descent vs blood line

descent and blood line both are nouns.

Word	Noun	Adjective	Verb	Adverb
descent	Yes	No	No	No
blood line	Yes	No	No	No

As nouns, descent and blood line are synonyms defined as:

Other synonyms of descent include ancestry, blood, bloodline, line, line of descent, lineage, origin, parentage, pedigree, stemma, stock.

descent (noun)	blood line (noun)
the act of changing your location in a downward direction	the hereditary derivation of an individual
properties attributable to your ancestry
a movement downward
the hereditary derivation of an individual
a downward slope or bend
the kinship relation between an individual and the individual's progenitors