Unit VIII - Ear Pt. 1 Flashcards
What is the embryologic structure of ectodermal thickening on the lateral “head” that gives rise to the ears?
Placode
What is the pathway of the embryological formation of the ear?
Placode –> auditory pit –> auditory vesicle –> most of membranous inner ear
What structures of the ear are derived from the first pharyngeal pouch?
Auditory tube and tympanic cavity
From where is the malleus derived?
Dorsal end of the ventral mandibular cartilage
From where does the incus arise?
Dorsal end of the first pharyngeal arch
What ear structure is derived from the dorsal end of the second pharyngeal arch?
Stapes
From where does the tympanic membrane develop?
Interstitial mesoderm
From where does the external acoustic canal develop?
First pharyngeal groove
From where does the auricle develop?
A groove next to the first pharyngeal groove
What are the three portions of the ear?
External, middle, and inner
What is another name for the auricle?
Pinna
What tissue makes up the auricle?
Cartilage
What is the function of the auricle?
Funnel sound waves into the external acoustic meatus
What are the three extrinsic ear muscles that position the auricle?
Anterior, superior, and posterior auricular muscles
Which auricular muscle inserts on the front of the helix?
Anterior auricular muscle
Which auricular muscle is the largest?
Superior auricular muscle
Where does the superior auricular muscle insert?
On superior side of auricle
What is the smallest auricular muscle?
Anterior auricular muscle
Where does the posterior auricular muscle insert?
Lower, posterior aspect of concha
What are the intrinsic ear muscles?
Helicis major and minor, tragicus, antitragicus, transverse muscles of the auricle, oblique muscles of the auricle
About how long is the external acoustic meatus?
1 inch
What shape is the external acoustic meatus?
S-shaped
What part of the external acoustic meatus is within a bone? Which bone?
Medial 2/3; temporal bone
What covers the entire length of the external acoustic meatus?
Skin with modified sweat glands
What do the modified sweat glands of the external acoustic meatus produce?
Cerumen
Where does the external acoustic meatus terminate?
Tympanic membrane
What motion makes otoscopic examination possible even though the length of the external acoustic meatus is not straight?
Gently pulling out, down, and forward on the lobule
What makes up the blood supply to the external ear?
Posterior auricular branch of external carotid artery
Anterior auricular branch of superficial temporal artery
Auricular branch from the occipital artery
What makes up the sensory supply to the external ear?
Auriculotemporal nerve of the mandibular division of trigeminal
Auricular branch of vagus
Great auricular nerve (C2 and C3)
What makes up the motor supply to the external ear?
Temporal and posterior auricular branches of the facial nerve
Where does sympathetic supply to the external ear come from?
Superior cervical ganglion
The middle ear is between what structures?
Tympanic membrane and inner ear
What are the two parts of the middle ear?
Tympanic cavity and epitympanic recess
What are the three small bones found in the middle ear?
Stapes, malleus, and incus
What two muscles are located in the tympanic cavity?
Stapedius and tensor tympani
What is the smallest muscle in the body?
Stapedius
What forms the roof/tegmental wall of the middle ear?
Petrous part of the temporal bone
What forms the floor/jugular wall of the middle ear?
Thin layer of bone separating the cavity from the internal jugular vein
The small opening in the floor/jugular wall of the middle ear serves what purpose?
Entrance for the tympanic branch of the glossopharyngeal nerve
What forms the lateral/membranous wall of the middle ear?
Almost entirely by tympanic membrane (slight bony part adjacent to epitympanic recess)
What wall of the middle ear is incomplete?
Posterior/mastoid wall
What is the opening between the tympanic cavity and the mastoid air cells?
Aditus of the mastoid antrum (in the posterior/mastoid wall)
What is the opening that the tendon of the stapedius muscle passes through and where is it located?
Pyramidal eminence; posterior/mastoid wall of middle ear
Where do we find the opening for the chorda tympani?
Posterior/mastoid wall of middle ear
The carotid wall of the middle ear separates the cavity from what vessel?
Internal carotid artery
What are the openings found in the carotid wall of the middle ear?
Large opening for pharyngotympanic tube
Opening for tensor tympani
Small exit for chorda tympani
Where does the chorda tympani enter and exit in the middle ear?
Enter - posterior/mastoid wall
Exit - carotid wall
What is the boundary between the middle ear and the inner ear?
Labyrinthine/medial wall
What is the impression made by the cochlea in the labyrinthine?
Promontory
What covers the promontory of the labyrinthine, and what makes it up?
Tympanic plexus; tympanic branch of C.N. IX, branches from the internal carotid plexus
What does the tympanic plexus that covers the promontory supply?
Mucous membranes of middle ear, mastoid area, and pharyngotympanic tube
Which nerve leaves the tympanic plexus and travels to the otic ganglion?
Lesser petrosal nerve
What bone attaches to the oval window on the medial wall of the inner ear?
Stapes
Where are the oval and round windows located?
Labyrinthine/medial wall
The prominence of the facial canal is an impression of bone that is formed by a canal conducting what nerve?
Facial nerve
In what wall does the lateral semicircular canal form a small impression?
Medial wall (labyrinthine)
Where are the ossicles located specifically?
Tympanic cavity
What is the largest auditory ossicle?
Malleus
What does the malleus contact?
Tympanic membrane
What is the function of the incus?
Transmit vibrations from malleus to stapes
Where does the base of the stapes sit?
Against oval window
What makes up the blood supply to the middle ear?
Anterior tympanic branch of internal maxillary artery
Tympanic branch of internal carotid artery
What is the sensory nerve supply to the middle ear?
Tympanic nerve of C.N. IX
What is the motor supply to the middle ear?
Nerve to the stapedius of the facial nerve
Medial pterygoid nerve of the mandibular division of the trigeminal
What muscle does the medial pterygoid nerve of the mandibular division of the trigeminal nerve supply?
Tensor tympani
What makes up the sympathetic supply of the middle ear?
Caroticotympanic nerves carry vasomotor and secretomotor fibers from superior cervical ganglion by way of internal carotid plexus
