tissue layer vs retina

tissue layer and retina both are nouns.

Word	Noun	Adjective	Verb	Adverb
tissue layer	Yes	No	No	No
retina	Yes	No	No	No

As nouns, retina is a hyponym of tissue layer; that is, retina is a word with a more specific, narrower meaning than tissue layer:

tissue layer: a pliable sheet of tissue that covers or lines or connects the organs or cells of animals or plants
retina: the innermost light-sensitive membrane covering the back wall of the eyeball; it is continuous with the optic nerve

tissue layer (noun)	retina (noun)
a pliable sheet of tissue that covers or lines or connects the organs or cells of animals or plants	the innermost light-sensitive membrane covering the back wall of the eyeball; it is continuous with the optic nerve