1. Rank the following from highest oxygen content to lowest: the air inside the alveoli, a working arm muscle, arteries to the arm, capillaries that supply the arm muscle. 2. In a developing embryo,...

1. Rank the following from highest oxygen content to lowest: the air inside the alveoli, a working arm muscle, arteries to the arm, capillaries that supply the arm muscle.

2. In a developing embryo, the heart begins to beat long before developing nerves reach it. How is the embryonic heart able to beat without nervous system control?