venation vs venous blood system

venation and venous blood system both are nouns.

Word	Noun	Adjective	Verb	Adverb
venation	Yes	No	No	No
venous blood system	Yes	No	No	No

As nouns, venation and venous blood system are synonyms defined as:

venation and venous blood system: (zoology) the system of venous blood vessels in an animal

venation (noun)	venous blood system (noun)
(zoology) the system of venous blood vessels in an animal	(zoology) the system of venous blood vessels in an animal
(botany) the arrangement of veins in a leaf