Bio

• Double circulation system


  When blood passes through the heart twice on one complete circuit of the body
• Pulmonary circulation


  Moves blood between the heart and the lungs. The oxygenated blood then flows back to the heart.
• Systemic circulation


  Moves blood between the heart and the rest of the body. It sends oxygenated blood out to cells and returns deoxygenated blood to the heart.
• Single circulation


  When blood passes through the heart only once on a complete circuit
• Single circulation of a fish

  1. Deoxygenated blood comes to the heart and pumped to the gills through arteries

  2. Gaseous exchange happens within the gills

  3. Absorbs oxygen and releases carbon dioxide

  4. Flows from the gills to organs and tissues in the rest of the body and back to the heart
• In single circulation blood pressure is limited by tiny capillaries in the gills, so low pressure blood travels much more slowly to a fish's body organs
• Double circulation system


  The blood is pumped from the heart to the gas exchange organ, back to the heart and then the rest of the body
• Double circulation of a mammal

  1. Right side of heart receives deoxygenated blood from body and pumps it to lungs

  2. Blood gains oxygen but loses pressure in lungs

  3. Left side of heart receives oxygenated blood and sends it through aorta to rest of body with high pressure
• Advantages of double circulation

  • Heart pumps blood twice, so higher pressure can be maintained
  • Blood travels more quickly to organs
  • Delivers oxygen quickly and effectively to metabolically active tissues
  • Separates oxygenated and deoxygenated blood
  • Maintains different pressure to lungs and rest of body
• Heart


  Muscular organ made up of special cardiac muscles, present in the center of the thorax between two lungs, covered with a thin membrane called pericardium, separated into two halves (left and right) by septum, upper two chambers are atria and lower two chambers are ventricles, ventricles supported by thick muscles, left ventricle has thicker muscle than right ventricle
• Tricuspid valve

  Separates right atrium and right ventricle
• Bicuspid valve


  Separates left atrium and left ventricle
• Semi-lunar valve


  In pulmonary artery and aorta, prevents backflow of blood
• Heart beats about 60-75 times per minute in the average adult at rest
• Ventricles have thicker walls than atria


  Ventricles pump blood out of the heart and all around the body, so need thicker, more muscular walls
• Left ventricle has thicker wall than right ventricle


  Left ventricle pumps blood to whole body through aorta with high blood pressure, right ventricle only pumps to lungs which are close to heart
• Septum


  Divides left and right side of heart, important because blood in right side is deoxygenated and left side is oxygenated
• Systole


  When the heart muscle contracts, the heart becomes smaller, squeezing blood out
• Diastole


  When the heart muscle relaxes, the heart becomes larger, allowing blood to flow into the atria and ventricles
• Cardiac cycle


  1. Atrial diastole

  2. Atrial systole

  3. Ventricular systole

  4. Ventricular diastole
• Physical activity


  Increases heart beat rate to deliver more oxygen to muscles
• ECG


  Records the electrical activity in the heart, can be used to diagnose cardiovascular diseases
• Stethoscope


  Used to hear the sounds of the heart valves closing, each 'lub-dup' represents one heartbeat
• Pulse rate


  Same as heart rate, can be felt where an artery is near the skin surface
• Coronary arteries


  Blood vessels that supply blood, food and oxygen to the heart muscles
• Coronary heart disease (CHD)

  Coronary arteries become blocked by buildup of fatty substances including cholesterol, reducing blood flow and causing heart attacks
• Risk factors for coronary heart disease

  • Heredity
  • Age
  • High blood cholesterol
  • High blood pressure
  • Smoking
  • Diabetes
  • Obesity
  • Lack of exercise
  • Stress
• Coronary arteries


  Blood vessels that carry blood with food and oxygen to the heart muscles
• Figure 9.10 shows a normal ECG trace. The points labelled P, Q, R, S and T represent different stages of a heart beat.
• Coronary heart disease (CHD)


  The coronary arteries are blocked by buildup of fatty substances including cholesterol, making the lumen of the artery narrower. This increases the blood pressure and makes the artery wall much stiffer. Blood clots can form, and if one breaks away it can get stuck in a smaller blood vessel and stop the blood flow, causing a heart attack.
• Risk factors of coronary heart disease

  • Heredity
  • Age
  • Gender
  • Smoking
  • Stress
  • Diet
  • Excessive alcohol consumption
  • Lack of exercise
  • Being overweight
• Prevention of CHD


  1. Avoid smoking

  2. Take balanced diet

  3. Maintain ideal body weight

  4. Avoid diet rich in animal fat, high salt and excess food

  5. Avoid drinking alcohol

  6. Take regular exercise

  7. Get 6-7 hours sleep at night

  8. Lead a life free from emotional stress and anxiety
• Blood vessels


  • Aorta (carries oxygenated blood to all organs except lungs)
  • Pulmonary artery (carries deoxygenated blood from right ventricle to lungs)
  • Pulmonary vein (carries oxygenated blood from lungs to left atrium)
  • Vena cava (superior and inferior, bring deoxygenated blood to right atrium)
  • Renal artery (carries oxygenated blood to kidneys)
  • Renal vein (returns deoxygenated blood from kidneys)
  • Femoral artery (delivers oxygenated blood to leg and pelvic region)
  • Femoral vein (transports blood to inferior vena cava)
• During exercise, the rate of respiration becomes faster


  Produces more carbon dioxide, which dissolves in blood plasma reducing its pH. This is sensed by receptors in the brain, which increases the frequency of nerve impulses sent to the pacemaker.
• Pacemaker


  A patch of muscle in the right atrium that receives two sets of nerves from the brain - the accelerator nerve increases the heart rate and the decelerator nerve decreases the heart rate. The pacemaker adjusts the heart beat rate to meet the body's needs at rest, exercise and excitement.
• Functions of main blood vessels

  • Aorta (carries oxygenated blood to all organs except lungs)
  • Pulmonary artery (carries deoxygenated blood from right ventricle to lungs)
  • Pulmonary vein (carries oxygenated blood from lungs to left atrium)
  • Vena cava (superior and inferior, bring deoxygenated blood to right atrium)
  • Renal artery (carries oxygenated blood to kidneys)
  • Renal vein (returns deoxygenated blood from kidneys)
  • Femoral artery (delivers oxygenated blood to leg and pelvic region)
  • Femoral vein (transports blood to inferior vena cava)
• Action of atrioventricular valves during ventricular systole

  The valves are pushed closed by the high pressure of the blood in the ventricles, preventing blood from flowing back into the atria.
• Blood returns to the heart in the femoral vein against the pull of gravity


  Movement of legs causes contraction of muscles in the legs, pushing the blood forward. The femoral vein has valves to prevent backflow. The negative pressure in the heart and chest also helps blood return to the heart against gravity.
• Arteries


  • Take blood from the heart to the capillaries, usually contain oxygenated blood, have thick walls to withstand high blood pressure, contain muscular and elastic tissue for vasoconstriction/vasodilation and to maintain blood pressure, have folded endothelium and small lumen to allow larger blood flow, have fibrous tissue to maintain shape and prevent bursting, pulsing flow can be felt where they pass over bone near the skin.
• Veins


  • Have thin walls mainly of fibrous tissue, carry blood at low pressure towards the heart, have valves to prevent backflow, have few elastic fibers so flow is not pulsing, have large lumen to reduce resistance.