- pinna (elastic cartilage), external auditory meatus & ceruminous (ear wax) and sebaceous glands

Contents of External Ear

- skin --> collagen --> mucous membrane

- thin keratinized stratified squamous --> collagen (outer radial, inner circular fibers) --> simple cuboidal/squamous

- collagen reduced at pars flaccida (top)

Tympanic Membrane

- irregular space within temporal bone lined by cuboidal epithelium

- connects middle ear with pharynx (balances pressure)

- mastoid air cells posteriorly

- ossicles --> oval/round (superior/inferior) window

Middle Ear

- bony and membranous labyrinths

- CN VIII present in two divisions

- Cochlea (organ of Corti), Saccule and utricle (static position), and 3 Semicircular canals (angular movement)

- lines the bony labyrinth of the inner ear

- bears mesenchymal squamous cells

Endosteum

- lines the membranous labyrinth

Ectodermally derived simple squamous epithelium

- fills the bony labyrinth

- Sodium-rich

Perilymph

- fills the membranous labyrinth

- made by stria vascularis via intraepithelial capillaries

- Potassium-rich

Endolymph

- pear-shaped with a cup-shaped afferent nerve ending at its base

- has efferent endings on the calyx

- have "stereocilia" arranged in increasing length as a single cilium (kinocilium)

Vestibular type I hair cells

- cylindrical with both afferent and efferent nerve endings

- have "stereocilia" arranged in increasing length as a single cilium (kinocilium)

Vestibular type II hair cells

- the "flapper valve" in the crista ampullaris

- gelatinous structure that curies the microvilli and cilia of receptor cells

Cupula

- gelatinous layer with otoliths (otoconia) found in this inner ear structure

- receptor cell surface processes buried in the gelatinous layer

Maculae

- scala vestibuli --> vestibular (Reissner's) membrane --> Cochlear duct --> Organ of Corti --> basilar membrane --> scala tympani

Compartments of Cochlea

- point at the center of cochlea where scala vestibuli and tympani meet

helicotrema

- the cochlea wraps around this core of spongy bone which contains the spiral ganglion

Modiolus

Does the width of the basilar membrane increase or decrease from the oval window to the helicotrema?

Increase (high-->low frequencies)

- range of hearing in a young adult

20 to 15k Hz

- located on the lateral wall of the cochlear duct

- produces endolymph (potassium-rich)

- contains intra-epithelial capillaries

- basal plasma membrane folding w/ mitochondria

Stria vascularis

- bony extension of the modiolus

- located next to spiral limbus

Spiral Lamina

- contains hair cells of the sensory apparatus

- consists of tectorical membrane, hair cells

- supported by spiral limbus/lamina

Organ of Corti

- overlies and contains the stereocilia of the sensory hair cells

Tectorial membrane

- ganglion located in the modiolus

Spiral ganglion

- encircles the inner spiral tunnel

Inner/Outer pillar cells

- do not contain cilium

- the sensory cells of the inner ear

- 1 row inner, 3-5 rows outer

- like vestibular receptor cells (type II hair cells)

Inner/Outer hair cells

- perform supportive role and surround inner hair cells completely

- surround the base of outer hair cells and have a process that runs apically and expands into a plate

- supports apical region of hair cell

- form tight junctions between themselves and with hair cells

- isolates lumen of cochlear duct from the spaces in the organ of Corti

Phalangeal cells

- this occurs to initiate hair cell depolarization

movement of stereocilia