Tympanic Membrane
The average thickness of the T.M is...
0.74 mm (.003 in)
Describe the lever advantage...
1.3:1; Long distance needs less pressure/force - short distance needs high pressure/force
Describe the areal advantage...
17:1; "Thumb-tack." The T.M. is 17 times larger than the oval window.
(Eustachian tube) Carilaginous portion is __, osseous portion is __?
2/3; 1/3
How long is the eustachian tube?
35 mm
The outer ear collects sound and provides pathway because...
Concha is larger than the T.M. The outer ear acts like a funnel and slightly increases SPL at T.M.
Describe the mastoid process of the temporal bone...
Contains air cells
Describe the pinna...
Covered with skin and composed mostly of cartilage with the exception of the lobe
Decussate
Cross over
Describe ectoderm...
Cutaneous - continuous with the EAM
What passes through the petrous-squamosal suture in children directly to the meninges of the temporal lobe of cortex?
Inflammatory conditions of the middle ear
What is the function of pars tensa?
Inserts into boney groove in the tympanic bone
The densest bone in the body is...
The temporal bone
The facial nerve (VII) innervates what?
Chorda tympani, stapedial muscle, and location behind the medial wall
Describe the opening of the eustachian tube...
"Milking" action - tensor palatini pulling on the side of the eustachian tube, opening the tube
Distal
(Distance) Away from a reference point
What is cholesteatoma?
A middle ear tumor; not cancerous. Could turn into Mastoiditus if pushed back toward the mastoid section of your ear.
The ossicles are held in place by...
A series of ligaments, tendons, and joints
Undulations and differences in cartilage of pinna cause...
A sound shadow as well as antiresonances between 6000-12000Hz.
What is the function of the middle ear?
Acts as an impedance matching device between the air-borne sound waves and the fluids of the inner ear
What structures are located within the posterior wall?
Aditus, pyramidal eminence, posterior iter, jugular wall, and the jugular vein
What is the difference between afferent and efferent?
Afferent - Up, towards; Efferent - Down, away
Pars Flaccida contains what?
All layers of the T.M. EXCEPT the fibrous one
Pars Tensa contains what?
All three layers of the T.M.
Describe an adult's E.T...
Angle: about 40 degrees; Length: about 35 mm; Flaccidity: Little to none
Describe a child's E.T...
Angle: more horizontal; Length: shorter than 35 mm; Flaccidity: very flaccid in children
What is epitympanic recess?
Anything above the eardrum
What is hypotympanium?
Anything below the eardrum
How long is the EAM?
Approx. 2.5 cm (1 in) from entrance of concha to T.M.
The incus consists of what structures?
Articular facet, short process, head, long process, and lenticular process
In adults, the T.M. is...
At a 55 degree angle
EAM terminates where?
At the typmanic membrane
Lateral
Away from the midline
Binaural
Both ears
Bilateral
Both sides
(Resonance of middle ear) Effects of increased mass is...
Downward shift of resonant frequency
What are the three layers of the T.M.?
Ectoderm, Mesoderm, and Endoderm
What structures are located within the medial wall?
Facial nerve, promentory of the lateral semi-circular canal, oval window, promentory of the basal turn of the cochlea, and the round window
Describe mesoderm...
Fibrous - Radial fibers and Concentric Fibers
Describe the zygomatic process of the temporal bone...
Forms the zygomatic arch. Connects with the zygomatic bone.
Coronal plane
Frontal view. Cut body in half between front and back
What causes glomus jugularis?
Glomus bodies can push up through the jugular wall from the jugular vein
The malleus consists of what structures?
Head, lateral process, articular facet, anterior process, neck, and manubrium
The stapes consists of what structures?
Head, neck, anterior crus, posterior crus, annular ligament, footplate, and obturator foramen
What is the function of atrium and where is it located?
Help increase the capacity, which in turn, increases the amount of blood it can hold. Located posterior to the aditus
Describe the squamous portion of the temporal bone...
Helps enclose the cranial cavity
In newborns, the T.M. is...
Horizontal
Posterior
In back
Anterior
In front
Where is cerumen made?
