S: (n) orifice, opening, porta (an aperture or hole that opens into a bodily cavity) "the orifice into the aorta from the lower left chamber of the heart"
S: (n) duct, epithelial duct, canal, channel (a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance) "the tear duct was obstructed"; "the alimentary canal"; "poison is released through a channel in the snake's fangs"
S: (n) sinusoid (tiny endothelium-lined passages for blood in the tissue of an organ)
S: (n) carpal tunnel (a passageway in the wrist through which nerves and the flexor muscles of the hands pass)
S: (n) root canal (the passage in the root of a tooth through which its nerve and blood vessels enter the pulp cavity)