What does the ear consist of?
- external ear
- middle ear (tympanic cavity)
- internal ear, or labyrinth, which contains the organs of hearing and balance
What does the external ear consist of?
The auricle or pinna, and the external auditory meatus
Auricle
- Has a characteristic shape that allows it to collect air vibrations
- consists of a thin plate of elastic cartilage covered by skin
What kind of muscles does the auricle have?
Both intrinsic and extrinsic muscles that are innervated by the facial nerve
External auditory meatus
-curved tube that leads from the auricle to the tympanic membrane and conducts sound waves to the tympanic membrane
Outer third of the meatus
Composed of cartilage
Inner two thirds of external auditory meatus
Bone
Sensory nerve supplying the lining of the meatus
- auriculotemporal nerve
- auricular branche of the vagus nerve (CN X) ***
Lymph drainage of the external auditory meatus
Superficial parotid, mastoid, and superficial cervical lymph nodes ***
What is at the end of the external auditory meatus
Tympanic membrane
Tympanic membrane examination
- external auditory meatus must be pulled upward and backward for adults
- tympanic membrane is pearly gray and concave
What is the depression in the center of the tympanic membrane called
Umbo
What is the middle ear
An air filled cavity in the petrous portion of the temporal bone ***
What is the middle ear lined with and what does it contain
Mucous membranes and auditory ossicles
Middle ear communicates with what
In front of the nasopharynx via the auditory tube and behind with the mastoid antrum ***
Roof of middle ear (tympanic cavity)
Tegman tympani, a thin plate of bone, which is part of the petrous temporal bone; separates the tympanic cavity from the temporal lobe nd its meninges
Floor of the middle ear (tympanic cavity)
Thin plate of bone that separates the tympanic cavity from the superior bulb of the internal jugular veins
Anterior wall of the middle ear (tympanic cavity)
Thin plate of bone with two openings, one for the auditory tube and one of the tube of the tensor tympani
Posterior wall of middle ear (tympanic cavity)
Bone with an opening called the aditus to the mastoid antrum, and a small, conical projection called the pyramid
Medial wall of the middle ear (tympanic cavity)
Lateral wall of the inner ear, which has a rounded projection called the promontory, caused by the underlying cochlea; above and behind the promontory is the fenestra vestibuli (oval window); below and behind the promontory is the fenestra cochleae (round window)
Lateral wall of the middle ear
Formed by the tympanic membrane, which is obliquely placed, it is concave laterally
What are the auditory ossicles
Malleus, incus, stapes
What is the largest ossicle
Malleus
Process of malleus
Called the handle
Attached to the medial surface of the tympanic membrane
What does the malleus articulate with?
Incus
What does the incus articulate with?
Stapes
Where does the footplate or base of the stapes fit into?
Fenestra vestibuli (oval window)
What are the two muscles associated with the ossicles
The tensor tympani and the stapedius
Where does the tensor tympani originate
In the wall of the auditory tube and its own canal ***
Where does the tensor tympani insert?
Handle of the malleus
Innervation of the tensor tympani
Form branch of V3
Action of tensor tympani
Dampen vibrations of the tympanic membrane
Where does the stapedius originate
From the pyramid on the posterior wall of the middle ear
Where does the stapedius insert
On the neck of the stapes
Innervation of the stapedius
From branch of the facial nerve
Action of the stapedius
Dampen the vibrations of the stapes
What does the auditory tube connect?
Anterior wall of the tympanic cavity to the nasopharynx
Posterior part of auditory tube
1/3 bony
Anterior 2/3 part of the auditory tube
Cartilagenous
Where does the auditory tube pass?
Over the upper border of the superior constrictor **
What is the function of the auditory tube?
Equalize pressure in the middle ear with atmospheric pressure ***
Where does the mastoid antrum lie
Behind the middle ear in the petrous portion of the temporal bone
What does the mastoid antrum communicate with?
Inferiorly with the mastoid air cells
Mastoid air cells
Series of communicating cavatives within the mastoid process that are continuous with the antrum and middle ear
What are the mastoid air cells lined with?
Mucous membrane
Where do microbes that cause infection enter the ear?
Auditory tube
When the facial nerve reaches_________, it enters__________
- bottom of the internal auditory meatus
- facial canal
How ones the facial nerve tun around the vestibule?
Laterally above the vestibule of the inner ear until it reaches the medial wall of the middle ear
After the facial nerve reaches the medial wall of the middle ear, what happens?
Expands to form the geniculate ganglion
After facial nerve forms the geniculate ganglion…
The nerve bends sharply backwards above the promontory
When the facial nerve arrives at the posterior wall of the middle ear…
It curves downward on the medial side of he aditus of the mastoid antrum
What gives a branch to the stapedius muscles and where?
The facial nerve descends in the posterior wall of the middle ear, behind the pyramid, where it gives this branch
What is the bend of the facial nerve called?
Genu
Where does the facial nerve emerge?
Stylomastoid foramen
Chroda tympani
Arises form the facial nerve just above the stylomastoid foramen
Where does the chorda tympani enter the middle ear?
Close to the border of the tympanic membrane and crosses the handle of the malleus
Where does the chorda tympani exit the middle ear?
Through the petrotympanic fissure to enter the infratemporal fossa to join the lingual nerve
What kind of fibers does the chorda tympani contain?
Taste fibers to the anterior 2/3 of the tongue, and preganglionic parasympathetic fibers destined for the submandibular ganglion
What is the tympanic nerve a branch of?
Glossopharyngeal nerve
Where does the tympanic nerve branch from CN IX?
Just below the jugular foramen
How does the tympanic nerve pass
Through the floor of the middle ear and onto the promontory where it splits into branches forming the tympanic plexus
What does the tympanic plexus supply?
The mucosa of the middle ear
What branch does the tympanic plexus give off?
The lesser petrosal nerve
What kind of fibers does the lesser petrosal nerve contain?
Preganglionic parasympathetic fibers destined for the otic ganglion ***
Where does the lesser petrosal nerve exit the middle ear?
Through a small canaliculus in the roof
Where does the lesser petrosal nerve exit the skull
Through the foramen ovale and joins the otic ganglion
