Overview of the lacrimal canaliculus in microscopic cross-section.

Although many illustrations have been published seeking to explain the anatomy of the lacrimal canaliculus and its surroundings, to our knowledge, no micrograph showing the total length of the lacrimal canaliculus has ever been displayed. Here, we present a clear microscopic cross-section of the total length of an upper lacrimal canaliculus, except for the vertical part. A winding path was found in part of the canaliculus. The common canaliculus opened into the lacrimal sac almost perpendicularly and was covered by solid fibrous tissue. The transition between squamous cell epithelium and columnar epithelium did not always take place at the opening. There were superficial goblet cells, mucous secretory glands and intraluminal debris in the distal part of the canaliculus, including the common canaliculus, where the lining consisted of columnar epithelium. The clear overview of the structures presented here should be helpful in the treatment of the lacrimal canaliculus.