Transport in human

• Circulatory system


  A system of tubes with a pump and valves to ensure one way flow of blood
• Functions of the circulatory system

  • To transport nutrients and oxygen to the cells
  • To remove waste and carbon dioxide from the cells
  • To provide for efficient gas exchange
• Blood flow through the heart

  1. Right side collects deoxygenated blood from the body and pumps it to the lungs

  2. Left side collects oxygenated blood from the lungs and pumps it to the body
• Double circulation


  Blood travels through the heart twice on one complete journey around the body: one circuit links the heart and lungs (low pressure circulation), the other circuit links the heart with the rest of the body (high pressure circulation)
• Importance of double circulation

  • Oxygenated blood is kept separate from deoxygenated blood
  • The blood pressure in the systemic circulation is kept higher than that in the pulmonary circulation
• Heart's function


  • Blood circulation: Blood in the right ventricle is pumped to the lungs, blood from the lungs flows into the left atrium and then into the left ventricle, blood in the left ventricle is pumped through the body
  • Muscular contraction: The heart is made of cardiac muscle which contracts and relaxes regularly
  • Working of the valves: Valves in the heart prevent blood from being pushed backwards up into the atria
• The heart's muscle is constantly active, so it needs its own blood supply, through the coronary artery, to provide it with oxygen and glucose
• How the heart pumps blood

  1. Blood in the right ventricle is pumped to the lungs

  2. Blood from the lungs flows back into the left atrium and then into the left ventricle

  3. Blood in the left ventricle is pumped through the body

  4. Blood returns to the heart where it enters the right atrium
• Blood passing through the chambers of the heart does not supply the heart muscle with oxygen or glucose. The heart muscles has its own blood supply - via the coronary arteries - to do this
• During exercise


  The heart rate increases to supply the muscles with more oxygen and glucose, allowing the muscles to respire aerobically and have sufficient energy to contract
• Regular exercise is important to keep the heart muscle in good tone, making the heart more efficient in maintaining blood pressure and reducing the risk of coronary heart disease and stroke
• Coronary arteries


  Supply the heart muscles with a constant supply of nutrients so that it can keep contracting and relaxing
• If a coronary artery gets blocked

  The cardiac muscles run short of oxygen, they can not respire, can not obtain energy to contract, and the heart stops beating. This is called a heart attack or cardiac arrest
• Main causes of coronary heart disease

  • Blockage of the coronary arteries
• Arteries


  Carry blood away from the heart, divide again and again, and eventually form capillaries
• Capillaries


  Gradually join up with one another to form veins, which carry blood towards the heart
• Transfer of materials between capillaries and tissue fluid

  1. As blood enters capillaries from arterioles, it slows down, allowing substances in the plasma, as well as O2 from red blood cells, to diffuse through the capillary wall into the surrounding tissues

  2. Liquid in the plasma also passes out, forming tissue fluid

  3. Waste products from the cells, e.g. CO2, diffuse back through the capillary walls into the plasma

  4. Some of the tissue fluid also passes back
• Diffusion is responsible for the transfer of materials between capillaries and tissue fluid