Circulatory System


The circulatory system is one of the major systems in the human body and transports nutrients, wastes and hormones around the body. The heart, blood, arteries, capillaries and veins are the major structures in the circulatory system. Resources on the lymphatic system are also found on this topic page.


Online Resources               Home    Biology    Top               Previous    Next


  • 23 and 1/2 Hours – Dr. Mike Evans – 9:19 – unique and wonderfully presented video on how exercise is the best thing we can do for our health
  • Anatomy Reveal – Hybrid Medical Animation – a beautiful animation (no voiceover) showing the human circulatory system
  • Angina – Medline Plus – tutorial on angina
  • Arrhythmias – Medline Plus – tutorial on arrhythmias
  • Beating Heart – Hybrid Medical Animation – video of a beating heart with excellent graphics 
  • Blood Flow Through the Human Heart – Sumanas – excellent animation and explanation of blood flow through the heart and around the body  
  • Blood Typing – – game where students need to choose compatible blood types in a surgery
  • Congestive Heart Failure – Medline Plus – tutorial on congestive heart failure
  • Drug Eluting Stent – Hybrid Medical Animation – animation (with advertisement) that nicely shows how a stent works
  • Electrocardiogram Game – – game where students set up an electrocardiogram (ECG) on four different patients and analyse the ECG to diagnose four heart conditions – healthy, arrhythmia, infarction, blockage
  • Essential Hypertension – Medline Plus – tutorial on hypertension (high blood pressure)
  • Heart Attack – HHMI Biointeractive –video – 0:37 – that briefly explains what causes a heart attack
  • Heart Attack – Medline Plus – tutorial on heart attacks
  • Human Heart – Medtropolis – an interactive with 3 parts: 1. Heart Parts. 2. Animated Heart. 3. Narrated Tour
  • Interactive Heart – Hybrid Medical Animation – interactive with slide bar and excellent graphics of a beating heart. This is not educational but contains amazing graphics 
  • Leukemia – Medline Plus – tutorial on leukemia
  • Measuring Blood Pressure – Sumanas – nice animation on how blood pressure is measured using a cuff and stethoscope 
  • Sickle Cell Anaemia – HHMI Biointeractive – 0:59 – very nice animation that explains how a point mutation leads to phenotype changes in haemoglobin that results in sickle cell anaemia
  • Thrombosis – Hybrid – animation with voiceover explaining blood clotting 


