II. Anatomy: Vestibular Structures

  1. Semicircular canals
    1. Monitors head rotation and spatial positioning
    2. Three semicircular canals with endolymph fluid filled ampullae
      1. Canals lie at right angles to one another
      2. One for each direction (e.g. X,Y and Z axis)
      3. Fluid filled canals contain crista ampullaris
        1. Crista ampullaris is a sensory organ detecting sudden head rotation, acceleration and deceleration
        2. Hair cells within the crista ampullaris detect fluid motion
        3. Hair cells generate an impulse that is transmitted centrally via Vestibular Nerve (CN 8)
  2. Otolithic organs
    1. Utricle
      1. Contains otoliths (small stones) that settle with position changes
      2. Detects horizontal linear movement and Head Tilting
    2. Sacule
      1. Smaller, more globular organ without utricle communication
      2. Detects vertical linear movement (e.g. gravity)
    3. Both Utricle and Sacule contain a Macula (sack)
      1. Macula contains thick, gelatinous material and otoliths
      2. Otoliths (statoconia) are Calcium Carbonate crystals that move with gravity and head movement
      3. Hair cells within the Macula detect static head position as well as head movement
  3. Perilymphatic fluid
    1. Surrounds vestibular apparatus (semicircular canals and otolithic organs)
    2. Communicates with the perilymph of the Cochlea (from oval window to round window)
    3. Communicates with perilymphatic duct (and the subarachnoid space)

III. Anatomy: Neurologic Structures

  1. Cranial Nerve 8 (two tracts)
    1. Vestibular tract carries signals from the utricle and sacule
    2. Cochlear tract carries signals from the Hearing apparatus in the Cochlea
  2. Vestibular nucleii
    1. Located in the pons and Medulla and receive input from the respective tracts of Cranial Nerve 8
    2. Transmit signals to the rest of the Cerebrum, Cerebellum and spinal cord
      1. Combines with other inputs (e.g. occiptal lobe, dorsal columns)
  3. Medial Longitudinal Fasciculus and Oculomotor Nucleus
    1. Brainstem fiber tracts that connect with the Oculomotor Nucleus
      1. Carry information directing eye movement
    2. Connects with CN 3, CN 4, and CN 6 for eye motor activity
      1. Also Synapses with CN 8 for head position input related to eye saccades

IV. Anatomy: Vascular Structures

  1. See Vertebro-Basilar CVA
  2. Posterior Circulation via the vertebrobasilar system
  3. Vertebral arteries
    1. Two arteries ascend in parallel from the subclavian artery via each transverse foramen
    2. Join to form the Basilar Artery
    3. Branches
      1. Posterior Inferior Cerebellar Artery (see PICA CVA)
      2. Anterior Spinal Artery
  4. Basilar Artery
    1. Arises from the joining of the two Vertebral arteries
    2. Courses anteriorly to join with the Anterior Circulation via the Circle of Willis
    3. Branches
      1. Anterior Inferior Cerebellar Artery
      2. Superior Cerebellar Artery

V. Anatomy: Images

  1. entVestibularGrayBB900.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. entVestibularGrayBB901.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  3. entEarVestibularGrayBB920.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  4. entEarVestibularXsGrayBB921.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  5. entVestibularIllustrationGrayBB924.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  6. entEarVestibularTransverseXsGrayBB927.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

VI. References

  1. Goldberg (2014) Clinical Physiology, Medmaster, Miami, p. 118-9
  2. Ondrejka (2014) Crit Dec Emerg Med 28(10): 11-7

Images: Related links to external sites (from Bing)

Related Studies

Ontology: Vestibular Labyrinth (C1735318)

Definition (NCI) The central cavity of the osseous labyrinth.
Definition (PSY) Major organ of equilibrium which acts as a sensory receptor that detects the position and changes in the position of the head in space.
Definition (CSP) structures of the inner ear concerned with reception and transduction of stimuli of equilibrium; they include the semicircular canals, the utricle, and the saccule.
Definition (MSH) An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony COCHLEA anteriorly, and SEMICIRCULAR CANALS posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the STAPES of the MIDDLE EAR.
Concepts Body Part, Organ, or Organ Component (T023)
MSH D014722
SnomedCT 181188003
English Apparatus, Vestibular, Vestibular Apparatus, vestibular apparatus, Labyrinth Vestibules, Labyrinth, Vestibular, Labyrinths, Vestibular, Vestibules, Labyrinth, Vestibular Labyrinths, Vestibule, Labyrinth, Labyrinth Vestibule, Vestibular Labyrinth, vestibular labyrinth, Vestibular labyrinth, Labyrinthus vestibularis, Vestibulum Auris, Vestibules, Ear, Ear Vestibule, Vestibule, Ear, Vestibule of Ear, Ear Vestibules, Vestibule, Vestibule of the Ear, Vestibular apparatus, Vestibular apparatus (body structure)
French Appareil vestibulaire, Système vestibulaire labyrinthique, Vestibule labyrinthique, Labyrinthe vestibulaire, Vestibule de l'oreille interne, Vestibulum auris
Swedish Vestibularapparat
Czech vestibulární aparát
Portuguese Vestíbulo do Labirinto, Sistema Vestibular
Spanish Vestíbulo del Laberinto, aparato vestibular (estructura corporal), aparato vestibular, Aparato Vestibular
Finnish Sisäkorvan eteinen
Italian Vestibolo, Apparato vestibolare, Labirinto vestibolare
Japanese 前庭, 前庭(迷路), 前庭迷路, 前庭器
Polish Narząd równowagi, Aparat przedsionkowy, Narząd przedsionkowy błędnika, Narząd przedsionkowy
Norwegian Vestibulum, Forgården, Vestibulum auris, Apparatus vestibularis
German Apparatus vestibularis, Gleichgewichtsorgan, Statisches Organ, Vestibulum

Ontology: Vestibular functions (C2370946)

Definition (ICF) Sensory functions of the inner ear related to position, balance and movement.
Definition (ICF-CY) Sensory functions of the inner ear related to position, balance and movement.
Concepts Physiologic Function (T039)
English Vestibular functions, unspecified, Vestibular functions