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"
a continuous tube formed by a row of elongated cells lacking intervening end walls
something that provides access (to get in or get out); "they waited at the entrance to the garden"; "beggars waited just outside the entryway to the cathedral"