Double Circulatory System

• Red Blood cells carry oxygen
• RBCs have a biconcave shape to increase the surface area for absorbing oxygen
• they don't have a nucleus increasing the surface area for oxygen
• RBCs contain a red pigment called haemoglobin. in the lungs it binds to oxygen and produces oxyhaemoglobin and in the body tissues it separates to produce haemoglobin and oxygen to release oxygen into cells
• White blood cells absorb invading pathegons in a process called phagocytosis.
• some WBCs produce antibodies to fight pathogens as well as antitoxins
• WBCs do have a nucleus
• platelets clot wounds to stop microorganisms getting in and blood pouring out
• a lack of platelets can lead to excessive bruising and bleeding
• Plasma Is a liquid that carries everything in the blood
• plasma carries RBCs, WBCs and platelets
• Plasma carries nutrients like amino acids and glucose to cells
• Plasma also carries Urea, proteins, hormones, antibodies, antitoxins and carbon dioxide
• Arteries carry blood away from the heart
• capillaries are involved in the exchange of substances between the blood and the tissues
• veins carry blood to the heart
• arteries carry blood under high pressure from the heart to the body so they have thick elasticated walls
• The lumen of an artery is small to maintain the high pressure of the blood
• the thick walls of arteries contain muscles to make them strong and contain elastic fibres so they can stretch and spring back
• Capillaries carry blood really close to body cells to exchange substances with them
• Capillaries have permeable walls to allow substances to diffuse in and out
• capillaries supply food and oxygen and take away waste like carbon dioxide
• the walls are usually one cell thick. This increases the rate of diffusion as the Path it has to travel has decreased
• veins take blood back to the heart
• vein walls carry low pressure blood so they have thinner walls and a large lumen
• veins also have valves
• rate of blood flow = volume of blood/number of minutes
• the heart has valves to prevent the backflow of blood
• Circulation of oxygenated blood:

  1. Oxygenated blood enters the Pulmonary vein flowing into the left atrium.
  2. The left atrium then contracts pumping the blood into the left ventricle.
  3. The Left ventricle then contracts pushing the blood through the valves and out the aorta to the body to oxygenate cells.
• Circulation of deoxygenated blood:

  1. Deoxygenated blood comes from the body to the heart and flows into the right atrium through the vena carva.
  2. the atrium contracts pushing the blood into the right ventricle
  3. the ventricle contracts pushing blood out the heart through the pulmonary artery to be oxygenated by the lungs
• your resting heart rate is controlled by a group of cells in the right atrium called the pacemaker. these cells produce a small electrical impulse that triggers the heart to beat