Chapter 12

• The four chambers of the heart create two separate pathways in which blood flows.
• Blood returns from the body and enters the heart through the superior and inferior vena cava.
• The blood enters the Right Atrium.
• When the atrium contracts the blood is forced out of the right atrium and into the Right Ventricle, while passing through the atrioventricular valve.
• The ventricles contract and blood flows from the right ventricle into the pulmonary artery, passing through the Semilunar Valve.
• The blood travels to the lungs where gases exchange takes place.
• The blood returns to the heart on the left side, traveling from the lungs to the heart in the pulmonary veins.
• The blood enters the Left Atrium.
• When the Atriums contract and the blood enters the Left Ventricle, while passing through the Left Atrioventricular valve.
• The blood in the ventricle is pumped out during a contraction.
• The blood passed through the Semilunar Valve and into the Aorta, where the blood travels to all parts of the body.
• The artery is highly elastic, allowing the arteries to expand as blood passes through under high pressure and return to its original diameter once the blood has passed on.
• The action of the artery forces blood to travel in one direction and maintains pressure on the movement of the blood.
• The vein has thinner walls and is less elastic than the artery, but it can expand its diameter wider than arteries and does not contract back to its original diameter right away, therefore not creating pressure on the movement of blood.
• To maintain one-way directional flow of blood in these vessels, there are valves which work against gravity.
• Capillaries are the smallest vessel in diameter (8 µm), so small that red blood cells can only pass through one at a time in single file order.
• There are more capillaries in the body than any other vessel.
• The Mammalian circulatory system is set up to maximize the delivery of oxygen to support the high energy demands, and the removal of metabolic wastes.
• Oxygen rich blood (oxygenated) and oxygen poor blood (deoxygenated) do not have the opportunity to mix.
• The circulatory system is divided into separate pathways, Pulmonary and Systemic circulation.
• Pulmonary Circulation: the path that blood follows from the heart to the lungs and back to the heart.
• Systemic Circulation: the path that blood follows from the heart to the body and back to the heart.
• Cardiac Circulation: the movement of blood though the heart tissues.
• The Pulmonary circulation starts when the deoxygenated blood leaves the Right Ventricle and enters the Pulmonary Arteries.
• The pulmonary arteries deliver blood to the right and left Lungs, where gas exchange takes place.
• The blood leaving the lungs is now oxygenated and heads back to the Heart passing through the Pulmonary Veins.
• The blood now enters the heart at the Left Atrium.
• The Systemic circulation starts when oxygenated blood leaves the Left Ventricle, passing into the Aorta.
• Here blood is transported to all the body cells, where gas exchange takes place.
• The blood returning to the Heart is deoxygenated.
• The blood passes into the Right Atrium via the Superior and Inferior Vena Cava.
• At any time 80 to 90 percent of your blood is found in the systemic system.
• Cardiac circulation is the movement of blood through the heart muscle tissue, via the Coronary Artery.
• The coronary arteries supply the heart muscle with the O2 and nutrients its cells need so they can carry out their metabolic activities.
• An adult human has about 5 litres of blood passing continuously through the vessels of their body.
• Blood is also known as connective tissue because it links all cells and organs of the body together, yet it is a fluid.
• Blood can be sub-divided into two distinct parts; the fluid portion called plasma and the solid portion made up of blood cells and platelets.
• Plasma is a clear, yellowish fluid composed of 92% water, 7% proteins (albumin, globulins and fibrinogen, 1% organic (glucose, fatty acids and vitamins), and inorganic substances (Na+, K+, Cl_ and HCO3_).
• The blood also contains dissolved O2 and CO2.
• Plasma also transports to the kidneys for disposal.