We as humans are made up of many structures and systems. These structures and systems are vital to us and a healthy lifestyle. The circulatory system is just one important system out of the three main ones. The rat that I have dissected in class has almost identical structures to that of a human. The circulatory system is made up of the heart and a network of blood vessels. It is also known as the cardiovascular system. The main purpose of this system is to transport materials to and from all parts of the body. The three kinds of blood vessels important to this system are arteries, capillaries, and veins. With each heartbeat, blood is sent through our bodies carrying oxygen and nutrients. Our bodies actually have two circulatory systems; the Pulmonary Circulation and the Systematic Circulation. The Pulmonary Circulation is a short loop from the heart to the lungs and back. The Systematic Circulation sends blood from the heart to all other parts of our bodies. The heart is the key organ in the circulatory system. It acts as a pump for these blood vessels. The heart is divided into four chambers that are enclosed by thick, muscular walls. It is divided into four chambers that take oxygenated and deoxygenated blood in and out of the heart. The bottom of the heart has two chambers that are called the right and left ventricles. The ventricles are divided by a wall called the inter-ventricular septum. The upper part of the heart is made up of the right and left atria. The atrias receive blood entering the heart. A wall called the interatrial septum separates the atrias. The pumping of the heart