Illustration of the circulatory system in which the heart pumps blood is critical to healthy organs, muscles and tissues, with blood delivering nutrients and oxygen to all cells in the body. This cardiovascular system pumps blood from the heart to the lungs to get oxygen. The heart sends the oxygenated blood through the arteries, shown in red, under pressure to the rest of the body. The main artery is the aorta (A) . The carotid arteries (C.A.) supply oxygenated blood to a large part of the brain that controls thought and speech etc. The jugular vein (J.V.) is along side C.A.The veins, in blue, carry deoxygenated blood from the body back to the heart where it can be sent to the lungs. Valves in the heart keep blood flowing in one direction. In the left or right cavities of the heart , the upper chamber is an auricle (eg L.A. or R.A.) , whilst the lower chamber is a ventricle (L.V. or R.V.)