Anatomy and Histology of the Ear Flashcards
(31 cards)
What gives blood supply to the external ear?
Posterior auricular and branches from superficial temporal
What innervates the posterior external ear?
Lesser occipital n and greater auricular n
What innervates the middle part of the external ear?
Vagus n and glossopharyngeal n
What innervates over the mastoid process?
Facial n
What supplies the superior, anterior, inferior, and posterior parts of the tympanic membrane?
Facial n, auriculotemporal (from CN V), vagus n, great auricular n
What are the walls of the middle ear?
Roof - tegmental wall Floor - jugular wall Lateral - membranous wall Medial - labyrinthine wall Posterior - mastoid wall
What is the makeup of the external acoustic meatus? What is the makeup of the pharyngotympanic tube?
EAM: distal 2/3 cartilage, proximal 1/3 bony
PT: distal 2/3 bony, proximal 1/3 cartilage
What type of epithelium is the pharyngotympanic tube vs external acoustic meatus?
Pseudostratified columnar vs stratified squamous (with ceruminous glands and hair follicles)
What innervates the tensor tympani m and stapedius m?
Trigeminal n and facial n
What is the stria vascularis?
Lateral wall of scala media, source of endolymph
What is the scala vestibuli continuous with?
The scala tympani
What does the stapes move at the oval window?
The perilymph in the scala vestibuli
What is connected to the round window?
The scala tympani
Where is the organ of corti located?
On the floor of the scala media resting on the basilar membrane
When hair cells in the organ of corti are activated what happens?
They send a signal to the spiral ganglion
What is the path of sound waves in the inner ear?
Stapes moves oval window (connected to scala vestibuli). Perilymph in scala vestibuli vibrates which acts on vestibular membrane which vibrates endolymph in scala media. Endolymph vibrates basilar membrane which distorts sterocilia of hair cells. Pressure in perilymph is transferred to scala tympani and exits via round window
What do the semicircular canals do?
Sense rotational velocity. The anterior canal is in the saggital plane, posterior is in coronal plane, the transverse canal is in the horizontal plane
How do the semicircular canals work?
They have an ampulla at the base that contains a cupula with hair cells inside of it. When the cupula is moved due to head rotation/acceleration the endolymph pushes the cupula (in the opposite direction) which distorts the hair cells
How do the utricle and saccule work?
They are within the vestibule and both contain a macula - hair cells with stereocilia with overlying gelatinous material called otolithic membrane. Otolithic membrane covered with rocks that sense gravity and linear acceleration
What does the utricle detect?
Linear acceleration
What does the saccule detect?
Gravity/which way is up
What happens when stereocilia bend toward kinocilium?
K+ channels open causing depolarization
What happens when stereocilia bend away from kinocilium?
K+ channels close causing hyperpolarization
What drugs target/damage hair cells?
Aminoglycosides and loop diuretics
