BIOLOGY UNIT 2 BLOOD ETC

• Villi in Small Intestine

  • Very long (around 5 meters in humans)
  • Covered with millions of villi
  • Villi have micro villi that further increase surface area
  • Good blood supply to remove products of digestion
  • Thin membrane - short diffusion path
• Circulatory system in fish

  Deoxygenated blood is pumped from the heart to the gills where it collects oxygen and becomes oxygenated, the oxygenated blood then passes straight from the gills to the organs where the oxygen diffuses out of the blood and into the body cells, the blood now returns to the heart
• Problem with single circulatory system in fish

  The blood loses a lot of pressure as it passes through the gills before reaching the organs, this means the blood travels to the organs relatively slowly so it cannot deliver a great deal of oxygen
• Circulatory system in humans

  Deoxygenated blood is pumped from the heart to the lungs where it collects oxygen, this oxygenated blood then returns to the heart, the heart now pumps the oxygenated blood to the organs where the blood transfers its oxygen to the body cells, the blood now returns back to the heart
• Benefit of double circulatory system in humans

  Because the blood passes through the heart twice, it can travel rapidly to the body cells delivering the oxygen that the cells need
• Heart


  • An organ consisting mainly of muscle tissue
  • The job of the heart is to pump blood around the body
• Heart chambers

  4 chambers - left atrium, right atrium, left ventricle, right ventricle
• Valves


  Separate the atria from the ventricles
• Pattern of blood flow through the heart

  1. Blood enters the left and right atria

  2. Atria contract, forcing blood into the ventricles

  3. Ventricles contract, forcing blood out of the heart

  4. Valves prevent backflow into the atria
• Left ventricle


  • Has a thicker muscular wall than the right ventricle, as it pumps blood around the entire body and needs to provide greater force
• Coronary arteries


  Branch out of the aorta and spread into the heart muscle, their purpose is to supply oxygen to the muscle cells of the heart
• Pacemaker


  A group of cells found in the right atrium that control the natural resting heart rate
• Artificial pacemaker


  A small electrical device implanted by doctors to correct irregularities in the heart rate when the natural pacemaker stops working correctly
• Arteries


  • Have very thick muscular walls to withstand the very high pressure of the blood
  • Contain elastic fibers that stretch when the surge of blood passes through and then recoil in between the surges to keep the blood moving
• Capillaries


  Where substances such as glucose and oxygen diffuse from the blood to the cells, and carbon dioxide diffuses from the cells back to the blood
• Capillaries


  • Have very thin walls so the diffusion pathway is very short, allowing substances to diffuse rapidly between the blood and the body cells
• Veins


  • Have thin walls because the blood pressure is low
  • Contain valves that stop blood flow backwards when the blood is flowing in the correct direction
• Blood travels through the arteries and surges every time the heart beats, which can be felt as a pulse in the wrist
• Functions of blood plasma

  1. Transports dissolved substances around the body

  2. Transports soluble digestion products from small intestine to other organs

  3. Transports carbon dioxide from body cells to lungs to be breathed out

  4. Transports waste product urea from liver to kidneys to be excreted
• Red blood cells

  • Transport oxygen from lungs to body cells
  • Contain the oxygen-carrying molecule hemoglobin
  • Have no nucleus, allowing more space for hemoglobin
  • Have a biconcave disk shape, giving greater surface area for oxygen diffusion
• White blood cells


  Part of the immune system, make antibodies
• Platelets


  Tiny fragments of cells that help the blood to clot
• Uses of donated blood

  • Replace blood loss during injury
  • Platelets extracted to help in clotting
  • Proteins extracted, e.g. antibodies
• Blood transfusion


  Donated blood must be the same blood type as the patient, otherwise the body's immune system will reject it and the patient could die
• Coronary heart disease

  1. Layers of fatty material build up inside the coronary arteries

  2. Coronary arteries narrow

  3. Reduces blood flow and oxygen to the heart muscle

  4. Can result in a heart attack
• Using blood products

  Risk of transmitting infections
• In the UK, blood is screened for infection, so the risk is extremely low
• Statins


  Drugs which reduce the level of cholesterol in the blood, slowing down the buildup of fatty materials in the arteries
• Statins


  • Effective at reducing the risk of coronary heart disease
  • Can cause unwanted side effects like liver problems
• Stent insertion

  1. Stent is a tube inserted into the coronary artery to keep it open

  2. Allows normal blood flow but does not treat underlying causes
• Heart valve issues

  Valves do not fully open or are leaky, causing the heart to work harder
• Mechanical heart valves


  Made of metal, can last a lifetime but increase risk of blood clots
• Biological heart valves


  From animals, do not last as long and may need replacement, but no need for anti-clotting drugs
• Heart failure


  Heart cannot pump enough blood around the body
• Heart transplant


  Donated heart or heart and lungs, but limited availability and risk of rejection
• Artificial heart


  Temporary solution, increases risk of blood clotting, not a long-term treatment for heart failure
• Vena Cava


  Carries deoxygenated blood from the body back to heart
• Pulmonary Vein


  It transports oxygenated blood from the lungs to the heart
• Aorta


  It carries oxygenated blood from the heart to the body