Vestibular System Flashcards
What is the vestibular system, and what are its components?
- Part of the inner ear
- Fluid filled space in the petrous portion of the temporal bone
1. Bony Labyrinth
2. Membranous Labyrinth
What is the bony labyrinth, and what are its components?
- Perilymph filled space, lateral and posterior to the cochlea
1. Vestibule
2. Semicircular Canals
What is the Vestibule?
Small oval central cavity
- continuous with cochlea anteriorly and semicircular canals posteriorly
- Oval and round windows located here
- Contains the otolith organs
What are the semicircular canals?
- 3 canals projecting posterosuperior from the vestibule at right angles from one another
- At one end of each canal is a swelling, called the bony ampulla
- Contain the semicircular ducts
What is the membranous labyrinth and what are its components?
- Endolymph filled spaces suspended within the bony labyrinth
1. Otolith Organs
2. Semicircular Ducts
What are the otolith organs?
- 2 epithelial lined sacs located within the vestibule
1. utricle
2. saccue - Contains the maculae
What are maculae?
- Location of the receptors for translational head movements and orientation of the head relative to gravity
- Where transduction occurs
Describe the macula of the utricle.
- Horizontally placed
- Concerned with motion in the horizontal plane
Describe the macula of the saccule
- Vertically placed
- Concerned with motion in the vertical plane
What are the semicircular ducts?
- Epithelial lined ducts
- Project from the utricle
- located within the semicircular canals
- Contains the membranous ampullae
What are the membranous ampullae and where are they located?
- Location of the receptors for rotational head movements
- Located within the bony ampullae at one end of each semicircular duct.
What is meniere syndrome?
- Disruption of normal endolymph volume
- Abnormal distention of the membranous labyrinth
- Vertigo, tinnitus, hearing loss, and nausea occurs.
What are the maculae and membranous ampullae analagous to in the auditory and visual systems?
- Organ of corti
- Neural Retina
What are the components of the maculae and membranous ampullae?
- Hair Cells
2. Gelatinous Layers
Describe the structure of the hair cells in the vestibular system.
- Hair buncle with stereocilia and a single longer kinocilium
- Stereocilia are arranged in rows, graded by height, tallest next to the kinocilium.
- Tip links: extend from tip of each stereocilium to the next tallest neighbor
What are the types of hair cells in the vestibular system?
- Type I- Pear shaped and innervated by terminals of afferent vestibular cells
- Type II- Columnar shaped and innervated by simple terminals of afferent vestibular cells
What are the two types of gelatinous layers in the maculae and membranous ampullae?
- Otolithic Membrane
2. Cupula
What is the structure and function of the otolithic membrane?
S: Covered by calcium carbonate crystals (otoconia), which are 3 times as dense as endolymph, and not displaced by normal endolymph movements
F: Envelopes the stereocilia and kinocilium of the maculae
What is the structure and function of the Cupula?
S: Attached to the floor, roof, and walls of the membranous ampullae. Same specific density as that of the endolymph.
F: Envelopes the stereocilia and kinocilium of the membranous ampullae
What is the striola?
A curved depression on the otolithic membrane that bisects the maculae.
How are hair cells on the utricular macula organized?
Polarized so that the kinocilium is always on the side toward the striola.
How are hair cells on the saccular macula organized?
Polarized so that the kinocilium is always on the side away from the striola.
What are crista?
- A ridge that the hair cells are embedded in
- Perpendicular to the long axis of the duct
- Located in the membranous ampullae