Circulatory System

• The heart is the same size as our fists.
• The heart is located between the lungs, behind the sternum.
• Semilunar valve separates the ventricles from the great vessels.
• Pericardium is the membrane that surrounds the heart and protects it from external forces.
• Septum is the dividing wall between the left and right sides of the heart.
• Blood flows through the heart in one direction only due to the presence of valves that prevent backward flow.
• Atrioventricular valves separate the atria from the ventricles.
• Valves are flaps of tissue that open and close with blood pressure changes.
• Valves are made up of flaps called cusps or leaflets.
• The semilunar valves separate the ventricles from the arteries.
• The AV valve on the right side of the heart is called the tricuspid valve, while the AV valve on the left side is called the bicuspid valve.
• The tricuspid valve separates the right atrium from the right ventricle.
• The bicuspid valve separates the left atrium from the left ventricle.
• The pulmonary trunk carries blood to the lungs.
• Blood flows from the body into the right atrium, then to the right ventricle, which pumps it to the lungs. Oxygenated blood returns to the left atrium, moves to the left ventricle, and is then pumped out to the body.
• The heart has four chambers — two atria (upper chambers) and two ventricles (lower chambers).
• The valves open and close in response to pressure changes in the heart chambers. When the ventricles contract (systole), the AV valves close to prevent backflow, and the semilunar valves open to allow blood to be pumped out. When the ventricles relax (diastole), the semilunar valves close to prevent backflow, and the AV valves open to allow the chambers to fill with blood.
• The right atrium receives oxygen poor blood from all over the body.
• The left atrium receives oxygen rich blood from the lungs.
• The right ventricle pumps deoxygenated blood towards the lungs.
• The left ventricle pumps oxygenated blood to the aorta.
• The bicuspid valve is also called the mitral valve.
• Blood vessels transport blood throughout the body.
• Arteries carry blood away from the heart.
• The elastic fibres of arteries allow the artery to stretch under pressure.
• The thick muscles of arteries can contract to push the blood along.
• Veins carry blood towards the heart.
• Capillaries link arteries with veins. They are also the tiniest blood vessels.
• The exchange of materials between the blood and the body can only occur through capillaries.
• The wall of a capillary is only one cell thick.
• A collection of capillaries is known as a capillary bed.
• Label

  A) artery

  B) vein

  C) body cell

  D) capillaries

  
• Blood is a connective tissue that looks like a plain red fluid.
• Label

  A) RBC

  B) WBC

  C) Platelets

  D) Plasma

  
• Red blood cells or erythrocytes contain hemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it.
• RBC is a biconcave disc that is round and flat without a nucleus and can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries.
• White blood cells are also called leukocytes because they lack hemoglobin and do not give blood its characteristic color.
• There are many different types of WBC and all contain a big nucleus.
• Macrophages eat and digest micro-organisms.
• Some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them. Other lymphocytes make antitoxins to break down poisons.