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Roland Blumer, Richard Wasicky, Peter Christian Brugger, Wolfram Hoetzenecker, Waltraut Lydia Margarethe Wicke, Julius-Robert Lukas; Number, Distribution, and Morphologic Particularities of Encapsulated Proprioceptors in Pig Extraocular Muscles. Invest. Ophthalmol. Vis. Sci. 2001;42(13):3085-3094. doi: https://doi.org/.
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purpose. To analyze qualitatively and quantitatively the total complement of
encapsulated proprioceptors (Golgi tendon organs [GTOs] and
neuromuscular spindles) in pig extraocular muscles (EOMs).
methods. EOMs of four pigs of different ages were prepared for light microscopic
histochemical and immunohistochemical analysis and for transmission
results. GTOs and muscle spindles were numerous in pig EOMs. GTOs were found to
be distributed in aponeurotic expansions of the distal and proximal EOM
tendons, being more numerous in the distal aponeurosis than in the
proximal aponeurosis. The total number of GTOs was higher in the recti
EOMs (100–128) than in the oblique EOMs (45–61). Spindles were
distributed over the entire muscle length. In each EOM the number of
muscle spindles (142–333) exceeded those of GTOs. The morphology of
the GTOs was variable. In addition to collagen bundles, approximately
one third of the GTOs contained intracapsular muscle fibers that
resembled the multiply innervated fiber type. Intracapsular muscle
fibers entered the poles of the GTOs and either terminated inside the
receptors in collagen bundles or exited the GTOs at the opposite poles.
Nerve terminals were numerous in each GTO and established intimate
contacts with collagen fibrils.
conclusions. Most structural particularities formerly observed in GTOs of rhesus
monkey and sheep EOMs are also present in GTOs of pig EOMs. The high
number of GTOs with their typical nerve terminals indicates functional
importance. During muscle activity, afferent signals from GTOs and
muscle spindles may provide sufficient information about eye
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