title: [Proprioception of extra-ocular muscles in the human: on the morphology of muscle spindles].
abstract: BACKGROUND
  Increasing importance is attributed to the proprioceptive innervation of extraocular muscles for the development of binocular vision. In the literature, data on proprioceptors in human extraocular muscles are rare and inconsistent. Therefore a detailed morphological analysis of spindles in human extraocular muscles appeared indicated.
  
  
  METHODS
  Complete serial sections of all extraocular muscles of 3 human individuals, 67, 72, and 83 years of age, were alternately impregnated with silver, stained following Mowry and immunohistochemically stained for S100 or PGP 9.5. Distal parts of extraocular muscles from multiorgan donors, 2, 17, and 34 years of age, were prepared for electron microscopy.
  
  
  RESULTS
  Spindles contained 1 to 18 intrafusal muscle fibers, 55% of which were nuclear chain fibers, 2% nuclear bag fibers, and 43% fibers exhibiting the same morphological features as extrafusal fibers. The latter had been previously described as "anomalous fibers" (Ruskell). This intrafusal type exclusively occurs in human extraocular muscle spindles. Ultrastructural analysis revealed morphologically normal sensory terminals on all 3 types of intrafusal fibers. Findings in a two-year-old individual were similar to those in aged individuals.
  
  
  CONCLUSIONS
  Spindles in human extraocular muscles are specifically structured. Their special morphological features are also present during the development of binocular vision. Spindles are supposed to play a role in the (fine) control of eye movements.
authors.affiliation: Univ.-Klinik f. Augenheilkunde und Optometrie Wien.
authors.forename: J R
authors.initials: JR
authors.lastname: Lukas
authors.forename: R
authors.initials: R
authors.lastname: Blumer
authors.forename: M
authors.initials: M
authors.lastname: Aigner
authors.forename: M
authors.initials: M
authors.lastname: Denk
authors.forename: I
authors.initials: I
authors.lastname: Baumgartner
authors.forename: R
authors.initials: R
authors.lastname: Mayr
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D009470:Muscle Spindles / Q000033:anatomy & histology*; D009801:Oculomotor Muscles / Q000294:innervation*; D011434:Proprioception / Q000502:physiology*; D012016:Reference Values; D015348:Vision, Binocular / Q000502:physiology