Part 1: The cardiovascular system (the heart and blood vessels) is the most vitally important organ system in the body. Your heart pumps blood, and your blood vessels channel and deliver nutrient-rich oxygenated blood throughout your body.
Part 2: The cardiovascular system (the heart and blood vessels) is the most vitally important organ system in the body. Your heart pumps blood, and your blood vessels channel and deliver nutrient-rich oxygenated blood throughout your body.
Part 1: The human respiratory system—of which the lungs are the largest component—is the most high-tech air purification and conditioning system on earth.
Part 2: The human respiratory system—of which the lungs are the largest component—is the most high-tech air purification and conditioning system on earth.