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Histological analysis of sensory receptors in human extraocular muscles
Author(s) -
BRUENECH JR,
KJELLEVOLD HAUGEN IB
Publication year - 2008
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2008.5122.x
Subject(s) - extraocular muscles , proprioception , muscle spindle , anatomy , sensory system , biology , mechanoreceptor , vestibular system , afferent , neuroscience
Purpose Recent publications have promoted the view that tendon receptors at the distal insertion of extraocular muscles (EOMs) provide more adequate proprioception than the muscle spindles, yet some uncertainty remains. The purpose of this study was therefore to analyse the morphological features of the muscle spindles and their potential proprioceptive capacity. Methods Samples of human EOMs were selected from stock and all sections containing muscle spindles were selected for further analysis. The age of the subjects ranged from 6 months to 90 years and both sexes were included. No previous history of binocular anomalies or neuromuscular disease had been recorded. An image analysis system (Imaris Imageaccess) was attached to a light microscope (Nikon Optiphot) in order to obtain a more detailed analysis. Results Digital three dimensional reconstructions of the most prominent morphological features were obtained from serial sections of 35 spindles. These features included narrow periaxial spaces, fragmented intrafusal fibres and other peculiar features which could potentially interfere with the functional principals upon which this type of mechanoreceptor is based. The digital reconstruction provided additional information about variations in spindle shape which most likely would have been missed by conventional light microscopic observations. Conclusion The proprioceptive capacity of the muscle spindles in human extraocular muscles has previously been questioned based on the presence of several peculiar morphological features. The current study confirmed these observations and has added credence to the notion that the muscle spindle in human EOMs in not the main source of proprioception. A similar study of the tendon receptors is now in progress.