title: The cavernous body of the human efferent tear ducts: function in tear outflow mechanism.
abstract: OBJECTIVE
  To determine the structure and function of a system of large blood vessels integrated in the bony canal between the orbit and the inferior nasal duct.
  
  
  METHODS
  Thirty-one dissected lacrimal systems of adults were analyzed by using 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 filled by a plexus of wide-lumened veins and arteries. The vascular system is embedded in the wall of the lacrimal sac and nasolacrimal duct and is connected to the cavernous tissue of the inferior turbinate. Three types of blood vessels can be distinguished inside the vascular tissue that surrounds the lumen of the lacrimal passage: barrier arteries, capacitance veins, and throttle veins.
  
  
  CONCLUSIONS
  The surrounding vascular plexus of the lacrimal sac and nasolacrimal duct is comparable to a cavernous body. While regulating the blood flow, the specialized blood vessels permit opening and closing of the lumen of the lacrimal passage, effected by the bulging and subsiding of the cavernous body, and at the same time regulate tear outflow. Other functions such as drainage of absorbed tear fluid components and a role in immunologic response are under discussion as well. Malfunctions in the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion, or total occlusion of the lacrimal passages. Variations in the conditions for swelling of the cavernous tissue may have led to the (mistaken) description of valves in the lacrimal passage.
authors.affiliation: Department of Anatomy, Christian Albrecht University of Kiel, Germany. fpaulsen@anat.uni-kiel.de
authors.forename: F P
authors.initials: FP
authors.lastname: Paulsen
authors.forename: A B
authors.initials: AB
authors.lastname: Thale
authors.forename: U J
authors.initials: UJ
authors.lastname: Hallmann
authors.forename: U
authors.initials: U
authors.lastname: Schaudig
authors.forename: B N
authors.initials: BN
authors.lastname: Tillmann
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001808:Blood Vessels / Q000502:physiology* / Q000648:ultrastructure; D016319:Corrosion Casting; D005260:Female; D006801:Humans; D007765:Lacrimal Apparatus / Q000098:blood supply* / Q000648:ultrastructure; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D009301:Nasolacrimal Duct / Q000098:blood supply / Q000648:ultrastructure; D009915:Orbit / Q000098:blood supply* / Q000648:ultrastructure; D013666:Tears / Q000378:metabolism*