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Histology > Ear > Flashcards

Ear Flashcards

1
Q

What are the two major systems of the ear?

A

auditory system: sound perception
vestibular system: balance

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2
Q

What are the three divisions of the ear?

A

external ear
middle ear
internal ear

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3
Q

What is the external ear made up of? What is the shape determined by?

A

auricle (pinna):
- oval appendage projecting from the head surface
- shape is determined by an internal supporting structure of elastic cartilage

hair follicles, sweat glands (ceruminous glands), sebaceous glands cover the auricle

external acoustic meatus:
- air filled tubular space following an s-shaped course to the tympanic membrane (eardrum)

elastic cartilage + skin

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4
Q

State the composition of the external aucustic meatus.

A

wall of the lateral 1/3:
- cartilaginous
- continuous with the elastic cartilage of the auricle

medial 2/3:
- contained within the temporal bone

lined by skin
- continuous with auricle (pinna) skin

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5
Q

How is ear wax formed? What is its real name? What is its function?

A

ear wax - cerumen

  • formation: secretion of ceruminous glands mixes with secretions of sebaceous glands and desquamated cells
  • function: lubricates skin, coats meatal hairs to empede the entry of foreign particles, provides antimicrobial protection from bacteria, fungi and insects)
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6
Q

What is the composition of the middle ear? Location? Lining?

A

location: tympanic cavity (air-filled space in temporal bone)
lined by: simple squamous/cuboidal epithelium
contents: auditory ossicles (3 small bones + 2 movable joints), eustachian tube (auditory tube opening into the nasopharynx + muscles attaching to the ossicles).

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7
Q

What seperates the external ear from the middle ear?

A

tympanic membrane

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8
Q

Why is the middle ear easy to damage?

A

simple epithelial layer (1 cell thick)

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9
Q

What is the function of the auditory tube?

A

equillibrate the pressure in the ear and nose

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10
Q

What is the shape, function and layers of the tympanic membrane?

A

shape: irregular cone

function: barrier b/w external aucustic meatus and middle ear

layers (outside to inside):
- skin of external aucustic meatus (external ear side)
- DENSE connective tissue core with collagen fibers (radially and circularily arranged)
- mucosa (squamous/cuboidal epithelium- middle ear side)

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11
Q

What is the function fo the ear ossicles?

A

amplify sound

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12
Q

How many ossicles does the ear have? What are they?

A

3 ossicles:
1) malleus=hammer (tympanic membrane + incus)
2) incus=anvil (malleus + stapes)
3) stapes=stirrup (fits into the oval window)

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13
Q

What is the function of the ossicles?

A

Convert sound waves to mechanical (hydraulic) vibrations in tissues and fluid filled chambers.

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14
Q

What is the function of the auditory (Eustachian) tube? What is it composed of?

A
  • narrow, flattened chamber
  • lined with ciliated pseudostratified columnar epithelium + goblet cells
  • vents the middle ear equalizing its pressure with the atmospheric pressure.
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15
Q

What is the function of the internal ear?

A

makes the senses work

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16
Q

What does the internal ear consist of?

A

2 labyrinthine compartments (one contained within the other)

1) BONY LABYRINTH:
- system of interconnected cavities and canals in the* temporal bone*

2) MEMBRANOUS LABYRINTH:
- inside bony labyrinth
- complex system of small sacs and tubules forming a continuous space

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17
Q

What is the bony labyrinth composed of?

A

3 connected spaces:
- semicircular canals
- vestibule
- cochlea

18
Q

What is the membranous labyrinth composed of?

A

series of communicating sacs (utricle, saccule and endolymphatic sac) and ducts containing endolymph (3 semicircular ducts, cochlear duct, utriculosaccular duct, and ductus reuniens).

19
Q

What is the major difference bewteen the inner ear and the other 2 ear parts?

A

inner ear is filled with fluid, while the other parts are filled with air.

20
Q

State the location of cells in the inner ear.

A

specialized sensory cells and accessory supporting cells are located in 6 regions in the membranous labyrinth.

