1. Which of the following structures is responsible for the exchange of gases in the lungs? A. Alveoli B. Bronchi C. Trachea D. Diaphragm Answer: A. Alveoli Rationale: Alveoli are the tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide occurs, which is essential for respiration. 2. The primary function of the circulatory system is to: A. Transport nutrients and oxygen to cells B. Remove waste products from the body C. Protect the body against disease D. All of the above Answer: D. All of the above Rationale: The circulatory system is responsible for transporting nutrients, oxygen, and hormones to cells, removing waste products, and aiding the immune system in protecting the body. 3. Osteoporosis is a condition characterized by: A. Increased bone density B. Decreased bone density C. High levels of calcium in bones D. Thickening of bone marrow Answer: B. Decreased bone density Rationale: Osteoporosis involves a reduction in bone density, leading to fragile bones that are more prone to fractures. 4. The sinoatrial node is important because it: A. Regulates blood pressure B. Is the site of gas exchange C. Sets the pace for the cardiac rhythm D. Filters blood impurities Answer: C. Sets the pace for the cardiac rhythm Rationale: The sinoatrial node is known as the heart's natural pacemaker, initiating the electrical impulses that set the rhythm for the