Systole is the rhythmic phase of the cardiac cycle.

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

How can an organ, such as the lungs, work for multiple body systems?

Where does the esophagus lead to in a frog?