The circulatory and respiratory systems work together to transport oxygen, nutrients, and waste throughout the body. The circulatory system includes the heart, blood vessels, and blood. The heart pumps blood through a double circulatory pathway. Blood is composed of red blood cells, which carry oxygen, and white blood cells, which help fight infection. The respiratory system includes the nose, throat, lungs, and diaphragm. It takes in oxygen and releases carbon dioxide through breathing. Disorders of these systems can impair circulation or respiration and cause issues like heart disease or stroke.