What two systems work together to perfuse the body's tissues?

• A. Cardiovascular and Respiratory
• B. Nervous and Endocrine
• C. Digestive and Urinary
• D. Integumentary and Lymphatic

Answer: (A)

Tissue perfusion depends on two systems working together: the circulatory system moves blood through the body, delivering oxygen and nutrients, while the respiratory system oxygenates that blood in the lungs and removes carbon dioxide. Blood leaving the lungs is rich in oxygen and travels to tissues via the heart and vessels; at the capillaries, oxygen diffuses into cells and CO2 diffuses back into the blood. The heart’s pumping creates the pressure needed to push blood through the system, and the lungs continuously refresh that blood by gas exchange. Without the respiratory system, blood wouldn’t be properly oxygenated; without the circulatory system, that oxygenated blood wouldn’t reach tissues.