The Capsular Sleeve of Muscle Spindles in Mouse and Man with Special Reference to the Cytoskeleton
Muscle spindles are enveloped by a capsular sleeve that is endowed with two cellular portions, an outer and inner capsule. Both portions of the capsule contribute to a permeability barrier which is impervious at the equator yet leaky at its distal ends to vascularly infused tracers (Dow et al., 1980). In addition to its protective role in sequestering the sensory regions of intrafusal fibers, the capsule must be designed to accommodate alterations in shape and repetitive changes in length that normally occur during muscular shortening. Bridgeman and Eldred (1984) compared the capsule to a double-ended squeeze bulb, and postulated a pressure sensitive role in response to subtle fluxes in intramuscular pressure. To test this hypothesis, the mechanical properties inherent in the capsule and its contractile ability need to be clarified.
KeywordsMuscle Spindle Intramuscular Pressure Intrafusal Fiber Intrafusal Muscle Outer Capsule
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