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Encapsulated Ruffini‐like endings in human lumbar facet joints
Author(s) -
VANDENABEELE F.,
CREEMERS J.,
LAMBRICHTS I.,
LIPPENS P.,
JANS M.
Publication year - 1997
Publication title -
journal of anatomy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 118
eISSN - 1469-7580
pISSN - 0021-8782
DOI - 10.1046/j.1469-7580.1997.19140571.x
Subject(s) - anatomy , axolemma , basal lamina , free nerve ending , mechanoreceptor , ultrastructure , vesicle , cell type , capsule , electron microscope , chemistry , biophysics , pathology , biology , medicine , sensory system , neuroscience , cell , membrane , physics , myelin , central nervous system , biochemistry , botany , optics
The innervation of the human lumbar facet joint capsule was studied by light and electron microscopy. Small numbers of encapsulated corpuscular endings were identified in the dense fibrous layer. Clusters of 2 types of endings were found: small cylindrical corpuscles (type 1) and large fusiform corpuscles (type 2). The corpuscles were classified structurally as Ruffini‐type endings. The 1st type was predominant and characterised by a compartmentalised receptor complex, a thin perineurial capsule and a narrow subcapsular space. The 2nd type was characterised by a thicker perineurial capsule, a ‘spindle‐like’ receptive complex, and an extensive subcapsular space with capillaries and concentrically oriented fibroblast‐like cells. Both types of endings were innervated mainly by thinly myelinated group III (A delta) and unmyelinated group IV (C) nerve fibres that branched and terminated in the receptor complex. Their sensory endings were intimately related to the collagen fibre bundles as multiple enlarged axonal segments (‘beads’) with ultrastructural features which were characteristic of receptive sites: an accumulation of mitochondria and vesicles, and ‘bare’ areas of axolemma lacking a Schwann cell investment but covered by a thin basal lamina. Some beads in the 2nd type of ending contained granular vesicles, 30–60 mm in diameter, resembling sympathetic nerve endings. Small diameter collagen fibrils situated within multilayered basal laminae were found among the multiple receptive sites in the receptive complex in both types of ending. Their possible functional significance in mechanoreception is discussed. Particular attention has been given to their apparent variable orientation to the mechanoreceptive site.