In the sebacious and cerumenous glands of the EAM
Where is the jugular vein located?
Inferior to the jugular wall
If the chorda tympani is damaged, what can happen?
It can change your taste buds
How does the outer ear protect the T.M.?
Its S shape provides a physical protection, cerumen and sweat lubricate the EAM and help expel debris, and hair follicles are tilted to concha to discourage debris from entering
Describe the petrous portion of the temporal bone...
Located at the base of the skull between the sphenoid and the occipital bones. Houses inner ear and internal auditory canal.
Describe the styloid process...
Located on the medial/inferior portion of the temporal bone. Attaches to several pharyngeal muscles
Inferior
Lower or below
The eustachian tube consists of what structures?
Lumen, cartilage, tensor palatini, levator palatini, and the temporal bone
What are the three smallest bones in the body?
Malleus, Incus, and Stapes (aka - Ossicles)
Describe endoderm...
Mucous - continuous with the T.M.
What structures are located within the anterior wall?
Muscular-tubal canal, carotid artery, and the anterior iter.
What is impedance mismatch?
Occurs when you have two mediums of differing impedance's. Occurs between gas (air) and fluid of inner ear.
(Eustachian tube) the osseous portion is usually ___, and the cartilaginous portion is usually ___?
Open; closed
Contralateral
Opposite side
What is impedance?
Opposition to the flow of energy
The make of of the T.M. consists of what structures?
Pars Tensa, Pars Flaccida, Manubrium, Umbo, Annulus, Incus, Cone of Light, and Notch of Rivinus
What is the cone of light?
Part of the T.M. that is perpendicular to the light from the ossiscope. Shiney = Healthy
What is the aditus?
Passage or opening for entrance
The tegmen separates the tympanic cavity from the...
Posterior cranial fossa
What is the function of the eustachian tube?
Pressure equalization and drainage
The EAM is what shape?
S shaped
Unilateral
Same side
What is the function of the manubrium?
Serves as an attachment point
Sagittal plane
Side view. Cut body into right and left parts
The EAM is angled which direction?
Slightly forward
What are sebaceous glands important for?
Sweating
Name the walls of the tympanic cavity...
Tegman, Anterior, Jugular, Posterior, and Medial
The outer ear keeps the T.M at a constant ___ and ___.
Temperature; humidity
The posterior cranial fossa houses the...
Temporal lobe
What muscle secures the pinna to the head?
Temporalis muscle
What two muscles help open the E.T.?
Tensor palatini, and the levator palatini
The trigeminal nerve (V) innervates what?
Tensor tympani
What is very thin and translucent (wax paper like)?
The Tympanic Membrane
What structure is eliptically shaped?
The Tympanic Membrane. -- vertically .9 cm and horizontally .8 cm
The internal auditory canal connects inner ear with what?
The brainstem
Where are hair follicles found in the outer ear portion?
The cartilaginous portion of the ear canal
What muscle is attached to the petrous portion?
The levator palatini
The eustachian tube begins at the tympanic cavity and teminates in...
The nasopharynx
The temporal bone contains...
The outer, middle, and inner ear
The ossicles connect the T.M with what?
The oval window
The temporal bone articulates with...
The parietal, occipital, frontal, and sphenoid bones
What are the two main parts of the outer ear?
The pinna (auricle) and the external auditory meatus (EAM aka ear canal)
What is the function of the outer ear?
To collect sound and provide pathways, protect the T.M., keep a constant temperature, help us localize on a vertical plane, and resonate in high frequencies
What is the function of the annulus/annular ligament?
To help hold the T.M. in place.
What is the function of the ossicular chain?
To sound transmission to oval window and to protect cochlea from intense vibrations by changing axis of rotation of stapes.
Transverse plane
Top or horizontal view. Cut body into upper and lower halves
Proximal
Towarda reference point
Medial
Towards the midline
Superior
Upper or above
(Resonance of middle ear) Effects of increased stiffness is...
Upward shift in resonant frequency
Ossification of the EAM causes...
changes in the angle of the T.M., until about age 5 when it reaches adult position
