Question

The human cardiovascular system is considered closed because __________.

Answer 1

Answer:

There are no holes for blood to enter or leave the system

Answer 2

Vertebrates, and a few invertebrates, have a closed circulatory system. Closed circulatory systems have the blood closed at all times within vessels of different size and wall thickness. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities.