Question

fill in the blank question
a system in which blood flows through two consecutive capillary networks before returning to the heart is called a(n) □ system.

Explanation:

In the context of the circulatory system in biology (a subfield of Natural Science), a portal system is defined as one where blood passes through two consecutive capillary networks before returning to the heart. For example, the hepatic portal system (blood from digestive organs goes to liver capillaries first, then to heart - related circulation) or the hypophyseal portal system (in the endocrine system). So the term that fits is "portal".

Answer:

portal