Blood circulatory system

• Main functions of blood


  • Transport
  • Protection
• Transport


  Red blood cells transport oxygen, plasma transports dissolved substances
• Protection


  White blood cells destroy germs/microbes/pathogens/bacteria/viruses that enter the body
• Haemoglobin in red blood cells is rich in iron
• Plasma


  A straw-coloured (pale yellow) liquid of the blood, 90% of which is water
• Substances dissolved in plasma

  • Digested food (nutrients)
  • Sugars
  • Salts
  • Carbon dioxide
  • Wastes (such as urea)
  • Hormones
  • Antibodies
  • Other proteins
• Antibodies are proteins that certain white blood cells produce when infected with bacteria or viruses, to destroy them and protect from infections
• Red blood cells


  • Contain large quantities of haemoglobin to bind oxygen
  • Don't have a nucleus, so more room for haemoglobin
  • Have a biconcave disc shape to allow quick oxygen movement
  • Are tiny and flexible to squeeze through narrow blood vessels
• People living at high altitudes have greater amount of red blood cells than people living at low altitudes (sea-level) to compensate for lower oxygen levels
• Athletes training at high altitudes develop the capacity to run at low oxygen level, and perform better at low altitudes
• White blood cells


  • Have a nucleus
  • Have no pigments
  • Are larger and fewer in number than red blood cells
  • Increase in number during infections to destroy germs rapidly
• Types of white blood cells

  • Phagocytes (engulf and digest pathogens)
  • Lymphocytes (produce antibodies to destroy pathogens)
• Stopping bleeding


  1. Platelets produce fibres to trap red blood cells

  2. Blood changes into a thick red jelly called a blood clot

  3. The clot hardens to a scab, sealing the cut and preventing germs from entering
• Types of blood vessels

  • Arteries
  • Capillaries
  • Veins
• Blood vessels


  • All have lumens (hollow openings)
  • Arteries branch into tiny capillaries
  • Capillaries join to form veins
  • Capillaries are thin to allow gas exchange, arteries are tough and flexible for high pressure, veins have valves to prevent backward blood flow
• Heart


  A muscular organ about the size of a fist, located in the center of the chest cavity, slightly inclined to the left, made of cardiac muscles, functions to pump blood through the cardiovascular system
• Pulse


  A pressure wave that expands and recoils the artery when the heart contracts/beats, palpated at many points throughout the body, measured in beats per minute
• Factors influencing resting pulse rate

  • Physical condition
  • Age
  • Weight
  • Heart disease
  • Medications
  • Smoking
  • Emotional state such as stress
• Cardiovascular diseases (CVDs)


  A group of disorders of the heart and blood vessels
• Cardiovascular diseases


  • Coronary heart disease (CHD) - disease of the blood vessels supplying the heart muscle; leading to heart attacks
  • Cerebrovascular disease or Stroke - disease of the blood vessels supplying the brain
• Heart attacks and strokes

  Usually acute events and are mainly caused by a blockage of the blood vessels and prevents blood from flowing to the heart or brain
• How Arteries Get Blocked

  1. Animal foods contain lots of fats and cholesterol

  2. Cholesterol or fatty deposits can stick to the walls of an artery and stay there, narrowing the passage of the artery. This condition is called atherosclerosis

  3. Overtime, the artery can be completely obstructed by more fatty deposits and/or blood clots

  4. The blockage is called a thrombosis
• Coronary artery


  An important blood vessel that supplies nutrients and oxygen to heart muscles
• A thrombosis in the coronary artery of the heart


  Will lead to a heart attack
• A thrombosis in blood vessels in the brain

  Results in a stroke. A stroke also occurs when the blocked artery bursts or ruptures
• When an artery is partially blocked

  Heart muscles or brain cells receive little food and oxygen
• Angina


  Severe chest pains, a warning sign that you could be at risk of a heart attack
• When brain cells do not receive enough nutrients or oxygen


  They die. A stroke may occur and can be fatal
• These problems can be avoided by adopting a proper lifestyle
• Adopting a healthier lifestyle since young age is the best option
• Risk Factors for Cardiovascular Diseases

  • Stress
  • Tobacco use
  • Foods rich in animal fats and cholesterol
  • Obesity
  • Physical inactivity
  • Harmful use of alcohol
  • Hypertension
  • Diabetes
  • Raised blood lipids
  • High salt intake
  • Being male
• Cessation of tobacco use, reduction of salt in the diet, consuming more fruits and vegetables, regular physical activity (30 minutes of exercises per day) and avoiding harmful use of alcohol have been shown to reduce the risk of cardiovascular disease
• Drug treatment of diabetes, hypertension and high blood lipids may be necessary to reduce cardiovascular risk and prevent heart attacks and strokes
• Many people have realized the importance of combining mediation, healthy nutrition and exercises in their daily lives