spinal canal vs epithelial duct

spinal canal and epithelial duct both are nouns.

Word	Noun	Adjective	Verb	Adverb
spinal canal	Yes	No	No	No
epithelial duct	Yes	No	No	No

As nouns, epithelial duct is a hypernym of spinal canal; that is, epithelial duct is a word with a broader meaning than spinal canal:

spinal canal: the canal in successive vertebrae through which the spinal cord passes
epithelial duct: a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance

Other hypernyms of spinal canal include canal, channel, duct.

spinal canal (noun)	epithelial duct (noun)
the canal in successive vertebrae through which the spinal cord passes	a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance