pericardium vs serous membrane

pericardium and serous membrane both are nouns.

Word	Noun	Adjective	Verb	Adverb
pericardium	Yes	No	No	No
serous membrane	Yes	No	No	No

As nouns, serous membrane is a hypernym of pericardium; that is, serous membrane is a word with a broader meaning than pericardium:

pericardium: a serous membrane with two layers that surrounds the heart
serous membrane: a thin membrane lining the closed cavities of the body; has two layers with a space between that is filled with serous fluid

Other hypernyms of pericardium include serosa.

pericardium (noun)	serous membrane (noun)
a serous membrane with two layers that surrounds the heart	a thin membrane lining the closed cavities of the body; has two layers with a space between that is filled with serous fluid