inner ear

Examples of inner ear in the following topics:

• Vestibulocochlear (VIII) Nerve

  • This is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain.
  • It emerges from the pons and exits the inner skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone.
  • The cochlear nerve travels away from the cochlea of the inner ear where it starts as the spiral ganglia.
  • The vestibular nerve travels from the vestibular system of the inner ear.
  • An illustration of the inner ear showing its semicircular canal, hair cells, ampulla, cupula, vestibular nerve, and fluid.

• Development of Hearing and Balance

  • The human inner ear develops during week four of embryonic development from the auditory placode, a thickening of the ectoderm that gives rise to the bipolar neurons of the cochlear and vestibular ganglions.
  • Describe the development of the inner ear for hearing and balance

• Sensory Modalities

  • The ossicles (three tiny bones in the middle ear) pass the vibrations to the fluid-filled cochlea (a spiral, shell-shaped auditory organ of the inner ear).
  • The organ of equilibrioception is the vestibular labyrinthine system found in both of the inner ears.

• Classification of Receptors by Stimulus

  • During hearing, mechanoreceptors in hair cells of the inner ear detect vibrations conducted from the eardrum.

• Classification of Receptors by Location

  • Our skin includes touch and temperature receptors, and our inner ears contain sensory mechanoreceptors designed for detecting vibrations caused by sound or used to maintain balance.

• Overview of Sensation

  • Mechanoreceptors in the inner ear turn vibration motion into electrical nerve pulses.
  • The vibrations are mechanically conducted from the eardrum through a series of tiny bones to hair-like fibers in the inner ear that detect the mechanical motion of the fibers.

• Brief Overview of Cranial Nerves

  • The vestibulocochlear nerve (VIII): This is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain.
  • The glossopharyngeal nerve (IX): This nerve receives sensory information from the tonsils, the pharynx, the middle ear, and the rest of the tongue.

• Vagus (X) Nerve

  • The spinal trigeminal nucleus: Receives information about deep/crude touch, pain, and temperature of the outer ear, the dura of the posterior cranial fossa, and the mucosa of the larynx.
  • It also has some afferent fibers that innervate the inner (canal) portion of the outer ear, via the auricular branch (also known as Alderman's nerve) and part of the meninges.
  • This explains why a person may cough when tickled on the ear (such as when trying to remove ear wax with a cotton swab).

• Tissue Development

  • This then becomes a blastocyst, consisting of an outer layer called a trophoblast, and an inner cell mass called the embryoblast.
  • The inner cell mass initially has two layers: the hypoblast and epiblast.
  • Cells migrating inward along the primitive gut form the inner layer of the gastrula, which develops into the endoderm.
  • It also forms the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas; the epithelium of the auditory tube and ear cavity; the trachea, bronchi, and air cells of the lungs; the urinary bladder and part of the urethra; and the follicle lining of the thyroid gland and thymus.
  • Image illustrates the types of cells produced by the endoderm (inner germ layer) of the developing embryo.

• Impacted Cerumen

  • Earwax, or cerumen, is a yellowish waxy substance secreted in the ear canal which can affect hearing if produced excessively.
  • Excessive earwax may impede the passage of sound in the ear canal, causing conductive hearing loss.
  • Cerumen is produced in the outer third of the cartilaginous portion of the human ear canal.
  • Movement of the jaw helps the ears' natural cleaning process.
  • A curette method is more likely to be used by otolaryngologists when the ear canal is partially occluded and the material is not adhering to the skin of the ear canal.