Lecture 22-Ear

Question 1

Describe the histology of the auricle:

Answer 1

This is the pinna of the ear and auditory canal. INTEGUMENT OVERLYING ELASTIC CARTILAGE.

Question 2

Describe the histology of the external Auditory meatus:

Answer 2

Outer third of ear is elastic. Inner 2/3 is bone.

Lining of ear canal is stratified squamous epithelium w/ sebaceous glands and ceruminous glands

Question 3

Describe the histology of the tympanic membrane.

Answer 3

Vascularized innervated CT

External surface-covered by thin skin
Internal- simple cuboidal epithelium

Question 4

Identify the three auditory ossicles and describe their relationship to each other.

Answer 4

Malleus: attaches to tympanic membrane

Incus: middle bone. “Anvil”

Stapes: shaped like stirrup for opening for the stapedial artery. Inserts on oval window.

Question 5

Name the 2 openings from the middle ear and relate to the structure of the inner ear.

Answer 5

Oval window: stapes attaches and covers. Opens to Scalia vestibuli.

Round window: membrane-covered region is at the end of the Scalia tympani

Question 6

List the 2 muscles of the middle ear and relate to the structure of the inner ear.

Answer 6

Tensor tympani: inserts on the malleus

Stapedius: inserts on the stapes

These muscles contract reflexively to loud sounds to dampen the vibrations

Question 7

Describe each of the 4 regions of the inner ear

Answer 7

Bony labyrinth: canals [high Na+ perilymph]. Semicircular canals, cochlea, Scala vestibuli, scala tympani.

Membranous labyrinth:embedded w/in chambers of bony labyrinth w/ high [K+] endolymph.

Vestibular organ: sensory organs that respond to changes in position.

Auditory organ: cochlea

Question 8

Fig 9-26: membranous labyrinth

Answer 8

Semicircular ducts open into utricle.
Ampullae are dilation connecting the ends of the semicircular ducts to the urticle.
Cristae ampullares in the ampulla of each semicicular duct.

Question 9

Describe the structure of the maculae in relation to epithelium, hair cells, and otolithic membrane

Answer 9

Columnar supporting cells and vestibular hair cells: stereocilia.
Hair cells contact afferent nerve endings.
Otolithic membrane is gelatinous layer containing Ca+CO3 crystals -otoliths.
Steroecilia embedded in gelatinous layer. Movement displaces this.

Question 10

Describe the structure of the cristae ampullare in relation to epithelium, hair cells, and otolithic membrane

Answer 10

Columnar supporting cells and hair cells: similar to maculae.
Cupula: gelatinous layer w/o otolithic membrane. Creates shear forces btw the semicircular canals and contained fluid. Movement of fluid displaces the cupula and causes stereocilia to bend.

Question 11

Describe the structure of the auditory organ (cochlea), including its compartments, membranes, and related components, including the stria vascularis and organ of corti

Answer 11

Scala media: (cochlear duct) organ of corti-basilar membrane. Endolymph. Stria vascularis: lateral wall-makes endolymph. High [K+]

Scala vestibula: Perilymph.

Scala tympani: perilymph.