Auditory Apparatus Flashcards
(84 cards)
1
Q
What is the External Ear composed of?
A
Composed of the shell-like auricle (pinna) that collects sound and the external acoustic meatus which conducts sound to the tympanic membrane.
2
Q
What is the auricle composed of?
A
Composed of an irregularly shaped plate of elastic cartilage covered by thin skin.
3
Q
Concha of auricle:
A
o Deepest depression
4
Q
Helix:
A
o Elevated margin of the auricle
5
Q
Lobule:
A
o Consists of fibrous tissue, fat and blood vessels
6
Q
Tragus:
A
o Tongue like projection overlapping the opening of the external acoustic meatus
7
Q
Arterial supply of the auricle:
A
o Posterior auricular and superficial temporal aa.
8
Q
Innervation of the auricle: (3)
A
o Great auricular nerve supplies
- Back of the ear
- Posterior aspect of the front of the ear
o Auriculotemporal nerve (from mandibular n. (CN V3))
- Anterior aspect of the front of the ear
o Auricular br. of vagus nerve (with contribution from facial n.)
- Skin of the concha
9
Q
External acoustic meatus: (2)
A
- Ear canal leading inward through the tympanic part of the temporal bone from the auricle to the tympanic membrane
- 2-3 cm in adults
10
Q
External acoustic meatus:
* Lateral third: (3)
A
o Slightly S-shaped and cartilaginous
o Lined with skin that is continuous with the auricular skin
o Ceruminous and sebaceous glands in the subcutaneous tissue produce cerumen (ear wax)
11
Q
External acoustic meatus:
* Medial 2 thirds:
A
o Bony and lined with thin skin that is continuous with the external layer of the tympanic membrane
12
Q
External acoustic meatus:
* Innervated by…
A
- Innervated by auriculotemporal n. (superior & anterior walls) and vagus n. (posterior & inferior walls)
13
Q
What is the Tympanic Membrane? (4)
A
- Approximately 1cm in diameter
- Thin, oval, semitransparent membrane at the medial end of the external acoustic meatus
- Forms a partition between the external acoustic meatus and the tympanic cavity of the middle ear
- Covered with skin externally and mucosa of the middle ear internally
14
Q
Tympanic Membrane
* Umbo-
A
- Umbo- peak of central depression
15
Q
Tympanic Membrane
* Pars flaccida-
A
- Pars flaccida- thin membrane superior to lateral process of malleus
16
Q
Tympanic Membrane
* Pars tensa-
A
- Pars tensa- remainder of the membrane
17
Q
Tympanic Membrane
* Innervation: (3)
A
o Auriculotemporal n. (external supero-anterior 2 thirds)
o Auricular branch of vagus n. (external postero-inferior
o Glossopharyngeal n. (internal surface)
18
Q
What is the middle ear (Tympanic Cavity)?
A
- Narrow air-filled chamber in the petrous part of the temporal bone
19
Q
Middle Ear
Tympanic Cavity:
* Has 2 parts:
A
o Tympanic cavity proper- space directly internal to the tympanic membrane
o Epitympanic recess- space superior to the tympanic membrane
20
Q
Middle Ear
Tympanic Cavity:
* Communications: (2)
A
o Anteromedially- nasopharynx by the pharyngotympanic tube (Eustachian tube)
o Posterosuperiorly- mastoid cells through the mastoid antrum
21
Q
What is the middle ear lined with?
A
- Lined with mucosa that is continuous with the pharyngotympanic tube, mastoid cells and mastoid antrum
22
Q
- Walls of the tympanic cavity:
1. Tegmental wall (roof):
A
o Thin plate of bone (tegmen tympani) separating tympanic cavity from middle cranial fossa
23
Q
- Walls of the tympanic cavity:
2. Jugular wall (floor)
A
o Bone separating tympanic cavity from superior bulb of jugular vein
24
Q
- Walls of the tympanic cavity:
3. Membranous wall (lateral)
A
o Convex tympanic membrane with bony wall of epitympanic recess superiorly
25
* Walls of the tympanic cavity:
4. Labyrinthine wall (medial): (2)
o Promontory of labyrinthine wall formed by initial part of cochlea
o Has oval and round windows
26
* Walls of the tympanic cavity:
5. Mastoid wall (posterior): (2)
o Has aditus to mastoid antrum connecting it to the mastoid cells
o Canal for facial nerve descends between the posterior wall and the antrum medial to the aditus
27
* Walls of the tympanic cavity:
6. Carotid wall (anterior): (2)
o Separates tympanic cavity from carotid canal
o Superiorly- opening for pharyngotympanic tube and canal for the tensor tympani
28
What is the Mastoid antrum? (4)
o Cavity in the mastoid process of the temporal bone
o Separated from the middle cranial fossa by tegmen tympani
o Common cavity into which the mastoid air cells open
o Lined by mucosa
29
Contents of the middle ear: (4)
o Auditory ossicles
o Stapedius and tensor tympani muscles
o Chorda tympani (branch of facial nerve)
o Tympanic nerve plexus
30
What is the Pharyngotympanic Tube? (4)
* Connects the tympanic cavity to the
nasopharynx
* Opens posterior to the inferior nasal meatus
* Posterolateral third is bony and the rest is
cartilaginous
* Lined by mucosa that is continuous posteriorly
with the tympanic cavity and anteriorly with the
nasopharynx
31
What is the function of the Pharyngotympanic Tube?
