Transport in Animals

• Circulatory system

  The main transport system in animals, made up of blood vessels such as arteries, veins and capillaries in which blood travels around the body, carrying nutrients and waste products
• Fish circulatory system


  • Single circulatory system - heart has two chambers, blood passes through it only once on its circuit around the body, oxygen absorbed as blood passes the gills, no lungs
• Mammalian circulatory system


  • Double circulatory system - blood passes through the heart twice each circuit of the body, heart has four chambers to keep oxygenated and deoxygenated blood separate, greater need for oxygen for warmth as they are warm-blooded, more efficient at supplying oxygen and maintaining high blood pressure
• Heart function


  1. Deoxygenated blood enters right atrium

  2. Right atrium contracts, blood moves through tricuspid valve to right ventricle

  3. Right ventricle contracts, blood exits through semilunar valve to lungs via pulmonary artery

  4. Blood becomes oxygenated in lungs, returns to left atrium via pulmonary vein

  5. Left atrium contracts, blood moves through bicuspid valve to left ventricle

  6. Left ventricle contracts, oxygenated blood exits through semilunar valve to aorta and around body
• Heart structure


  • Left ventricle wall is thicker than right to pump blood at high pressure around body
  • Walls of both ventricles thicker than atria
  • Septum separates oxygenated and deoxygenated blood
• Valves


  Present in heart and veins to prevent backflow of blood, bicuspid and tricuspid valves are atrioventricular valves that prevent backflow between ventricles and atria, not present in arteries as pressure is high enough that backflow does not occur
• Deoxygenated blood travels in veins to the heart, oxygenated blood travels in arteries away from the heart, except for pulmonary artery and pulmonary vein
• Heart monitoring


  1. Electrocardiogram (ECG) records electrical signals causing heart contractions

  2. Pulse rate and valve activity can also be monitored
• Physical activity


  Increases short-term heart rate to deliver more oxygen to respiring muscles
• Diet and fitness


  Influence long-term heart rate, healthy diet and exercise result in lower resting heart rate, unhealthy diet high in salt and caffeine raises heart rate
• Coronary heart disease


  Caused by buildup of cholesterol in coronary artery, narrowing the artery and limiting blood flow to the heart
• Factors affecting coronary heart disease

  Diet high in saturated fat increases risk, regular exercise decreases risk by lowering blood pressure, other risk factors include stress, smoking, genetics, age and gender
• Treatments for coronary heart disease


  1. Drug treatment - aspirin to reduce risk by thinning blood and reducing platelet clumping

  2. Surgical treatments - stent to keep artery open, angioplasty to widen artery, coronary bypass to divert blood flow around damaged artery
• Arteries


  • Carry oxygenated blood at high pressure, have thick elastic and muscle layers to maintain pressure without bursting and control blood flow, branch into arterioles which enter tissues and become capillaries
• Veins


  • Carry blood at low pressure back to heart, have thin elastic and muscle layers, contain valves to prevent backflow, form from venules which are groups of capillaries
• Capillaries


  • Thin blood vessels adapted for efficient exchange of substances with tissues, have large surface area, narrow diameter and slow blood flow to decrease diffusion distance
• Shunt vessels


  • Connect arteries to veins without blood passing through capillaries, can dilate and constrict to control blood flow and reduce heat loss in cold conditions
• Tissue fluid


  Formed from capillary exchange, bathes cells and allows diffusion of nutrients and waste, most reabsorbed but larger molecules enter lymph system
• Lymphatic system


  Made up of lymph vessels and lymph nodes, carries lymph fluid containing large molecules that cannot re-enter capillaries, lymph nodes filter lymph fluid and protect against infection
• Blood components


  • Red blood cells containing haemoglobin to transport oxygen
  • White blood cells including lymphocytes that produce antibodies and phagocytes that engulf pathogens
  • Platelets involved in blood clotting
  • Plasma containing dissolved substances
• Phagocytosis


  1. Phagocyte recognizes and attaches to pathogen

  2. Phagocyte membrane envelopes and traps pathogen

  3. Phagocyte releases enzymes to break down and kill pathogen
• Blood clotting

  1. Platelets stick to broken vessel wall and clump together

  2. Fibrinogen converted to fibrin which forms mesh to block cut

  3. More platelets stick to fibrin mesh, forming scab to prevent blood loss and pathogen entry while vessel heals