Ear Flashcards
Ear components:
- contains Vestibulocochlear organ
- functions in balance and hearing
- consists of external, middle and inner parts
Purpose of the ear:
Provides a mechanism for detection of sound waves and conversion to information that can be perceived by the CNS, also contains mechanism for balance and equilibrium
External ear is composed of:
Oval auricle (pinna) and the external acoustic meatus (EAM, auditory canal)
The auricle ______ and the EAM _____ to the tympanic membrane.
Collects the sound waves; conducts the sound waves to tympanic membrane
Tympanic membrane separates:
External and middle ear compartments
The auricle is:
A single elastic cartilage covered on both sides by hairy skin, the cartilage is prolonged medially where it is continuous with the cartilage of the EAM. The ear lobe contains no cartilage but has small blood vessels making it ideal for small blood samples
Sensory innervation for the auricle arises from:
C2, C3 - great auricular n. and lesser occipital n. and
V3 - auriculotemporal n.
Movement of the tympanic membrane (TM):
The TM is concave with a central depression (umbo) formed by the malleus - the cone of light can be seen radiated anteroinferiorly from the umbo.
TM moves in response to air vibrations that transverse the EAM –> TM moves against malleus –> vibrations transmitted via remaining auditory ossicles from middle –> inner ear
Sensory innervation for the external acoustic meatus comes from:
V3, VII, X.
The EAM extends from the auricle to the tympanic membrane, the outermost 1/3 of the EAM is cartilaginous and contains ceruminous glands for the production of ear wax - cerumen. The remaining inner part is bony. Where the EAM becomes bony, the diameter narrows - ISTHMUS - where foreign bodies - where foreign bodies become lodged in children
Innervation to the external part of the TM:
V3, VII, X - essentially the same as the EAM
Innervation to the internal part of the TM is by:
IX - Glossopharyngeal
Perforation of the TM occurs by:
Foreign bodies, infection, excessive pressure, or skull fracture - severe bleeding or cerebral spinal fluid drainage thru the TM and EAM is indicative of a skull fracture and illustrates the close proximity of the external and middle ear divisions to the meninges of the brain
Middle ear connected to nasopharynx by:
Auditory (eustachian) tube
Middle ear comprises:
A narrow cavity in the petrous portion of the temporal bone, connected anteriorly to the NASOPHARYNX by the AUDITORY (Eustachian) tube and posterosuperiorly to mastoid cells via the
Middle ear connected posterosuperiorly to mastoid cells via:
The mastoid antrum
The middle ear contains:
Auditory ossicles, stapedius and tensor tympani muscles, chorda tympani n, and tympanic plexus of nerves
Auditory ossicles located in:
Epitympanic recess
Tympanic cavity (shaped like a box):
- Roof forms the TEGMEN TYMPANI and separates the tympanic cavity from the dura on the floor of the middle cranial fossa
- Floor separates tympanic cavity from the internal jugular v.
- Lateral wall is formed by the tympanic membrane
- Medial wall separates the tympanic cavity from the inner ear
Contents of the tympanic cavity - MEDIAL WALL:
PWSF - the MEDIAL Piccolo Was So Fascinating
- Promontory - formed by the basal portion of the cochlea
- Windows - vestibular (oval) and cochlear (round) windows
- Stapes and stapedius m.
- Facial n.
Contents of tympanic cavity - LATERAL WALL
MICTT - My Itchy Cochlea Tickles Today
- Malleus
- Incus
- Chorda tympani nerve
- Tensor tympani muscle
- Tympanic membrane
On the medial wall, the _________ of CN _____ passes thru a hole in the floor of the tympanic cavity and spreads out across the round promontory as the TYMPANIC PLEXUS to provide ___ innervation to the middle ear.
Tympanic nerve; IX.
This plexus supplies sensory innervation to the middle ear.
What supplies sensory to the middle ear?
Tympanic plexus (comes from tympanic nerve of IX)