o Equalizes pressure in the middle ear with the atmospheric pressure to allow for free movement of the tympanic membrane
32
Pharyngotympanic Tube:
* The walls of the _________ part are normally in apposition (the tube is closed)
* The tube is opened by _______ veli palatini and ______ veli palatini
cartilaginous
levator
tensor
33
Pharyngotympanic Tube:
* Blood supply: (3)
o Ascending pharyngeal artery from the external carotid artery
o Middle meningeal artery from maxillary artery
o Artery of pterygoid canal from maxillary artery
34
How is the Pharyngotympanic Tube drained?
* Drained by pterygoid venous plexus
35
Pharyngotympanic Tube:
* Innervation: (2)
o Nerves from the tympanic plexus (glossopharyngeal nerve fibers)
o Nerves from pterygopalatine ganglion
36
What are Auditory Ossicles?
* Form a mobile chain of small bones across the tympanic cavity from the tympanic membrane to the oval window
37
Oval window-
o Oval window- opening on the labyrinthine wall of the tympanic cavity leading to the vestibule of
the bony labyrinth
38
Auditory Ossicles:
* First bones to ______
* Covered with mucosa but lack ________
ossify
periosteum
39
What is the 1. Malleus? (3)
o Attaches to the tympanic membrane
o Moves with the membrane
o Functions as a lever
40
1. Malleus
o Head: (3)
- Round and superior
- Lies in the epitympanic recess
- Articulates with incus
41
1. Malleus
o Neck: (2)
- Lies against the flaccid part of the tympanic membrane
- Chorda tympani crosses the medial surface
42
1. Malleus
o Handle: (3)
- Embedded in the tympanic membrane
- Tendon of tensor tympani inserts into the handle near the neck
- Tip at the umbo
43
What is the 2. Incus? (2)
o Between the malleus and stapes, and articulates with them
o Has a body and 2 limbs
44
2. Incus
o Body: (2)
- Lies in the epitympanic recess
- Articulates with the head of the malleus
45
2. Incus
o Long limb: (2)
- Parallel to the handle of the malleus
- Interior end articulates with stapes with its
medial lenticular process
46
2. Incus
o Short limb:
- Connected by a ligament to the posterior wall of the tympanic cavity
47
What are 3. Stapes? (2)
o Smallest ossicle
o Has a head, 2 limbs and a base
48
3. Stapes
o Head: (2)
- Directed laterally
- Articulates with incus
49
3. Stapes
o Base: (3)
§ Fits into the oval window on the medial wall of the tympanic cavity
§ Attached to the margins of the oval window by an anular ligament
§ Considerably smaller than the tympanic membrane
* Vibratory force is increased 10 times
* Increases the force but decreases the amplitude of vibrations
50
* Associated muscles:
o Tensor tympani: (3)
- Short muscle that pulls the handle of the malleus medially
- Tenses the tympanic membrane and reduces amplitude of its oscillations
- Prevents damage to internal ear when exposed to loud sounds
51
* Associated muscles:
o Tensor tympani
Innervation:
- Innervation- mandibular nerve
52
* Associated muscles:
o Stapedius: (4)
- Tiny muscle inside the pyramidal eminence (hollow prominence on the posterior wall of the
tympanic cavity)
- Inserts onto the neck of the stapes
- Pulls the stapes posteriorly and tilts its base in the oval window
- Reduces excessive movement of the stapes and reduces its oscillatory range
53
* Associated muscles:
o Stapedius
Innervation:
- Innervation- nerve to stapedius from facial nerve
54
What is the Internal Ear? (3)
* Contains the vestibulocochlear organ buried in the petrous part of the temporal bone
* Membranous labyrinth contains endolymph
* Bony labyrinth surrounds membranous labyrinth and contains perilymph
55
What is the Bony Labyrinth? (2)
* Series of cavities (cochlea, vestibule and semicircular canals)
* Contained within the otic capsule of the petrous part of temporal bone
56
1. Cochlea: (2)
o Shell-shaped part of the bony labyrinth that contains the cochlear ducts
o Part of the inner ear concerned with hearing
57
Where does the Spiral canal of the cochlea begin?
