Human circulation

• The Heart


  • Cone shaped, situated between the two lungs, size of a man's closed fist
• Pericardium/pericardial membrane


  Tough sac, double walled (with visceral and parietal layers), secretes pericardial fluid to reduce friction between heart wall and surrounding tissues
• Chambers of the heart

  • Right atrium
  • Right ventricle
  • Left atrium
  • Left ventricle
• Atria

  • Two chambers left and right
  • Located at the base of the heart
  • Receives blood from the body
  • With thin muscular walls for pumping blood into the ventricles
• Ventricles


  • Compose of two chambers left and right
  • Located at the apex of the heart
  • With thick muscular walls
• Heart Valves


  • Flaps of tissue in the heart and veins
  • Prevent the backflow of blood
• Types of Heart Valves

  • Atrioventricular valves (tricuspid valve, bicuspid/mitral valve)
  • Semilunar valves (pulmonary valve, aortic valve)
• Atrioventricular valves

  • Tricuspid valve separates the right atrium from the right ventricle, prevents backflow of blood into the right atrium
  • Bicuspid/mitral valve separates the left atrium from the left ventricle, prevents backflow of blood into the left atrium
• Semilunar valves

  • Pulmonary valve prevents the backflow of blood to the right ventricle
  • Aortic valve prevents the backflow of blood to the left ventricle
• The Heart

  • The human heart has four chambers: Left and right ventricle, Left and right atrium
  • The left side of the heart pumps oxygenated blood to the body while the right side of the heart pumps deoxygenated blood to the lungs where oxygen can be absorbed by the hemoglobin carrying red blood cells
  • The circulatory system is described as a double system because it has two loops
• Pulmonary circulation


  Carries deoxygenated blood from the heart to the lungs and oxygenated blood back from the lungs to the heart, ready to be pumped out to the body
• Systemic circulation


  Carries oxygenated blood to the rest of the body through the arteries and deoxygenated blood back to the heart through the veins
• Types of blood vessels

  • Artery
  • Vein
  • Capillary
• Artery


  • Thick outer wall
  • Thick inner layer of muscle and elastic fibres
  • Narrow central tube (lumen)
  • Carries blood away from the heart
• Vein


  • Thin outer wall
  • Thin inner layer of muscle and elastic fibres
  • Wide central tube (lumen)
  • Carries blood towards the heart
  • Has valves to prevent backflow
• Capillary


  • Wall is only one cell thick
  • Exchanges materials between the blood and other body cells
• Cardiac sound


  • S1 (Lubb) - caused by closure of the atrioventricular (AV) valves as ventricles begin to contract
  • S2 (Dupp) - occurs as the SL valves close at the beginning of ventricular diastole
• Blood pressure


  Depends on the speed of the blood coming into a vessel and the width of the vessel itself
• Blood pressure in different blood vessels

  • Arteries: Speed - high, Width - medium, Pressure - high
  • Capillaries: Speed - medium, Width - narrow, Pressure - medium
  • Veins: Speed - low, Width - wide, Pressure - low
• Factors affecting blood pressure

  • Age (increases as you get older)
  • Gender (men tend to have higher blood pressure than women)
  • Stress (can cause increased blood pressure)
  • Diet (salt and saturated fats can increase blood pressure)
  • Exercise (the fitter you are the lower your blood pressure is likely to be)
• Effects of high blood pressure

  Puts stress on your heart, can lead to angina, heart attacks and strokes
• Immediate effect of exercise on blood pressure

  Raises the blood pressure as the heart beats faster and more powerfully
• Long-term effect of exercise on blood pressure

  Reduces blood pressure, the fitter you are the lower your blood pressure is likely to be
• Body gets too hot


  Capillaries near the surface of the skin widen, blood is diverted to the skin where the heat can easily radiate away (vasodilation), water from the blood is excreted as sweat to cool the body
• Body gets too cold


  Capillaries near the surface of the skin get narrower, blood is diverted away from the skin to limit heat loss (vasoconstriction), sweating stops
• Heart rate (or pulse rate)


  The number of times your heart beats every minute, expressed in beats per minute (bpm)
• Maximum heart rate


  The fastest that your heart is able to beat. Can be estimated using the formula: Maximum Heart Rate (MHR) = 220 - age
• Coronary sinus


  opening in the right atrium where deoxygenated from the heart tissue is conveyed
• Blood vessel


  Simple squamous epithelium

  
• Vein


  Allows blood to flow in the correct direction

  
• Capillary bed


  collection of capillaries

  
• Covering of the heart

  Pericardium/ Pericardial membrane

  Pericardial fluid
• Pericardial fluid


  fluid secreted by the pericardial membrane

  reduces friction between heart wall and surrounding tissues when the heart is beating
• The upper chamber is called Atria/ Atrium


  The lower chamber is called ventricles
• Cardiac system


  The walls are made of cardiac muscles
• Cardiac system


  The wall dividing the left and right sides of the heart is called the septum
• cardiac system

  semi-lunar valves prevent expelled blood flowing back into the heart
• Walls of the heart

  Epicardium

  Myocardium

  Endocardium
• Epicardium


  Outer covering of the heart
• Myocardium


  thick inner layer of cardiac muscles