Introduction The circulatory (or cardiovascular) system is the transport system of the body and has four major functions: 1. Transportation of O2 and CO2 2. Transportation of wastes and nutrients 3. Transportation of hormones 4. Maintain body temperature. Structure of the Circulatory System A circulatory system consists of three parts: 1. A fluid in which materials are transported (i.e. blood) 2. A system of vessels to transport the fluid all over the body (i.e. arteries and veins) 3. A pump (i.e. heart) Interesting Facts No cell in your body is more than two cells away from a blood vessel. There are 96 000 km of blood vessels in your body to sustain your 100 trillion cells. Your heart beats around 72 times a minute and in your lifetime it will pump enough blood to fill two ocean tankers! Two Systems in One The left and right side of your heart do different functions. The right side of your heart pumps blood to the lungs to exchange CO2 for O2 in the pulmonary circuit. The left side of your heart pumps oxygen rich blood around your body in the systemic circuit. Blood moving through the heart is the cardiac circuit. Lungs Heart Structure The wall separating the left and right sides of your heart is known as the septum. Each side has a thin walled atrium to collect blood above a more muscular ventricle that pumps blood. Between the different regions of the heart are valves to ensure blood only flows in one direction. Heart Sounds The heart beat is actually controlled within the heart itself by two bundles of nerves. The sinoatrial (SA) node acts as a pacemaker causing the atria to contract while the atrioventricular (AV) node ensures the ventricles contract a moment later. Lub-dub The sound we hear is caused by the closing of the heart valves. The “lub” is from the shutting of the valves between the atria and ventricles when blood is moved from the top to the bottom of the heart. The “dub” is the closing of the valves between the ventricles and the arteries that leave the heart. Blood Vessels Arteries carry blood away from the heart and have thicker walls to withstand the greater pressure of blood. Veins take blood back to the heart and have valves to ensure one way blood flow. Capillaries are the junction of arteries and veins where gases and nutrients are exchanged with body cells. Artery (from heart) Vein (to heart) Tracing the Path Blood Takes around the Body Homework 1) What are the four functions of a circulatory system? 2) What are the three main parts to a circulatory system? 3) What are two differences between an Atrium and a Ventricle? 4) Using three different points of criteria, compare arteries, veins and capillaries.