The circulatory system is made up of a group of organs that move blood throughout the body and is responsible for the flow of nutrients, oxygen, and other gases to and from all cells. It is also known as the body's transportation system. The system contains three essential components that make up the circulatory system: the heart, blood vessels, and blood. These elements are vital to the body for survival. It includes the pulmonary and systemic circulatory cycle. Furthermore, it contains these three independent systems working together; the heart (cardiovascular), the lungs (pulmonary), the arteries, veins, coronary and portal vessels (systemic). There are two primary circulatory circuits called the pulmonary circuit and the systemic circulatory circuit. The pulmonaryThe blood that is transported is very enriched with oxygen after leaving the lungs and proceeds to the tissues of the body. The farther the arteries move from the heart, they become smaller and narrower and are eventually called arterioles. Arterioles and arteries have almost the same structure and function. Arterioles have strong, thick muscular walls and a rather small passage for blood to pass in and out. Furthermore, they are the most highly regulated blood vessels in the blood and contain blood at the top. Each of these parts has a specific job so that the system can function properly. The primary function of the circulatory system is a fundamental circuit that begins and ends in the heart. Specifically, the system begins in the right atrium, the upper right chamber of the heart. As blood flows here, it continues through the other three chambers of the heart. Next, it goes directly to the lungs to remove any carbon dioxide and pick up oxygen, eventually ending up in the lower left chamber called the left.