The cavernous body of the human efferent tear ducts: Function in tear outflow mechanism

PURPOSE. TO determine the structure and function of a system of large blood vessels integrated in the bony canal between the orbit and the inferior na sal duct. METHODS. Thirty-one dissected lacrimal systems of adults were analyzed by u sing gross anatomy, histology, and electron microscopy as well as corrosion vascular casts. RESULTS. More than two thirds of the bony canal between orbit and inferior nasal duct is fixed by a plexus of wide-lumened veins and arteries. The vas cular system is embedded in the wall of the lacrimal sac and nasolacrimal d uct and is connected to the cavernous tissue of the inferior turbinate. Thr ee types of blood vessels can be distinguished inside the vascular tissue t hat surrounds the lumen of the lacrimal passage: barrier arteries, capacita nce veins, and throttle veins. CONCLUSIONS. The surrounding vascular plexus of the lacrimal sac and nasola crimal duct is comparable to a cavernous body. While regulating the blood f low, the specialized blood vessels permit opening and closing of the lumen of the lacrimal passage, effected by the bulging and subsiding of the caver nous body, and at the same time regulate tear outflow. Other functions such as drainage of absorbed tear fluid components and a role in immunologic re sponse are under discussion as well. Malfunctions in the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion, or tota l occlusion of the lacrimal passages. Variations in the conditions for smel ling of the cavernous tissue may have led to the (mistaken) description of valves in the lacrimal passage.