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Lacrimal ducts
Introduction
Overview
Overview
The lacrimal canaliculi, also known as the lacrimal canals or lacrimal ducts, are the small channels in each eyelid that commence at minute orifices, termed puncta lacrimalia, on the summits of the papillæ lacrimales, seen on the margins of the lids at the lateral extremity of the lacus lacrimalis.
- The superior duct, the smaller and shorter of the two, at first ascends, and then bends at an acute angle, and passes medialward and downward to the lacrimal sac.
- The inferior duct at first descends, and then runs almost horizontally to the lacrimal sac.
At the angles they are dilated into ampullæ; their walls are dense in structure and their mucous lining is covered by stratified squamous epithelium, placed on a basement membrane.
Outside the latter is a layer of striped muscle, continuous with the lacrimal part of the Orbicularis oculi; at the base of each lacrimal papilla the muscular fibers are circularly arranged and form a kind of sphincter.