The lacrimal sac and nasolacrimal duct are surrounded by a wide cavernous system of veins and arteries
comparable to a cavernous body. The present study aimed to demonstrate the ultrastructure of the nervous
tissue and the localisation of neuropeptides involved in the innervation of the cavernous body, a topic not
previously investigated. Different S-100 protein antisera, neuronal markers (neuron-specific enolase, anti-
200 kDa neurofilament), neuropeptides (substance P, neuropeptide Y, calcitonin gene-related peptide,
vasoactive intestinal polypeptide) and the neuronal enzyme tyrosine hydroxylase were used to demonstrate
the distribution pattern of the nervous tissue. The ultrastructure of the innervating nerve fibres was also
examined by means of standard transmission electron microscopy.
The cavernous body contained specialised arteries and veins known as barrier arteries, capacitance veins,
and throttle veins. Perivascularly, the tissue was rich in myelinated and unmyelinated nerve fibres in a
plexus-like network. Small seromucous glands found in the region of the fundus of the lacrimal sac were
contacted by nerve fibres forming a plexus around their alveoli. Many nerve fibres were positive for S-100
protein (S 100), neuron-specific enolase (NSE), anti-200 kDa neurofilament (RT 97), calcitonin gene-related
peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY). Vasoactive
intestinal polypeptide (VIP) immunoreactivity was only demonstrated adjacent to the seromucous glands.
Both the density of nerve fibres as well as the presence of various neuropeptides emphasises the neural
control of the cavernous body of the human efferent tear ducts. By means of this innervation, the specialised
blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as
effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow.
Related functions such as a role in the occurrence of epiphora related to emotional responses are relevant.
Moreover, malfunction in the innervation of the cavernous body may lead to disturbances in the tear
outflow cycle, ocular congestion or total occlusion of the lacrimal passages.