- Begins at the vestibule and makes 2.5 turns around a bony core
58
1. Cochlea:
o Modiolus: (3)
- Cone-shaped core of spongy bone around which the spiral canal turns
- Contains canals for blood vessels and the distribution of the cochlear nerve
- Apex is directed laterally, anteriorly and inferiorly
59
1. Cochlea:
o Promontory of the labyrinthine wall:
- Produced by the large basal turn of the cochlea
60
1. Cochlea:
o Cochlear aqueduct:
- Communication between the bony labyrinth and the subarachnoid space superior to the
jugular foramen at the basal turn
61
1. Cochlea:
o Round window:
- Closed by the secondary tympanic membrane
62
What is the vestibule? (3)
o Small oval chamber 5mm long
o Contains the utricle and saccule
o Continuous with the bony cochlea anteriorly and the semicircular canals posteriorly
63
2. Vestibule:
o Vestibular aqueduct: (4)
- Communication between the posterior cranial fossa and the vestibule
- Extends to the posterior surface of the petrous part of the temporal bone
- Opens posterolateral to the internal acoustic meatus
- Transmits the endolymphatic duct and 2 small blood vessels
64
2. Vestibule:
o Oval window:
- Found on the lateral wall, occupied by the base of the stapes
65
What are the 3. Semicircular canals? (4)
o Communicate with the vestibule of the bony labyrinth
o Lie posterosuperior to the vestibule
o Set at right angles to each other
o Each canal forms 2 thirds of a circle and 1.5mm in diameter (except for the bony ampulla)
66
How many openings do the semicircular canals have?
o The canals only have 5 openings
- The anterior and posterior canals have one limb common to both
o Lodged within the canals are the semicircular ducts
67
What is Membranous Labyrinth? (2)
* Consists of a series of communicating sacs and ducts suspended in the bony labyrinth
* Contains endolymph
68
What is endolymph?
o Watery fluid similar in composition to intracellular fluid
69
What are the two divisions of the Membranous Labyrinth? (2)
* Composed of 2 functional divisions- vestibular labyrinth and cochlear labyrinth
* The 2 divisions are connected via the ductus reuniens between the saccule and cochlear duct
70
1. Vestibular labyrinth:
o Semicircular ducts:
- Open into the utricle through 5 openings
71
1. Vestibular labyrinth:
o Utriculosaccular duct: (2)
- Communication between the utricle and saccule
- The endolymphatic duct arises from here
72
1. Vestibular labyrinth:
o Endolymphatic duct: (3)
- Traverses the vestibulocochlear aqueduct
- Emerges through the bone of the posterior cranial fossa
- Expands into a blind pouch- the endolymphatic sac
73
1. Vestibular labyrinth:
o Endolymphatic sac: (3)
- Located between the 2 layers of dura mater on the posterior surface of the petrous part of
the temporal bone
- Storage reservoir for excess endolymph
- Formed by the blood capillaries in the membranous labyrinth
74
1. Vestibular labyrinth:
o Maculae: (5)
- Specialized sensory epithelium in the utricle and saccule
- In the utricle- found on the floor, parallel to the base of the cranium
- In the saccule- vertically placed on the medial wall
- Sensitive to gravity and linear acceleration or deceleration
- Hair cells in the maculae are innervated by fibres of the vestibular division of the vestibulocochlear nerve
75
1. Vestibular labyrinth:
o Ampullae: (4)
- Each semicircular duct has an ampulla at one end
- Ampullary crest- area in the ampullae that have hair cells sensitive to rotational motion
- Hair cells record movements of the endolymph in the ampullae resulting from head rotation
- Hair cells in the ampullary crests are innervated by fibers of the vestibular division of the vestibulocochlear nerve
76
What is the cochlear duct? (2)
o Spiral tube closed at one end and triangular in cross-section
o Firmly suspended across the cochlear canal between the spiral ligament on the external wall of the canal and the osseous spiral lamina of the modiolus
77
Cochlear duct:
o The duct divides the canal into 2 channels: (3)
- Scala vestibuli
- Scala tympani
- The 2 channels are filled with perilymph and join at the apex of the cochlea- the helicotrema
78
* Cochlear duct:
o Roof of duct-
o Floor of duct-
o Roof of duct- vestibular membrane
o Floor of duct- basilar membrane
79
What is the spiral organ of corti in the cochlear? (4)
- Receptor of auditory stimuli on the basilar membrane
- Overlaid by tectorial membrane
- Contains hair cells embedded in the tectorial membrane
- Hair cells innervated by cochlear division of the vestibulocochlear nerve
80
Conduction of sound through the ear: (7)
81
What is the Internal Acoustic Meatus? (2)
* Narrow canal that runs laterally for 1cm within the petrous part of the temporal bone
* It opens in the posteromedial part of the bone
82
Internal Acoustic Meatus:
* Closed laterally by a thin, ________ plate of bone that separates it from the internal ear
* Facial nerve, _________ nerve and blood vessels pass through the plate of bone
perforated
vestibulocochlear
83
* The vestibulocochlear nerve divides near the lateral end of the internal acoustic meatus into: (2)
o Cochlear nerve
o Vestibular nerve
84
Applied Anatomy
Otitis Media: (5)
* Infection of the middle ear
* Inflammation and swelling of the mucosa lining the tympanic cavity may cause blockage of the
pharyngotympanic tube
* Scarring of the ossicles limits their ability to move in response to sound
* Due to continuity of the middle ear and mastoid antrum, mastoiditis can result as a complication
* Facial nerve can be affected the infection spreads beyond the middle ear and will result in facial nerve palsy
