium carbonate/protein crystals called ________.
Otoconia
The Saccule and Utricle serve as sensors for what?
Gravity
Linear acceleration
This recognizes linear acceleration and head tilts in the horizontal plane.
Utricle
***Tells us which way is forward
This recognizes linear acceleration and head tilts in the vertical plane.
Saccule
***Tells us which way is up (how you know if you’re upside down)
Semicircular canals use the ________ to move hair cells, while the Utricle and Saccule use _______ to move their hair cells.
Cupulla
Otoliths
The surface of hair cells contains rows of stereocilia called sensory hairs that increase in height in a particular direction. The vestibular system contains one true cilia located behind the tallest stereocilia, called the…
Kinocilium
Stereocilia are stiff and contain mechanoelectric gated ion channels. If deflected toward Kinocilium, then the K+ channels (CLOSE/OPEN). If deflected away from the Kinocilium then the K+ channels will (CLOSE/OPEN).
Open
Close
Hair cells are innervated by…
Afferent and efferent nerves
Why do you have to be careful with certain antibiotics concerning the ear?
They can damage the hair cells, and hair cells cannot be regenerated.
This is between the bony labyrinth and the membranous labyrinth. Its composition is similar to CSF.
Perilymph
Perilymph originates from _________ (around bone).
Periosteum
Perilymph drains via the Perilymphatic Duct (Cochlear Aqueduct) into the…
Subarachnoid Space
This is within the membranous labyrinth and is high in K+ and low in Na+. It originates in the Stria Vascularis.
Endolymph
Endolymph drains via the Endolymphatic Duct into the venous sinuses of the…
Dura Mater
This is caused by an infection of mastoid cells (of temporal bone). It can spread into cranial fossa via the petrosquamous cranial suture. Treated with antibiotics.
Mastoiditis
This is often damaged due to medial ear pressure because of fluid or barotrauma. It an also occur from external trauma (shoving something into your ear). Most heal but need follow up perhaps with antibiotics.
Tympanic Membrane
This antibiotic should be avoided because it can damage the inner ear (hair cells).
Gentamicin
This is an ear ache with possible fluid or pus in the middle ear due to inflammation or infection. The Tympanic Membrane appears red and bulged and fluid may be visible through it. If left untreated, it can impair hearing and scar the auditory ossicles.
Otitis Media
***VERY common – number one reason for hospital visits (affects 11 percent of worlds population)
This is when you experience dizziness, vertigo, high-pitched rushing or roaring sound (tinnitus) and fluctuating hearing loss. It is associated with an increase in endolymph volume leading to abnormal signaling. The cause is unclear and mild cases can be treated with medication. Severe cases require surgical ablation of parts of labyrinthine system but risks permanent hearing loss.
Meniere’s Syndrome
This has similar symptoms to Meniere’s Syndrome, but is less severe and usually resolves within a week.
Viral Labyrinthitis
This type of hearing loss affects the outer and middle ear from fluid build up, otitis, excessive wax, or otosclerosis.
Conductive hearing loss
This type of hearing loss is a reduction in sound level and/or fidelity due to damage to the inner ear or auditory nerve. It affects hearing at different frequencies and intensities. Often age-related and noise induced.
Sensorineural hearing loss
This type of hearing loss is from a problem in the CNS.
Central hearing loss
What are causes of hearing loss?
Aging Illness Medications Genetics Noise Ear infection Physical trauma Alchohol or tobacco
Why do 8/10 children suffer from Otitis Media before 10 years of age?
The angle of Pharyngotympanic Tube is more shallow in children, therefore allows less drainage and pressure equalization of the inner ear. This heightens risk of infection and can cause pain or an ear ache.
The auricle of the ear is made from elastic cartilage and is supplied with blood and nutrients by the perichondrium. What happens if the perichondrium is sheared off the elastic cartilage?
Can develop a hematoma or necrotic cartilage
If the perichondrium is sheared from the elastic cartilage (of auricle) it can result in necrotic cartilage. What will the necrotic cartilage result in?
Chondrogenesis (aka new cartilage growth)
***Common in wrestling – called Cauliflower Ear
