membranous labyrinth

Examples of membranous labyrinth in the following topics:

• Development of Hearing and Balance

  • The auditory vesicle will give rise to the utricluar and saccular components of the membranous labyrinth.
  • Beginning in the fifth week of development, the auditory vesicle also gives rise to the cochlear duct, which contains the spiral organ of Corti and the endolymph that accumulates in the membranous labyrinth.
  • The basilar membrane separates the cochlear duct from the scala tympani, a cavity within the cochlear labyrinth.
  • The hair cells develop from the lateral and medial ridges of the cochlear duct, which together with the tectorial membrane make up the organ of Corti.

• Transduction of Sound

  • The structures of the inner ear are found in the labyrinth, a bony, hollow structure that is the most interior portion of the ear.
  • Above the basilar membrane is the tectorial membrane.
  • The hair cells are arranged on the basilar membrane in an orderly way.
  • Lower frequencies travel farther along the membrane before causing appreciable excitation of the membrane.
  • When sound waves produce fluid waves inside the cochlea, the basilar membrane flexes, bending the stereocilia that attach to the tectorial membrane.

• Geometric Symbolism

  • Similar to the mandala, the labyrinth is a geometric pattern often used to symbolize a journey to the center or to the divine.
  • A labyrinth, though similar in appearance to a child's maze, consists of a single, non-branching path which leads to the center.
  • Labyrinths can be thought of as symbolic forms of pilgrimage.
  • Many people could not afford to travel to holy sites and lands so labyrinths and prayer substituted for such travel.
  • In prehistoric times, labyrinths may have also served as traps for malevolent spirits or as defined paths for ritual dances.

• Membrane Fluidity

  • The mosaic nature of the membrane, its phospholipid chemistry, and the presence of cholesterol contribute to membrane fluidity.
  • There are multiple factors that lead to membrane fluidity .
  • First, the mosaic characteristic of the membrane helps the plasma membrane remain fluid.
  • It lies alongside the phospholipids in the membrane and tends to dampen the effects of temperature on the membrane.
  • Explain the function of membrane fluidity in the structure of cells

• Injuring the Plasma Membrane

  • Several types of antimicrobial drugs function by disrupting or injuring the plasma membrane.
  • The plasma membrane or cell membrane is a biological membrane that separates the interior of all cells from the outside environment.
  • The plasma membrane is selectively permeable to ions and organic molecules.
  • The membrane basically protects the cell from outside forces.
  • Diagram of a typical gram-negative bacterium, with the thin cell wall sandwiched between the red outer membrane and the thin green plasma membrane.

• Components of Plasma Membranes

  • The plasma membrane protects the cell from its external environment, mediates cellular transport, and transmits cellular signals.
  • The plasma membrane (also known as the cell membrane or cytoplasmic membrane) is a biological membrane that separates the interior of a cell from its outside environment.
  • The primary function of the plasma membrane is to protect the cell from its surroundings.
  • The membrane also maintains the cell potential.
  • The cell employs a number of transport mechanisms that involve biological membranes:

• Selective Permeability

  • Plasma membranes are asymmetric: the interior of the membrane is not identical to the exterior of the membrane.
  • On the interior of the membrane, some proteins serve to anchor the membrane to fibers of the cytoskeleton.
  • This adds considerably to the selective nature of plasma membranes.
  • Polar substances present problems for the membrane.
  • The exterior surface of the plasma membrane is not identical to the interior surface of the same membrane.

• Osmosis

  • Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes.
  • Semipermeable membranes, also termed selectively permeable membranes or partially permeable membranes, allow certain molecules or ions to pass through by diffusion.
  • While diffusion transports materials across membranes and within cells, osmosis transports only water across a membrane.
  • The semipermeable membrane limits the diffusion of solutes in the water.
  • On both sides of the membrane the water level is the same, but there are different concentrations of a dissolved substance, or solute, that cannot cross the membrane (otherwise the concentrations on each side would be balanced by the solute crossing the membrane).

• The Plasma Membrane and the Cytoplasm

  • Despite differences in structure and function, all living cells in multicellular organisms have a surrounding plasma membrane (also known as the cell membrane).
  • Cholesterol, also present, contributes to the fluidity of the membrane.
  • This structure causes the membrane to be selectively permeable.
  • In the case of the plasma membrane, only relatively small, non-polar materials can move through the lipid bilayer (remember, the lipid tails of the membrane are nonpolar).
  • Explain the structure and purpose of the plasma membrane of a cell

• Membrane Potentials as Signals

  • Membrane potential (also transmembrane potential or membrane voltage) is the difference in electrical potential between the interior and the exterior of a biological cell.
  • The membrane serves as both an insulator and a diffusion barrier to the movement of ions.
  • Ion transporter/pump proteins actively push ions across the membrane to establish concentration gradients across the membrane, and ion channels allow ions to move across the membrane down those concentration gradients, a process known as facilitated diffusion.
  • The membrane potential has two basic functions.
  • Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential that causes electric current to flow rapidly to other points in the membrane.