  • 3 cristae ampullaris –> ampullae of semicircular ducts
  • 2 maculae –> utricle and saccule
  • spiral organ of Corti
21
Q

What is the function of cristae ampullaris?

A

receptors for angular acceleration of the head

22
Q

What is the function of maculae?

A

receptors for position of the head and its linear movements

23
Q

What is the function of spiral organ of Corti?

A

receptors for sound

24
Q

What is the function of hair cells?

A

mechanoelectric transducers (convert mechanical energy into electrical energy)

25
Q

Why are hair cells called hair cells?

A
  • organized bundle of rigid projections at their apical surface,
  • surface holds a hair bundle formed by rows of stereocilia called sensory hairs
  • rows increase in height in one direction across the bundle
26
Q

What is the kinocilium?

A

in the vestibular system, each hair cell possesses a single true cilium located behind the row of the longest stereocilia

27
Q

What are both hair cell types associated with?

A

afferent and efferent nerves

28
Q

How do type I hair cells look?

A
  • flask-shaped
  • rounded base
  • thin neck
  • surrounded by afferent nerve chalice and a few efferent nerves
29
Q

How do type II hair cells look?

A
  • cylindrical
  • afferent and efferent bouton nerve endings at the base of the cell
30
Q

What does the utricle and saccule maculae contain? What is their function?

A

hair cells - epithelial mechanoreceptors

31
Q

State the composition of hair cells.

A
  • contain hair bundles (on apical surfaces) formed by stereocilia with a single kinocilium
  • overlaid with a gelatin-like otolithic membrane which contains otoliths

otolith= otoconia calcium carbonate

32
Q

State the function of hair cells

A
  • movement of otoliths is detected by hair bundles,
  • hair buncles activate mechanically gated ion channels
  • action potential is generated
  • functions as a sensor for cravity and linear acceleration
33
Q

Which part of the ear does ‘acceleration power’ affect most? How is it affected?

A

gelatin mass= otolithic membrane with otoliths
- affected in the opposite direction

34
Q

Explain the function of the sensory receptors in cristae ampullaris.

A
  • sensory receptors are covered by a gelatin mass= CUPULA
  • no otoliths

cupula is deflected during the flow of endolymoh
- movement within the cupula stimulated the generation of an action potential through the stimulation of mechanically gated ion channels

35
Q

What is the difference between the function of cristae ampullaris and otoliths of hair cells?

A

cristae ampullaris- sensors of angular movements of the head (centrifugal power)

otoliths of hair cells- sensors for gravity and linear acceleration (acceleration power)

36
Q

What is the cochlear canal (labyrinth) divided into?

A

1) scala media / cochlear duct (middle compartment filled with endolymph + spiral organ of Corti)
2) scala vestibuli
3) scala tympani (+ perilymph)

37
Q

What is the cochlear canal in charge of?

A

sound recieving

38
Q

State the composition of the scala media.

A
  • triangular space
  • basilar membrane (bottom) + spiral organ of Corti
  • vestibular membrane (top) (seperates scala media from vestibuli)
  • lateral wall= stria vascularis= produces endolymph
39
Q

What is the spitral organ of Corti composed of?

A
  • hair cells (inner and outer rows),
  • supportive phalangeal cells,
  • pillar cells
40
Q

How is the tectorial membrane formed?

A
  • radially oriented bundles of collagen fibers
  • lateral free edge projects over and attached to the organ of Corti by stereocilia of hair cells.
41
Q

Explain how sound is transmitted.

A
  • stereocilia on hair cells move during interaction with the overlying tectorial membrane
  • tectorial membrane generated an electrical impulse
  • electrical impulse is transmitted to the cochlear nerve
  • sound waves are transmitted from the vibrating tympanic membrane to the oval window by ossicles
  • sound waves produce movement of the perilymph in the scala vestibule
  • movement deflect sthe basilar membrane and spiral organ of Corti to generate electrical nerve impulases (percieved by the brain as sounds)

Histology (20 decks)

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