______________ system comprises of blood, blood vessels and heart.
Assertion (A): A complex of blood vessels beginning and ending in capillaries through which blood circulates before returning to the heart is called a portal system.
Reason (R): All mammals have a hepatic portal system.
Statement 1: A complex of blood vessels beginning and ending in capillaries through which blood circulates before returning to the heart is called a portal system.
Statement 2: All mammals have a hepatic portal system.
What do you call a circulatory system where blood flows through tubes called blood vessels?