DEMONSTRATION OF NERVE-FIBERS IN HUMAN ACCESSORY LACRIMAL GLANDS

To provide morphologic evidence for the innervation of accessory lacri mal glands, glands were biopsied and examined using standard transmiss ion electron microscopic techniques. Non-myelinated nerve fibers were found in the connective tissue between the glandular epithelia where t hey made contact with glandular epithelial cells, myoepithelial cells, vascular endothelial cells, plasma cells and fibroblasts. The distanc es measured between axons and target cells ranged from 30 to 130 nm. W here nerve fibers approached cells sustaining a basement membrane, the ir basement membranes fused to form a discrete unit resembling so-call ed 'synapses a distance'. Cells with no basement membrane were situate d in direct contact with the basement membrane of a nerve fiber. Singl e axons were identified between glandular epithelial cells and cells o f intralobular ducts. Most of these axons contained many small clear v esicles and a few large, dense core vesicles, a finding considered typ ical of cholinergic parasympathetic nerve fibers. In addition, one of the axons identified contained small dense core vesicles typical of sy mpathetic nerve fibers. Human accessory lacrimal glands are therefore definitely innervated, with parasympathetic structures morphologically prevailing over sympathetic structures.