Bio

• Transport system


  Rapidly carries fluids containing nutrients and waste products to and from different parts of the body
• Components of circulatory systems

  • Circulatory fluid: a transport medium e.g. blood
  • Vascular system: tubes through which the transport medium can flow e.g. arteries, veins, capillaries
  • Pump: generates the force needed to circulate the transport medium around the body e.g. the heart

  
• Bulk transport


  A property of the transport system
• Small organisms have a small surface area to volume ratio and can use diffusion as it happens quick enough
• Larger organisms have a higher metabolic demand and diffusion would be too slow, so they have a transport system to transport materials together in bulk at a rate which does not depend on a concentration gradient, but on the force of the pump
• Atrio-ventricular valves


  Tricuspid and bicuspid valves between atrium and ventricle

  
• Heart


  • Muscular organ which pumps blood around the body
  • 4 chambers with muscular contractile walls: 2 on left and 2 on right
  • Atria receive blood, pump it to the ventricles, which pump it out of the heart
  • Ventricles contain more muscle because they must exert a larger force
  • Valves close during contraction to prevent blood from flowing back

  
• Right side of the heart

  • Deals with blood from body organs which is deoxygenated and rich in carbon dioxide
  • Delivers blood to the right atrium via the vena cava vein
  • Sends blood to the right ventricle which pumps it into the pulmonary artery, through which it is conducted to the lungs

  
• Left side of the heart

  • Deals with oxygenated blood from the lungs which arrives via the pulmonary vein
  • Blood enters the atrium, is transferred to the left ventricle, which contracts and forces the blood to the aorta
  • Walls of the left ventricle have more muscle tissue because it has to pump blood at a higher pressure to all the organs

  
• Action of the heart

  1. Atria collect blood from the body via veins

  2. Atria pump the blood to the ventricles

  3. Ventricles pump blood to the lungs via the pulmonary artery and the rest of the body via arteries

  4. Atria-ventricular and semi-lunar valves open and close to control the flow of blood and prevent the blood from flowing backwards

  
• Atrio-ventricular valves


  Between the atria and ventricles - prevent blood from flowing back to the atria when the ventricles contract

  
• Semi-lunar valves


  Between ventricles and the pulmonary artery and aorta, where the arteries leave the heart

  
• The heart itself is provided with blood via the coronary vessels

  
• Myogenic


  The walls of the heart are made of cardiac muscle which contracts of its own accord, without needing to be stimulated by nervous impulses from the brain
• Heart beat


  Can speed up or slow down under involuntary control, by nerves supplying the heart and hormones
• Arteries


  • Transport blood from heart to body parts
  • Thick and elastic to stretch but not rupture
  • Muscular to contract
  • High pressure

  
• Veins


  • Transport blood from body parts to heart
  • Thin and more expandable than arteries
  • Only slightly muscular
  • Low pressure, some assisted by muscular action of arms and legs during locomotion

  
• Capillaries


  • Link arteries and veins
  • One cell thick to allow diffusion
  • Not muscular
  • Very low pressure to allow time for exchange of materials
• Tissue fluid


  Medium for diffusion between tissue cells and blood in capillaries

  
• Blood composition


  • Plasma
  • Erythrocytes
  • Leucocytes
  • Platelets

  
• Plasma


  Straw-coloured liquid made of 90% water and 10% dissolved and suspended substances including proteins, nutrients, hormones, gases, salts and wastes. It transports substances and distributes heat.
• Erythrocytes


  Circular, biconcave flexible cells which lack a nucleus. Rich in haemoglobin to transport oxygen and carbon dioxide.
• Leucocytes


  Larger than rbc but fewer, have a nucleus sometimes large. Part of immune system- protect the body from foreign invaders.
• Platelets


  Irregularly shaped membrane-bound cellular fragments which lack a nucleus. Important for blood clotting.
• Blood cells are made in the bone marrow

  
• Health problems related to disorders of the transport system

  • Coronary heart disease
  • Heart pacemakers
  • Haemophilia
• Coronary heart disease


  Major blood vessels that supply the heart become damaged or diseased, decreasing blood flow and potentially causing a heart attack

  
• Irregular heartbeat


  A pacemaker is an implanted device to help manage irregular heartbeats like tachycardia and bradycardia
• Haemophilia


  A rare condition that affects the blood's ability to clot, causing prolonged bleeding

  
• There's no cure for haemophilia, but treatment involving genetically engineered clotting factor medicines are used to prevent and treat prolonged bleeding