The Circulatory System

• Blood


  Blood is made up of red blood cells (about 45%), white blood cells (less than 1%), plasma (about 55% ) and platelets. The red and white blood cells as well as platelets are suspended in the plasma.
• Red Blood Cells


  Also called Erythrocytes, these cells transport oxygen around the body with their pigment named haemoglobin that can carry 4 oxygen molecules each. This makes the cells red, as well as changing the intensity of the red when there is more oxygen being transported. Their small size allows them to fit in capillaries. They are biconcave, allowing for a larger surface area thus more oxygen transported.
• Plasma


  About 55% of blood, it has nutrients and wastes dissolved in it and has Red Blood Cells, White Blood Cells and Platelets suspended in it. It is straw/yellow coloured.
• Artery


  Thick-walled vessel that transports blood away from the heart. They are high-pressure and without valves and therefore elastic so it can return to its original shape after blood is pumped. Small Lumen. No valves
• Capillary


  Tiny vessels with 1-cell thick walls that allow them to deliver nutrients to and remove wastes from cells around them via diffusion with chemicals such as oxygen and carbon dioxide. The are low pressure, have a very small lumen and no valves.
• Vein


  Transports blood to the heart under low pressure therefore it has thin walls. Valves are present to prevent back-flow of blood. Low elasticity.
• Circulatory System


  The circulatory system is responsible for transporting oxygen and nutrients to your body’s cells, and wastes such as carbon dioxide away from them. It includes the heart, blood vessels and blood within.
• Blood Vessels


  Pipes which carry blood around the body such as Arteries, Veins and Capillaries.
• An average adult has 5 litres of blood.
• Red Blood Cells


  Makes up 45% of blood and is also called Erythrocytes. Red due to haemoglobin, which also allows them to carry oxygen. No nucleus or organelles. Biconvave shape. Red intensity changes based on how much oxygen is being carried.
• White Blood Cells


  Larger than red blood cells but in fewer numbers in red blood cells and contain nuclei. They help fight infections and diseases, some using antibodies while others engulf foreign matter. They are colorless, and the total amount increases when you are ill.
• Plasma


  About 55% of the blood, it has nutrients and wastes dissolved in it as it transports dissolved material to and from cells. It has the other components of the blood suspended in it and is straw coloured.
• Platelets


  Less than 1% of the blood, they are very small and they clot blood and repair damaged blood vessels.
• Aorta


  Main artery out of the heart carrying oxygen-rich blood and goes down most of the body.
• Pulmonary Artery


  The only artery that holds deoxygenated blood and takes it to the lungs.
• Inferior Vena Cava


  The main vein which all lower-body veins connect to that brings deoxygenated blood to the heart.
• Superior Vena Cava


  The main vein which all upper-body veins connect to that brings deoxygenated blood to the heart.
• Pulmonary Vein


  The only vein that holds oxygenated blood. It takes this blood from the lungs to the heart.
• Right Atrium


  Receives deoxygenated blood from the Vena Cava and is low-pressure.
• Right Ventricle


  The pump which pumps deoxygenated blood to the pulmonary artery, eventually leading to the lungs.
• Left Atrium


  Receives oxygenated blood from the pulmonary vein to be sucked into the left ventricle.
• Left Ventricle


  The only high-pressure chamber of the heart, pumping oxygenated blood away from the heart into the aorta. It has thick walls due to its high pressure.
• Papillary Muscles


  Attaches to the Tricuspid Valve and Mitral Valve via Chordae Tendineae to open and shut the valve as well as preventing them from collapsing or letting blood backwards through the system.
• Where does the lub dub sound come from?


  The lub is from the valves separating the atria and ventricles shutting. The dub is from the closing of the valves in the blood vessels to and from the heart.
• Pathway of blood through the circulatory system

  Vena Cavas --> Right Atrium --> Right ventricle --> Pulmonary artery --> lungs --> Pulmonary Vein --> left atrium --> left ventricle --> body --> vena cavas