The principal warriors in specific immune responses are the trillion or so _______ stationed strategically in the lymph tissue.

Which of the following veins carries blood rich in oxygen?

Which of the following best explains the proximate cause of bird migration?

_______ occurs as the volume of interstitial fluid increases.

_______ defense mechanisms include barriers that prevent pathogens from entering the body.

_______ often evade the immune system and multiply in an uncontrolled way.

Antibodies of the IgG and IgM groups activate _______.

The sequence of blood flow through the pulmonary circulation is _______.

Important function(s) of the lymphatic system is/are _______.

In _______, a cell flows around a bacterium and engulfs it.