Anatomy of the Ear Flashcards
3 divisions of the ear
External ear: from auricle to TM
Middle ear: from TM to stapes
Inner ear: encased in temporal bone
Contents of middle ear
Auditory ossicles (malleus, incus, stapes)
Stapedius and tensor tympani mm
Chorda tympani n. (Branch of facial)
Tympanic plexus of nn
Contents of inner ear
Vestibulocochlear organ including cochlea, vestibule, and semicircular canals
The ear has protective mechanisms from loud sounds. For example, the ______ muscle pulls the stapes posteriorly and tilts its base in the oval window, thereby tightening the ____ ligament and reducing oscillatory range. This also prevents excess movement of the stapes.
The _____ m. Pulls the malleus handle medially, tensing the TM and reducing the amplitude of its oscillations, which also protects from loud sounds
Stapedius; anular
Tensor tympani
Major structures of external ear
Helix Antihelix Tragus Antitragus Concha
Blood supply to external ear
Superiorly:
Anterior auricular arteries, which branch from superficial temporal a.
Inferiorly:
Posterior auricular a. which branches from the external carotid a. (Also gives off posterior anastomosing arcades)
Shape and length of external auditory meatus and its relation to otoscopic exam
2-3 cm in adults
Lateral third is slightly S shaped and cartilaginous
Medial two-thirds is bony so it cannot be manipulated
On otoscopic exam in adults, helix is pulled posterosuperiorly to reduce curvature of external acoustic meatus
Size of TM
1 cm in diameter
Describe orientation of TM
Concave toward external acoustic meatus with a shallow depression called the umbo
The central axis of the TM passes perpendicular through the umbo, running anterior and inferiorly as it runs laterally — thus it is oriented like a satellite dish positioned to receive signal from the ground in front of and to the side of the head
Superior to the lateral process of the malleus, the TM is thin, called the ____ ______ which lacks radial and circular fibers that are present in the remainder of the membrane — called the ____ _____
Pars flaccida
Pars tensa
The external surface of the TM is supplied by the ______ n. with some innervation by a small auricular branch of the ______ n., which may cause a ______ response when irritated
Auriculotemporal (branch of V3); vagus; cough
The internal surface of the TM is supplied by what n?
Glossopharyngeal n.
What are the 6 walls of the middle ear cavity?
Roof = tegmental wall Floor = jugular wall
Membranous lateral wall
Labyrinthine medial wall
Mastoid wall = posterior wall
Carotid wall = anterior wall
The tegmental wall (roof of middle ear) is formed from thin plate of bone called ____ ____ which separates the tympanic cavity from dura mater on floor of middle cranial fossa
Tegmen tympani
The jugular wall forms the floor of the middle ear, a layer of bone that separates the cavity from the superior bulb of the _______ v.
IJV
The membranous lateral wall of the middle ear cavity is formed by the peaked convexity of the TM. Superiorly it is formed by the lateral bony wall of the _____ ______. The handle of the malleus is attached to the TM, and its head extends into the above space.
Other structures associated with lateral wall are the _____ n. on the floor, which goes up to the tympanic plexus on the promontory and merges with it, continuing up as the _______ n. to the otic ganglion.
Also the _____ n. and the ______ canal, which are above the promontory, foot plate of stapes, and round window
Epitympanic recess
Tympanic n.; lesser superficial petrosal n.
Facial; lateral horizontal semicircular
The medial wall of the middle ear (labyrinthine wall) separates the tympanic cavity from the inner ear. It features the ______, which is formed by the initial part (basal turn) of the cochlea, as well as the oval and round windows
Promontory
The posterior wall (mastoid wall) of the middle ear cavity features an opening in the superior portion called the aditus to the mastoid antrum, connecting the tympanic cavity to the mastoid cells. This serves as a canal for the _____ n. to descend between the posterior wall and antrum, medial to the aditus.
This is also the location of the pyramidal process containing the tendon of the ______ m.
Also in this region is the ______, a branch of the facial nerve that supplies taste sensation to anterior 2/3 of tongue
Facial
Stapedius
Chorda tympani
The anterior (carotid) wall of the middle ear cavity separates it from the carotid canal. Superiorly it has the opening of the _______ and the canal for the _______ m.
Pharyngotympanic tube; tensor tympani
The ____ is the ossicle that attaches to the TM.
Its head lies in the epitympanic recess and articulates with the ______.
The neck lies against the ________
Malleus
Incus
Pars flaccida
The handle of the malleus is embedded in the TM, thus the malleus moves with the membrane. The handle serves as the insertion point for the tendon of what muscle?
Tensor tympani m
The _____ is located between the malleus and stapes, articulating with each. Its large body lies in the _____ ______ where it articulates with the malleus.
The inferior end of one of its limbs articulates with the stapes via the _____ process.
The other limb is connected by a ligament to the posterior wall of the tympanic cavity
Incus; epitympanic recess
Lenticular
The head of the stapes is directed laterally, as it articulates with the _____
The base (footplate) fits into the ____ ____ on the medial wall of the tympanic cavity
Incus
Oval window
Origin and insertion of tensor tympani m
Arises from superior surface of cartilaginous part of eustachian tube, greater wing of sphenoid, and petrous part of temporal bone
Inserts on handle of malleus
Action of tensor tympani m.
Pulls handle of malleus medially, tensing the TM and reducing amplitude of its oscillation
Innervation of tensor tympani m
Mandibular n. (V3)