Ear

Question 1

contrast perilymph vs endolymph

Answer 1

• perilymph:
  
  • fluid in the bony labryinth
  • resembles extracellular fluid (and CSF) in composition with high Na and low K
• endolymph
  
  • fluid in the membranous labyrinth
  • similar in composition to intracellular fluid (low Na and high K)

Question 2

describe the semicircular canal

Answer 2

• the anterior, posterior and lateral semicircular canals are tubes within temporal bone (bony labyrinth)
• attached to the vestibule by an expanded ampulla
• the bony labyrinth is filled with perilymph
• the membranous labyrinth within is semicircular duct
• semicircular ducts contain endolymph

Question 3

describe the vestibule

Answer 3

• large irregular central cavity
• has the oval and round windows on the lateral wall that lead inot the adjacent cochlear canal
• represents the bony labyrinth
• membranous labyrinth within are:
  
  • utricle
  • saccule

Question 4

describe the cells of the membranous labyrinth

Answer 4

• sensory hair cells
  
  • project into endolymphatic space
• supporting cells

Question 5

describe the hair cells of vestibular labyrinths

Answer 5

• mechano-electric transducers
• rigid projections on their apical surfaces = stereocilia
  
  • hair bundle = rows of stereocilia
  • made of actin filaments
• increase in height in one particular direction
• single true cilium = kinocilium
  
  • kinocilium is located behind the tallest row of stereocilia
  • microtubules found within

Question 6

Answer 6

Question 7

describe the role of crista ampullaris in positioning

Answer 7

delfection of stereocilia during angular accleration of the head

Question 8

describe maculae

Answer 8

• contained within utricle and saccule
• sensors of gravity and linear acceleration of head
• cells of the epithelium face the endolymph
• gelatinous polysaccharide material over the epi. - otolithic membrane (OM)
• outer aspect of OM crystalline bodies of calcium carbonate and protein - otoconia

Question 9

describe the function of maculae in positioning

Answer 9

• deflection of stereocilia during linear acceleration of the head
  
  • ​head bent forward

Question 10

describe the cochlear duct (membranous labyrinth)

Answer 10

contains the spiral organ of Corti which lies on the basilar membrane

• vestibular membrane (Reissner’s): separates the scala media from the scala vestibule
• stria vascularis: responsible for the ionic composition of the endolymph
• organ of Corti (receptor for hearing): contains neuroepithelial hair cells - rests on the basilar membrane

Question 11

describe the organ of Corti

Answer 11

• presence of stereocilia
• tips of these hair cells embedded in tectorial membrane
• pillar cells occupies region between inner and outer hair cells, thus forming the inner tunnel

Question 12

Answer 12

Question 13

Answer 13

Question 14

Answer 14

Question 15

contrast conduction vs sensorineural deafness

Answer 15

• conduction deafness
  
  • pathway of sound conduction is blocked
• sensorineural deafness
  
  • destruction of nerve (sensory neuroepithelial) cells or central pathway to the brain