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101 Cards in this Set
- Front
- Back
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What are the four divisions of the ear?
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Outer
Middle Inner Higher Auditory Pathways (HAP) |
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What is another way to categorize the inner ear?
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Combine the inner ear and the HAP as the entire inner ear
The inner ear is the sensory portion. The HAP is the neural portion. |
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What is a hollow space in the temporal bone?
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the middle ear
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The auricle is helpful in what way?
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Isolating sounds in front of and behind our head
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What are 12 landmarks of the outer ear?
AA CCC DHI LSTT |
antihelix
antitragus concha cavum concha symba crus of helix Darwin's tubercle helix intertragal incisure lobe scaphoid fossa tragus triangular fossa |
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What is another name for Darwin's tubercle?
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auricular tubercle
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The auricle consists of what?
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fibrous cartilage with cutaneous lining
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What is another name for the auricle?
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pinna
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What is another name for the ear lobe?
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earlap
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What are the dimensions of the EAM or ear canal?
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25-35 mm in length
6-8 mm diameter |
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What are the primary functions of the ear canal?
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conduct sound to the eardrum
protective mechanism due to hearing components being located within the bony structures of the head |
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What is the isthmus?
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the junction of the cartilaginous framework and the bony framework of the ear canal
also is a narrowed area |
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What is the consistency of the ear canal?
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the lateral 1/3 to 1/2 is cartilaginous (variable) and the medial 2/3 to 1/2 is osseous (fixed)
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What is another name for earwax?
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cerumen
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The lateral 1/3 of the ear canal contains what?
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hairs or cilia
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What produces earwax?
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cerumen and sebaceous glands
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The ear canal has what shape?
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S-shape
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The pars externa portion of the ear canal moves in what directions?
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medial, anterior, superior
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The pars media portion of the ear canal moves in what directions?
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medial, posterior
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The pars interna portion of the ear canal moves in what direction?
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medial, anterior, inferior
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The ear canal acts like a
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closed-tube resonator
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The ear canal has a resonance peak of
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2500 Hz
intensity level of 17dB |
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The concha has a resonance peak of
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5000 Hz
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The combined resonant frequency of the ear is
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3800 Hz
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What forms the lateral wall of the middle ear cavity?
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the tympanic membrane
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What are the physical characteristics of the TM?
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pearl grey
translucent concave weighs 14 mgs |
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The TM sits in the ear canal at what angles?
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140° superiorly
40° inferiorly (It looks top heavy) \ |
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What is the annulus?
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the fibrocartilaginous ring that is the thickened periphery of the TM
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What is the tympanic sulcus?
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a groove in the bony wall of the meatus within which the annulus rests and holds the TM in place
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The opening at the top of the tympanic sulcus is called the
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notch of Rivinus and is spanned by the pars flaccida (Schrapnell's membrane)
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What properties of the TM make it effective for sound absorption?
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compliance
cone shape small mass |
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What are the three layers comprising the TM?
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EAM side: cutaneous layer
Middle: fibrous layer Tympanic cavity: serous (mucous) membrane |
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What is the fibrous inner layer of the TM comprised of?
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a lateral layer with radial fibers extending from the center
a medial layer with concentric rings more dense at the periphery and the center |
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What are two areas of the TM?
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pars flaccida
pars tensa |
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What is the cone of light?
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the triangular reflection of light seen on the tympanic membrane during examination
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What is the umbo?
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the center of, and thus the most depressed portion of, the TM
also the top of the cone of light the inferior portion of the malleus manubrium reaches to the umbo |
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What are the dimensions of the tympanic cavity?
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15 mm high
15 mm deep (long) 6 mm wide (superior) 2 mm wide (medial) 4 mm wide (inferior) |
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Where is the tympanic cavity located?
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in the petrous portion of the temporal bone
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What portion of the tympanic cavity extends upward beyond the superior border of the TM?
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the epitympanic recess or attic
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What is contained in the epitympanic recess?
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the head of the malleus and most of the incus
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What portion of the tympanic cavity lies medially to the TM?
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the tympanic cavity proper
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How does air enter the tympanic cavity?
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through the auditory tube
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What separates the tympanic cavity from the brain?
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tegmen tympani or the
tegmental wall (paper thin bone) |
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Where is the tympanic aditus located?
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the posterior wall of the epitympanic recess
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The tympanic aditus connects what?
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the tympanic cavity and the tympanic or mastoid antrum
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What are the six walls of the middle ear cavity?
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Tegmental (superior)
Jugular (inferior) Mastoid (posterior) Carotid (anterior) Membranous (lateral) Labyrinthian (medial) |
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What forms a prominence in the jugular (inferior) wall of the middle ear?
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the jugular fossa
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What are the landmarks of the mastoid (posterior) wall of the middle ear? (3)
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fossa incudis
pyramidal eminence tympanic aditus |
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What is the function of the pyramidal eminence?
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contains the stapedius muscle
a tendon exits the apex |
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What is the function of the fossa incudis?
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accommodates the short process of the incus
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What nerve travels horizontally past the malleus and incus?
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the chorda tympani, which is a branch of the facial nerve VII
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What is the function of the chorda tympani nerve?
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carries information from the anterior portion of the tongue to the brain
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What is the cochleariform process?
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an opening in the carotid (anterior) wall into the middle ear allowing the tendon for the tensor tympani muscle to enter
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What two muscles are associated with the middle ear?
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stapedius
tensor tympani |
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What are two landmarks on the carotid (anterior) wall of the middle ear?
