Chap 9

• Most animals use the circulatory system as the primary method to transport nutrients and gases through the body
• Circulatory system in fish

  • System of blood vessels with a pump and valves to ensure one-way flow of blood
  • Fish have a single circulatory system with a heart consisting of an Atrium and a ventricle
  • Blood passes through the heart only once to complete a full circuit through the body
  • Deoxygenated blood from the body capillaries moves through the two chambers of a fish's heart, the Atrium and the ventricle, and then reaches the Gill capillaries where oxygen is absorbed into the blood
  • Blood becomes oxygenated and moves from the Gill capillaries to the body capillaries completing one circuit
• Gill circulation in fish

  1. Heart pumps blood to the gills to be oxygenated

  2. Blood then continues through the rest of the body before arriving back at the atrium

  3. This is called systemic circulation
• Double circulation in mammals

  • Mammals have a double circulatory system with a heart consisting of four chambers
  • Blood passes through the heart twice for every one circuit of the body
  • Deoxygenated blood enters the right atrium via the vena cava, moves into the right ventricle, is pumped to the lungs to become oxygenated, then enters the left atrium via the pulmonary vein, and moves to the left ventricle before being pumped to the rest of the body
  • The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (pulmonary circulation), while the left side receives oxygenated blood from the lungs and pumps it to the body (systemic circulation)
  • Double circulation allows faster and more efficient delivery of oxygen and glucose through the blood due to maintaining higher blood pressure
• Mammals have a greater requirement for oxygen and glucose for respiration compared to fish
• Structures of the mammalian heart include the right atrium, vena cava, tricuspid valve, etc.
• Thicker muscle walls in the ventricles

  Needed to pump blood out of the heart at a higher pressure
• Aorta carries oxygenated blood away from the heart to the rest of the body
• Pulmonary artery carries deoxygenated blood away from the heart to the lungs to be oxygenated
• Septum separates the two sides of the heart to prevent the mixing of oxygenated and deoxygenated blood
• Heart contraction

  Heart muscles contract to push blood through valves from atria to ventricles and out of the heart
• Structures of the mammalian heart

  • Right atrium
  • Vena cava
  • Tricuspid valve
  • Right ventricle
  • Semilunar valve
  • Pulmonary artery
  • Septum
  • Left atrium
  • Pulmonary vein
  • Bicuspid valve
  • Left ventricle
  • Semilunar valve in the aorta
  • Aorta
• Double circulation

  Deoxygenated blood enters the right atrium through the vena cava, moves into the right ventricle through the atrioventricular valve (tricuspid valve), pumps out to the pulmonary artery via the semilunar valve, travels to the lungs, becomes oxygenated, returns to the heart via the pulmonary vein into the left atrium, moves into the left ventricle through the atrioventricular valve (bicuspid valve), pumps out to the aorta via the semilunar valve, and is carried away from the heart to the rest of the body
• Coronary arteries supply blood to the heart muscle
• Activity of the heart may be monitored by

  Using an ECG, measuring pulse rate, or listening to the sounds of valves closing using a stethoscope
• Effect of physical activity on heart rate

  Record pulse rate at rest for a minute, exercise, then record pulse rate every minute until it returns to the resting rate
• Coronary arteries supply blood to

  Heart muscles for respiration and function
• During exercise

  Heart rate increases and may take several minutes to return to normal
• Coronary heart disease caused by

  Buildup of cholesterol and other fatty substances within the coronary arteries
• Coronary heart disease


  • Caused by blocked coronary artery leading to blood and oxygen starvation in the heart muscles
• Reason for increased heart rate during exercise

  Muscle cells need more energy, oxygen, and glucose for respiration, waste products of respiration need to be removed faster, oxygen debt needs to be repaid
• Conclusion of part 1 of chapter 9 transport in animals
• Ways to reduce the risk of coronary heart disease

  Quit smoking, maintain a healthy diet with reduced animal fats, exercise regularly
• Thicker muscle walls in ventricles

  Needed to pump blood out of the heart at a higher pressure
• Left ventricle's thicker muscle wall

  Due to pumping blood at a higher pressure to the whole body
• Risk factors for coronary heart disease

  • Diet, lack of exercise, diabetes, obesity, stress, smoking, genetic predisposition, age, gender
• Ventricles

  • Have thicker muscle walls than the Atria since they pump blood out of the heart at a higher pressure
  • Left ventricle's muscle wall is thicker than the right ventricle's as it pumps blood at a higher pressure to the whole body
• Veins carry deoxygenated blood except for the pulmonary vein
• Capillaries


  • One cell thick walls
  • Very thin permeable walls
  • Narrow Lumen just wide enough for a red blood cell to pass through
  • No valves present
• Veins

  • Thin muscular walls
  • Little elastic fibers in walls
  • Large Lumen
  • Valves present to prevent backflow
• Fluid leaks out of the capillaries and bathes the surrounding cells, forming tissue fluid
• Blood flows slow in veins
• Capillaries supply all cells with their requirements and take away their waste products
• Blood flows fast in arteries
• Valves are present in veins unlike arteries
• Capillaries are the smallest of blood vessels that connect arteries and veins
• Arteries


  • Thick muscular walls to withstand high pressures
  • Elastic fibers in walls
  • Narrow Lumen to maintain high blood pressure
• Arteries do not have valves
• Capillaries carry both oxygenated and deoxygenated blood
• Blood flows slowly in capillaries at low pressure