The classification system is always evolving as scientists continuously question the organization and placement of organisms.

Thinking about a negative feedback system, the ______ is the condition being measured and the ______ is the target of the actions of the control center.

The ____ has walls made up of C-shaped cartilages with inner walls made of smooth muscle and connective tissue which allow it to be flexible and rigid at the same time. 

The _____ is the spoon-shaped flap of cartilage that closes the opening of the larynx during swallowing.

The _____ are paired organs found inside the pleural cavities. 

________ ________ is gas exchanged between blood in capillaries and the interstitial fluid. 

The ______. _______ is where gas exchange occurs and contains the lungs and all of their components. 

How many lymphatic ducts are located in the body that drain lymph into veins near the heart?

_____ ______ are small organs that filter lymph and are fully of white blood cells which destroy bacteria and foreign particles. 

The top chambers of the heart that receive blood coming into the heart are called _____.