Blood does not leave the vessels in animals with a ____________. 

Sperm form in the __________ and are stored in the _____________.

Which of the following is true of the large intestine?

The spleen filters _______________ of pathogens.

The human heart pumps blood through 2 circuits: ______________.

________ are hypersensitivities whereby the immune system overreacts to environmental _________. 

Explain the difference between natural active immunity and natural passive immunity. 

Which part of the male reproductive system the target of a vasectomy?

_____________ is the basis of most home pregnancy tests. 

True or False: The lymph nodes filter lymphatic fluid.