Special Senses (Auditory) Flashcards
Parts of the ear:
- Outer (external) ear
- Middle ear (tympanic cavity)
- Middle Ear or Tympanic Cavity
- Medial Boundary
- Lateral Boundary
- Anterior Boundary
- Posterior Boundary
- Inner (internal) ear (labyrint)
o Pinna or auricle
o External acoustic meatus
o Tympanic Membrane or Eardrum
Outer (external) ear
➢ Shell-shaped structure surrounding the auditory canal opening
Pinna or Auricle
➢ A short narrow chamber about 1 inch long by ½ inch wide
➢ Curved into temporal bone of the skull
➢ Skin of walls lined with ceruminous glands which secretes a waxy yellow substance called ear wax, or cerumen
External Auditory Canal
➢ A thin membrane separating outer from middle ear
Tympanic Membrane or Eardrum
o Ossicles (malleus, incus stapes)
o Tensor tympani, stapedius
Middle ear (tympanic cavity)
➢ A small, air filled cavity within the temporal bone
Middle Ear or Tympanic Cavity
➢ A bony wall with 2 openings:
o Oval window
o Round window
Medial Boundary
➢ Tympanic membrane with handle of the malleus attached
Lateral Boundary
➢ Eustachian tube (connects middle ear and nasopharynx)
Anterior Boundary
➢ Mastoid process
o Ossicles in the Middle Ear
Posterior Boundary
➢ Malleus (hammer) attached to tympanic membrane
➢ Incus – anvil
➢ Stapes – stirrups, presses on the oval window of the inner ear
Ossicles in the Middle Ear
➢ Composed of 2 parts:
o Bony Labyrinth
o Membranous Labyrinth
Inner (internal) ear (labyrinth)
➢ Wall is bony – temporal bone
➢ Fluid inside is perilymph (one of the two types of cochlear fluids, the other being endolymph)
➢ Made up of:
▪ Cochlea
▪ Vestibule
▪ 3 semicircular canals
Bony Labyrinth
made up of scala vestibuli and tympani;
concerned with hearing
Cochlea
concerned with static equilibrium
Vestibule
concerned with dynamic equilibrium
3 semicircular canals
➢ Found inside the bony labyrinth
➢ Wall is fibrous
➢ Fluid inside is endolymph (fluid contained in the membranous labyrinth of the inner ear)
➢ Made up of:
▪ Scala media
▪ Utricle & Saccule
▪ 3 semicircular ducts
Membranous Labyrinth
inside bony cochlea
Scala media
inside bony vestibule
Utricle & Saccule
inside the semicircular canal
3 semicircular ducts
- Receptor for hearing
- Found in the cochlea
Organ of Corti
- A spiral bony canal turning 2 ¾ around a central bony axis (modiolus)
- A spial bony projection from modiolus (spiral lamina) makes also a 2 ¾ turns.
- Scala vestibuli and tympani contain perilymph. They communicate in heliotrema
- Scala media contains endolymph
o Incompletely divides the bony cochlea
➢ Scala vestibuli
➢ Scala tympani
Cochlea
- Composed of five filaments embedded in gelatinous matrix rich in mucopolysaccharides
- Secreted at the upper surface of interdental cells
Tectorial membrane
Hearing loss of any degree
Deafness
2 types of deafness
- Conduction Deafness
- Sensorineural Deafness
➢ Temporary or permanent
➢ Results when something interferes with conduction of sound vibrations to the fluids of the inner ear
➢ Involves diseases of external and middle ear
o Impacted Cerumen
o Otosclerosis
o Rupture of Eardrum
o Otitis Media
Conduction Deafness
➢ Results from degeneration or damage to receptor cells to cochlear nerve, or to neurons of auditory cortex
Factors:
o Old age
o Extended listening to excessively loud sounds
o Intake of ototoxic drugs like streptomycin, quinine, aspirin
Sensorineural Deafness
this are the Test to distinguish sensorineural from conduction deafness
- Weber’s Test
- Rinne’s Test
➢ The base of the vibrating tuning fork is applied in the midline
Result for:
o Normal Individual - sound appears to be in the midline
o Conduction Deafness - sound appears louder in the affected ear
o Sensorineural Deafness - sound appears louder in the normal ear
Weber’s Test
➢ The base of the tuning fork is placed over the mastoid process of the skull
➢ When it can no longer be heard, it is removed and then is held in front of the ear
Result for:
o Normal Individual - continues to hear by air conduction after bone conduction ceases; air conduction is greater than bone conduction
o Conduction Deafness - bone is greater than air conduction
o Sensorineural Deafness - both are diminished but air conduction remains better than bone conduction
- Rinne’s Test
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