Identification and Morphology of Neuromuscular Spindles Found in the Human Orbicularis Oculi Muscles

Abstract

Abstract: : Purpose: To determine the number, identification, and morphological characteristics of neuromuscular spindles in the human orbicularis oculi muscles using the specific embryonic myosin heavy chain (MHC) immunochemical procedure. Methods: A prospective, randomized, experimental design was conducted on ten samples of freshly discarded human orbicularis oculi muscles taken from blepharoplasty patients. These samples were sectioned, prepared and processed using the various routine muscle biopsy tests, limited to the adenosine triphosphate fiber typing, NADH staining, and embryonic MHC immunochemical procedure. The embryonic MHC immunochemical procedure stains chain fibers strongly and bag fibers weakly-to-moderately in a dilution of 1:20. The MHC immunochemical procedure identified the presence of intrafusal fibers consistent with neuromuscular spindle (chain and bag) fibers. Each specimen was examined using light microscopy and electron microscopy. Each specimen measured 0.5 cm in size. Results: The numbers of chain fibers (n = 154) was sparse in the orbicularis oculi muscle compared to the number of bag fibers (n = 299) (ratio was 1:2). The average diameter of the chain fibers was (value +/- S.D.) 9.5 +/- 8.5 microns, and 18.9 +/- 15.6 microns for the bag fibers. The morphological characteristics of the human orbicularis oculi neuromuscular spindles were as follows: spindles lacked a specific capsule, were smaller in size, and less numerous than those found elsewhere in the body. Conclusion: This report of the occurrence of neuromuscular spindles in human orbicularis oculi muscles is the consequence of the enhanced sensitivity of the specific embryonic MHC immunochemical procedure.

Keywords: eyelid • molecular biology • shape and contour