Pumped by the heart, the blood carries oxygen and nutrients to tissues for growth and metabolism, and removes metabolic wastes. An exchange of gases occurs in an important circuit called the pulmonary circuit, within the alveoli of the lungs. The right side of the human heart receives deoxygenated blood from body tissues and pumps it to the lungs. The left side of the heart receives oxygenated blood from the lungs and pumps it to the tissues. An important measurable aspect of the circulatory system is blood pressure .
Blood pressure is increased throughout all the arteries when the ventricles of the heart contract.
This is directly dependent on the amount of blood pumped by the heart and the resistance to blood flow through the arterioles. A sphygmomanometre is a device that measures arteriole blood pressure, consisting of an inflatable cuff connected by rubber hoses to a hand pump and a pressure gauge graduated in millimetres of mercury. The cuff is wrapped around the upper arm and inflated to a pressure that will shut off the brachial artery. The examiner then listens for the sounds of Korotkoff. These sounds are divided into five phases and are characterized by differences in quality and loudness.