Histo - Ear Flashcards
What are the 3 components to the Ear?
-
External ear
- takes in sound
-
Middle ear
- ossicles (bones)
- transmit sound from air –> fluid
- ossicles (bones)
-
Internal ear
- fluid moving causes nerves to fire
- hearing
- equilibrium
- fluid moving causes nerves to fire
Name the parts of the ear
What are the components of the External Acoustic Meatus?
- Tympanic membrane (eardrum)
- Hair follicles
-
2 Types of Glands (in submucosa)
- Sebacous glands (SG)
- Ceruminous glands (CB)
- modified apocrine sweat glands
- both secrete ear wax
- modified apocrine sweat glands
What are the components of the Internal Ear?
- Bony Labrynth
- Membrenous Labyrnth
- Ampullae
- Round Window
- Oval Window
- Apex of Cochlea
Tympanic Membrane
- Fibroelastic CT
- Outer part = SSK
- Inner part = Simple cuboidal
- sound in air –> vibrations of tympanic membrane to transmit to middle ear
Middle Ear
Tympanic Cavity
-
Air filled space
- btw eardrum & bone of internal ear
-
Auditory tube (Eustachian tube)
- communicates w/ pharynx anteriorly
- balances air pressure in middle ear
- Interacts w. mastoid cavities (air spaces in temporal bone) posteriorly
- In medial part = 2 regions w/ no bones
- oval window
- round window
Bones (Ossicles)
- 3 bones
- Malleus
- Incus
- Stapes
Muscles - protect oval window/inner ear from loud sounds
- Tensor tympani
- Stapedius
What is a middle ear infection?
Otitis Media (ear infection)
- Caused by infection that come through the Auditory Tubes from respiratory tract
- more common in children
- small & short tubes
- more common in children
Inner Ear
Bony Labyrinth
- contains perilymph
Vestibule
- saccule & utricle within
Semicircular canals
- has semicircular ducts within
Cochlea
- has cochlear duct within
- spiral/cochlear ganglion & process of CN VIII w/in modiolus
Membranous Labyrinth (sensory region w/ hair cells)
- contains endolymph
- surrounded by bony labyrinth
2 connected sacs
- Utricle
- Saccule
3 semicircular ducts
- continuous w/ utricle
- cristae ampullares in each duct
Cochlear duct (organ of hearing)
- continuous w/ saccule
- contains SPIRAL ORGAN of CORTI
Inner Ear Fluids
Perilymph (Bony Labyrinth)
-
similar to CSF & ECF
- little protein
- protects membranous labyrinth
Endolymph (Membranous Labyrinth)
- high in K+
- low in Na+
- similar to ICF
- produced by STRIA VASCULARIS
- vascular epithelium
How does the Vestibular Organ sense equilibrium?
3 semicircular canals
- superior
- horizontal
- posterior
2 sacs (otolith organs)
- saccule
- utricle
- both are CT lined by simple squamous epithelium
- bound to periosteum of bony labryinth
Ampullae are present at the connection of the canals w/ utricle.
-
Maculae = present w/in walls of sacs
- thickeningns w/ many hair cells
- columnar neuroepithelial cells
- supporting cells & synaptic connections
- innv. by vestibular n. (VIII)
Function:
- Detect gravity & moving endolymph
- perpendicular to each other
-
Hair cells have a layer over them = otolithic layer
- gelatinous
- proteoglycans
- otoliths embedded
- CaCO3 & protein
- mending of kinocilia
- Hair cells have stereocilia & single kinocilum
- Basal part of hair cells have synaptic connections w/ nerve fibers
Hair Cells in Vestibular Maculae
-
Mechanoelectrical transducers
- monitor static position
- monitor linear acceleration
- helps maintain equilibrium
-
Single Kinocilium
- rigid
-
Multiple stereocilia
- rigid
- rows that DECREASE in length
-
2 Types of hair cells
- Type I:
- rounded clels
- nerve calyx around them
- Type II
- columnar cells
- typicall synapses
- **BOTH have efferent fibers that connect w/ them on their afferents
- Type I:
Mechanotransduction in Hair Cells in Maculae
- Bending of stereocilia of macular hair cells causes:
- changes to ion channels in the TIPS of stereocilia
- TOWARD kinocilium = DEPOLARIZATION
- open channels
- AWAY kinocilium = HYPERPOLARIZATION
- channels close
What is this?
Maculae
Semicircular Ducts
-
3 semicircular ducts
- come from & return to the utricle
- different orientations to each other
- each has an AMPULLA (enlarged space)
-
crista ampullaris = structures within the ampulla wall
- has hair cells & support cells
- similar to those in maculae
- perpendicular to long axis of duct
- protrudes –> duct
- has cupola (NOT OTOLITHIC LAYER)
- proteoglycan layer
- NO otoliths
- thicker than otolithic layer
- has hair cells & support cells
-
crista ampullaris = structures within the ampulla wall
Hair Cells in Cristae Ampullares
-
Mechanoelectrical transducters
- signal by depolarization & hyperpolarization
-
Detect rotation of head
- endolymph moves w/in duct & deflects hair cells
-
CNS detects input from all 3 sets of cristae hair cells
- interprets the input as head rotation
What is this?
Cristae Ampullaris
What is this?
Vestibular System
Cochlea
Contains 3 parallel regions (scalae)
- 2 3/4 turns w/in cochlea
Scala media/cochlear duct - middle of scalae
- contains ENDOLYMPH
- contains organ of Corti
- organ of hearing
- hair cells –> transduce sound waves into hearing
- contain stria vascularis
- secrete ENDOLYMPH
- vascularized epithelium
- bound by basilar & vestibular membrane
scala vesibule & tympani
- contain PERILYMPH
- one tube –> coiled
- continuous at the apex = helicotreme
What is this?
What is this?
Organ of Corti
- Sits on BASILAR MEMBRANE
- 2 sets of hair cells
- support cells = PHALANGEAL CELLS
- pillar cells = INNER TUNNEL
- 2 sets of hair cells
- Phalangeal cells
- both inner & outer
- support both types of hair cells & nerve endings
- both inner & outer
- Pillar cells
- keratin bundles
- defines inner tunnel
What is this?
Hair Cells in the Organ of Corti
Outer Hair Cells
- 3-5 row
- V-shaped set of steriocilia
Inner Hair Cells
- single row
- linear/shorter/stereocilia
- MAIN HEARING RECEPTORS
- MORE nerve endings!!
Apical part of cells = embedded in tectorial membrane
- tectorial membrane = acellular
- made of collagen & proteoglycans
BOTH:
- innv by AFF bipolar neurons in SPIRAL GANGLION
- have EFF nerve endings
- hair cells = mechanoelectrical transducers
Process of Hearing
- Sound waves vibrate the tympanic membrane
- moves ossicles & oval window
- Energy transfers to PERILYMPH
- pressure waves move along SCALA VESTIBULE
- causes displacement of vestibular or basilar membranes –> thus ENDOLYMPH
- Activates nerve endings on the hair cells
- Communicates along CN VIII —> CNS
- perceived sound it can interpret
What is this?
Hair Cells in the Organ of Corti ‐ SEM
What is this?
Spiral Ganglion
- AKA: Cochlear ganglion
- forms part of CN VIII
- Within bony modiolus (center of cochlea)
-
BIPOLAR neurons
- peripheral part = innv receptor cells (hair cells)
- central part = enters modiolus
