the digestive system

• Trachea


  • Contains rings of cartilage to prevent it from collapsing when we inhale
• Air passage into the lungs

  1. Trachea

  2. Bronchi

  3. Bronchioles

  4. Alveoli
• Alveoli


  • Microscopic air sacs where gas exchange occurs
• Alveoli adaptations for gas exchange


  • Huge surface area
  • Very thin walls (short diffusion path)
  • Good blood supply
• Oxygen diffuses into the bloodstream


  Carbon dioxide diffuses out of the bloodstream
• Breathing

  Brings fresh oxygen into the alveoli and takes away carbon dioxide, increasing the concentration gradients and rate of diffusion
• Cardiovascular diseases


  Diseases of the heart and blood vessels
• Cardiovascular diseases


  • They are non-communicable, meaning they cannot be passed from person to person
• 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
• 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


  1. Donated heart or heart and lungs

  2. Shortage of donated hearts

  3. Patient must take drugs to prevent rejection
• Artificial heart


  • Temporary solution to allow damaged heart to rest or while waiting for transplant
  • Increases risk of blood clots, not a long-term solution
• Blood plasma


  The liquid part of the blood
• 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

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

  • Contain the oxygen-carrying molecule hemoglobin
  • Have no nucleus, allowing more space for hemoglobin
  • Have a biconcave disk shape for greater surface area
• Function of red blood cells


  Transport oxygen from lungs to body cells
• White blood cells


  • Part of the immune system, make antibodies
  • Contain a nucleus with DNA
• Platelets


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

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


  Donated blood must be the same blood type as patient, otherwise immune system will reject it
• Using blood products


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


  Carry very high pressure blood from the heart to the organs in the body
• 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


  Carry blood back to the heart
• 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, and this surge can be felt in the wrist as your pulse
• Once the blood has passed through the organs, it now makes its way back to the heart through the veins