Anatomy And Histology Of The Ear Flashcards
What does the external ear consist of?
Auricle to the tympanic membrane
What are the functions of the external ear?
Catches sound waves and directs them to EAM
EAM transmits sound waves to tympanic membrane
Spot to check an indiv. Temp.
What is the gold standard for checking an individual’s temperature and what is secondary to ti?
Rectal; external ear
What does the middle ear consist of?
Tympanic membrane to oval window
What are the functions of the middle ear?
Take sound waves from ext. and turn them into physical movement
Pressure equalization by pharyngotympanic tube
How do sound waves move in the middle ear?
Ext ear to physical movement; moving tympanic membrane to malleus to incus to stapes which then pushes on oval window
What changes the pressure of the middle ear?
Volume of the middle ear
Tympanic membrane can bulge out
Tensor tympani contracts o relaxes
Fluids go in and out
What does the inner ear consist of?
Oval window to internal acoustic meatus
What is the function of the inner ear?
Balance
Takes external sound waves and transforms them into usable info for the brain
What are the efferent and afferent nerve fibers during the cough reflex?
Efferent: vagus n. And phrenic n.
Afferent: glossopharyngeal n.
what innervated the superior portion of the EAM?
CN 7
What innervates the posterior portion of the EAM?
Great auricular n. (C3, 4)
What innervates the anterior portion of the EAM?
CN V3- Auriculotemporal n.
What innervates the inferior portion of the EAM?
CN X (Arnold N.)
How long is the canal leading to the tympanic membrane?
How is it shaped?
2-3 cm
Lateral 1/3 = s-shaped
Where and what are the glands of the ear?
Ceremonious glands = make wax
Sebaceous glands
In Integument
What comprises the outer 2/3s of the EAM?
Soft connective tissue and cartilage
What comprises the inner 1/3 of EAM?
What is the CT of this portion? Why is this clinically relevant?
Skin and bone
**Only place in the body where skin, periosteum and bone exist directly on top of each other
NO CT = bleeds easily
What bone is the middle ear located in?
Petrous portion of temporal bone
What are the two parts to the middle ear?
Tympanic cavity proper (aka mesotympanum)
Epitympanic recess
What are the boundaries of the middle ear?
Roof: tegmental wall
floor: jugular wall
Lateral wall: membranous wall
Medial wall: labyrinthine wall
Posterior wall: mastoid
Anterior wall: carotid wall
What are the 3 special features we can see in the middle ear?
Lateral semicircular canal
Facial n.
Labyrinth wall
What innervates the helix and depression of the external ear?
Facial N.
What innervates the lobule of the external ear and right behind the lobule?
Lesser occiptal n.
Greater auricular n.
What innervates the skin of the face anterior to the external ear?
Auriculotemporal (V3)
What innervates the concha of the external ear?
Vagus n. And Glossopharyngeal n.
What innervates the mastoid process and back of ear lobe?
Facial n.
What is the tympanic membrane?
Semi-transparent membrane ~1 cm in diameter
Histologically, what is the outer layer and what is the inner layer?
Outer: stratified squamous epithelium
Inner: simple cuboidal epithelium
What is the umbo?
Concavity in the tympanic membrane, creating a cone shaped projection oriented toward the EAM
What is the function of the tympanic membrane?
Moves with sound and transmits it to the ossicles
What is the external innervation of the tympanic membrane?
Auriculotemporal -V3
Also CN 6, 10
What is the internal innervation of the tympanic membrane?
CN V3
CN 10, 9
What are the auditory ossicles?
Malleus, incus, stapes
What is the function of the ossicles?
They bridge the tympanic membrane w/ the oval window of the cochlea
What is the short process of the incus connected to?
Posterior wall
What does the base of the stapes vibrate?
The oval window
What is the O, I, A and N of the Tensor Tympani M. ?
O: pharyngotympanic tube, greater sphenoid wing, petrous part of temporal bone
I: handle of malleolus
N: CN V3
A: pulls on handle of malleolus to tense membrane and reduce amplitude
What is the O, I, A and N of the Stapedius M.?
O: within pyramidal eminence
I: stapes
N: CN 7
A: pulls stapes posteriorly, tightening annular L attaching it to the oval window; reduces oscillatory tangle and prevents excess movement of stapes thereby dampening loud sounds
What is the blood supply to the external ear?
Posterior auricular a.
Superficial temporal a.
Anterior auricular As.
Where is the Pharyngotympanic tube?
In the middle ear connecting the tympanic cavity with the nasopharynx
What makes up the distal 2/3 of the Pharyngotympanic tube?
Proximal 1/3?
2/3: Boney
1/3 : Cartilage
(Distal 2/3 EAM- cartilage)
(Proximal 1/3 EAM - boney)
What is the function of the pharyngotympanic tube?
What sensation do we often associate with the PT Tube?
Equalize pressure
Ear popping sensation
What are the muscles that expand the PT Tube?
Levator Veli M.
Tensor Veli Palatini.
How does Levator Veli palatini interact with the PT Tube?
Contracts longitudinally which pushes against one wall of the PT Tube
How does the Tensor Veli Palatini M. Interact with the PT Tube?
Pulls on other wall of PT Tube
levator pushes the other