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opening for the auditory tube
cochleariform process |
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What are the landmarks for the Labyrinthian (medial) wall? (5)
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oval window (fenestra vestibule)
round window (fenestra rotunda) promontory (basal turn of the cochlea) prominence of the facial nerve canal prominence for lat. semi circular canal |
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What causes the promontory on the labyrinthian (medial) wall of the middle ear?
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the lateral projection of the basal turn of the cochlea
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What are the two purposes of the ossicles?
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deliver sound vibrations to the inner ear fluids
help the inner ear from being overdriven by excessively strong vibrations |
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What are the parts of the malleus? (5)
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Head
Neck Anterior process Lateral process Manubrium |
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What occupies 1/2 of the epitympanic recess?
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the malleus head
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What is the manubrium attached to?
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the middle connective tissue of the TM
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What causes the concave nature of the TM?
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the malleus
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Where does the incus attach to the malleus?
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an articular facet on the posterior surface of the malleus
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Where does the tensor tympani tendon attach to the malleus?
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a bony process where the manubrium meets the neck
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What are the parts of the incus? (4)
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body
short process (horizontal; occupies fossa incudis) long process (vertical and parallel to manubrium) lenticular process |
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Where does the incus articulate with the stapes?
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at the lenticular process at the end of the long process
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What are the parts of the stapes? (6)
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head
neck anterior crura (shorter, thinner, less curved) posterior crura obturator foramen (open space between the crura) footplate |
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What is the triangular space between the crura of the stapes?
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obturator foramen
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What attaches to the head/neck of the stapes?
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the stapedial tendon
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How is the stapes footplate connected to the oval window?
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by an annular ring
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What does the auditory tube do?
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allows communication between the middle ear and nasopharynx
equalizes air pressure allows for fluid drainage |
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What are the four sections of the auditory tube?
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osseous
cartilaginous membranous isthmus |
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What is the length of the osseous portion of the auditory tube?
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12-14 mm in length
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Where is the osseous portion of the auditory tube?
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3 mm above the floor of the middle ear
on the cartoid wall just beneath the septum canalis musculotubarii |
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What are the two muscles involved in auditory tube action?
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levator palatini
tensor palatini |
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How does the auditory tube open?
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the palatini muscles contract and pull the lateral cartilage away from the membranous wall
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Where is the termination of the auditory tube?
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at the pharyngeal ostium, it forms a prominence called the
torus tubarius |
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What are the five ossicular ligaments?
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superior malleolar
lateral malleolar anterior malleolar posterior ligament of the incus annular ligament of the stapes |
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What are the attachments for the superior malleolar ligament?
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head of malleus to the tegmen tympani
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What are the attachments for the lateral malleolar ligament?
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neck of the malleus to the bony wall near the notch of Rivinus
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What are the attachments for the anterior malleolar ligament?
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anterior process to the carotid wall
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What are the attachments for the posterior ligament of the incus?
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tip of the short process to the fossa incudis
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What is the ligament of the stapes?
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the annular ligament surrounds the footplate and holds it in the oval window
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What are the two tympanic muscles?
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tensor tympani (length 25 mm)
stapedius (6 mm) |
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What are three characteristics of the tympanic muscles?
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only the tendon enters the middle ear
pennate (resembles a feather) smallest striated muscles in the body |
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What is the origin, insertion, and innervation of the tensor tympani?
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lies superior and parallel to the auditory tube
origin: cartilaginous portion of the auditory tube just above the bony portion insertion: manubrium of the malleus via the cochleariform process nerve: trigeminal V |
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What results when the tensor tympani contracts?
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malleus is pulled medially and anteriorly
increases the tension of the TM |
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Without the transformer action of the middle ear, we would lose
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30 dB of SPL
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In what manner does the TM vibrate?
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like a solid disc pivoted on an axis
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There is greatest displacement on the TM at the
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umbo
15 times greater displacement than at the periphery |
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Where does the axis of the ossicular chain run?
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anterior malleolar ligament to the
anterior process of the malleus through the short process of the incus to the posterior ligament of the incus |
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The stapes vibrates around an axis located where?
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through the posterior crus
the posterior end is more fixed so the footplate moves as if it is on a hinge like a door |
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When sound intensity increases, how does the stapes vibrate?
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the rotational axis changes to a horizontal one through both crura and the stapes has more of a post/inf back and forth motion
this reduces the fluid displacement in the inner ear acting as a protective mechanism |
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What is the problem with airborne sound interacting with a fluid filled inner ear?
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acoustic resistance or impedance
sound is traveling from one medium with certain density and elasticity to another medium with different density and elasticity |
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How is the problem of impedance overcome?
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transformer action of the middle ear via
lever action of the ossicular chain pressure increase at the stapes due to effective areal ratio |
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What is the main function of the middle ear?
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impedance matching transformer
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What are the effective areas of the TM and the footplate and the resulting ratio?
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55 mm²
3.2 mm² 17:1 |
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The force is the same on the TM and the footplate but the
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pressure at the stapes is increased by the area ratio
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The combined ratio of the lever ratio and the areal ratio is
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22:1 17 (areal) x 1.3 (lever)
which equals 27dB |
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What is the manubrium to the incus long process ratio?
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1.3 : 1
the manubrium is 1.3 times longer than the long process |
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What is the path of the acoustic reflex arc?
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Outer ear
Middle ear Inner ear Auditory (8th) nerve Cochlear nucleus (in brainstem) Superior Olivary complexes (right and left) Facial (7th) nerve Stapedial muscle contraction |