Real World               Home    Biology    Top               Previous    Next


  • altitude sickness - a collection of non-specific symptoms caused by low oxygen levels at high altitude, commonly above 2400 metres. Symptoms resemble the flu or hangover. It can progress to high altitude pulmonary oedema (HAPE) (fluid accumulation in the lungs), the major cause of death at high altitude, or high altitude cerebral oedema (HACE) (fluid leakage in the brain), which are potentially fatal.
  • anaemia – a decrease in the number of red blood cells (RBCs) or haemoglobin that results in a reduced oxygen-carrying capacity of the blood and decreased levels of oxygen in the tissues. The three major causes of anaemia are reduced RBCs, increased RBC destruction and reduction in blood volume. Iron-defiency anemia is the most common form of anemia (half of all cases) resulting from intestinal bleeding (due to infection or ulcers) or menses and results in reduced haemoglobin production.
  • blood bank – Australian Red Cross Blood Service – an organisation that collects blood from donors and gives it to hospitals to use in surgery or emergencies to replenish the blood lost by patients (blood transfusion) or make blood products needed by sufferers of chronic blood conditions.
  • blood groups or blood types – a classification of blood based on the presence or absence of antigens on the surface of red blood cells. A total of 30 blood groups are recognised, with the most common and important groups being the ABO and Rhesus factor (+/-) blood groups. Everyone has a blood type, which is inherited from their parents. In Australia, the most common blood type is O+ (40%), followed by A+ (31%), O- (9%), A- (7%), B+ (5%), B- (2%), AB+ (2%) and AB- (1%). These numbers vary significantly from country to country. The ABO and Rh blood groups are important because each blood type can only be received by a patient with a compatible blood type. Transfusion of the incorrect blood type results in the acute haemolytic transfusion reaction (AHTR), where red blood cells are destroyed (haemolysis) by antibodies in the donor's blood, which causes acute renal failure, shock and possibly death. 20 people in the U.S. die every year from AHTR.
  • blood pressure – one of the vital signs. High blood pressure (hypertension) is one of the risk factors for stroke and heart attack and is a consequence of poor diet and lifestyle.  
  • blood transfusion – the delivery of whole blood or components of the blood (more common) such as red blood cells, white blood cells, plasma, clotting factors and platelets to recepients with medical conditions or emergency situations
  • blue babies – see hole in the heart
  • blushing – the involutary reddening of a person's face due to embrassment or emotional stress. It is caused by hyperactivity of the sympathetic nervous system. Sympathetic activation of neurons dilates capillaries in the surface of the skin, which increases blood flow and allows heat to be released, which warms the face and causes it to become red.
  • bruise – a local collection of blood (hematoma) caused by damage to blood vessels as the result of trauma allowing blood to leak into the tissues. Bruise colours are caused by the breakdown of haemoglobin in extracellular tissues. Haemoglobin (red-blue), biliverdin (green), bilirubin (yellow) and hemosiderin (golden brown) are breakdown products of haemoglobin that are cleared as the bruise disappears.
  • carotid artery - the artery that supplies the brain with blood. It is one of the most important arteries in the body. A puncture in the the carotid artery can drain the body's entire blood supply in 40 seconds.
  • cells – usually no more than 1 mm away from their nearest capillary
  • cramp – “don’t swim after you eat” – blood flow increases to your digestive system and away from your muscles so you tend to cramp more easily
  • haemophilia - a group of inherited genetic disorders that impair the body's ability to control blood clotting. Haemophilia is a recessive, sex-linked disease, inherited on the X chromosome and results in a defiency of a specific clotting factor.
  • heart attack (myocardial infarction) – caused by the blockage (most common) of a coronary artery (arteries that supply the heart itself with oxygen). The loss of blood supply (ischaemia) results in an oxygen shortage (hypoxia) and death (infarction) of cardiac muscle cells and a loss in function of the heart. Heart attacks are the number one cause of death for men and women worldwide (despite the common belief that breast cancer is the number one killer of women). Risk factors include smoking, high lipid levels (in particular high levels of triglyerides and low-density lipoproteins (LDLs)), high blood pressure (hypertension), obesity, excessive alcohol consumption and stress.
  • heart disease – cause by high cholesterol. Risk factors are familial and diet/exercise. A hgh fat diet and high cholesterol increases the risk of heart disease.
  • heart foundation tick – a symbol used by the Australian Heart Foundation to help consumers make healhier choices at the supermarket by choosing products lower in saturated fats, salt and kilojoules and higher in healthy nutrients such as calcium and fibre. Products that contain "the tick" are healthier choices compared to alternatives in their category, but are not necessarily healthy foods, e.g. certain brands of meat pie have the Heart Foundation Tick.
  • heart murmur – abnormal heart sounds (turbulent "swishing" sounds) caused by leaky valves or abnormal passages in the heart. 
  • hole in the heart
  • humans – 70 beats per minute – can measure own heart beat – pulse
  • hummingbird – up to 1260 beats per minute
  • ice cream headache (brain freeze) – vasoconstriction and vasodilation – when a cold substance (such as an ice cream or slushie) touches the roof of your mouth it causes capillaries in the sinuses to constrict and dilate quickly as they warm up. This dilation is sensed by pain receptors, which send signals to the brain. The nerve (the trigeminal nerve) that sends the message is the same nerve that senses facial pain, so the brain interprets the pain as coming from the forehead and a headache is experienced (this is an example of referred pain – pain that is caused in one area but felt in another)
  • leukemia – a cancer of the blood or bone marrow which results in an abnormal increase in immature white blood cells in the blood
  • shock – there are two common uses of the word. Emotional shock (otherwise known as acute stress reaction) occurs in response to a traumatic event. Stress results in activation of the sympathetic nervous system and release of epinephrine (adrenalin) and to a lesser extent norepinephrine (noradrenalin) from the adrenal glands on top of the kidneys. Adrenaline triggers increased heart rate, increased breathing and constriction of blood vessels. Medical shock is a medical emergency that occurs due to a lack of oxygen in the blood and results in low blood pressure, increased heart rate and signs of poor circulation. Shock is a common end point in many medical conditions and there are five main causes: hypovolemic (loss of blood volume - most common), distributive (dilation of blood vessels resulting in reduction of blood flow to organs), cardiogenic (heart failure), obstructive (blockage of blood vessels), endocrine (hormone effects).
  • stroke – a rapid loss in brain function due to a loss in blood supply to the brain. The FAST acronym (Face, Arms, Speech, Time) can help you tell whether someone is having a stroke. One side of the face may droop, one arm may stop working, speech may become slurred and you need to get medical attention quickly.
  • Viagra – sildenafil citrate – a vasodilator that increases blood flow to the penis and causes an erection
  • warfarin – a blood thinner now used in medicine but originally used in warfare


Key Knowledge               Home    Biology    Top               Previous    Next 


  • red blood cells
    • haemoglobin – transports oxygen
    • carbonic anhydrase – an enzyme that catalyses the reaction: CO2 + H2O --> H2CO3 --> HCO3- + H+ and controls the pH of the blood
  • white blood cells
    • immune defence
  • platelets
  • plasma
  • the flow of blood around the body – oxygenated blood leaves the aorta and travels via arteries and arterioles to the capillaries where oxygen and carbon dioxide are exchanged with the cells in the body. Deoxygenated blood returns to the heart via venules and veins and empties into the right atrium. The right atrium pumps deoxygenated blood into the right ventricle, which pumps blood to the lungs via the pulmonary arteries. Oxygen and carbon dioxide are exchanged in the lungs and oxygenated blood returns to the heart via the pulmonary veins and empties into the left atrium. The left atrium pumps oxygenated blood into the left ventricle, which pumps blood via the aorta to the rest of the body.
  • heart
    • anatomy
      • 4 chambers
        • left atrium
        • left ventricle
        • right atrium
        • right ventricle
        • function – the role of the heart – to pump oxygenated blood to the cells of the body and return deoxygenated blood to the lungs
        • the heart functions as two pumps – the right side of the heart pumps blood to the lungs and the left hand side pumps blood to the body
  • arteries – travel away from the heart
  • veins – travel towards the heart
  • thrombosis – the formation of a blood clot (thrombus)
  • occlusion – the blockage of a vessel
  • vasoconstriction – constriction of blood vessels
  • vasodilation – dilation of blood vessels


Topic Ideas               Home    Biology    Top               Previous    Next


  • question – why do plants and animals need circulatory systems? (1 mark, diffusion is not efficient enough to support the needs of every cell in the organism)
  • question – arteries always carry oxygenated blood – true or false? Give an example (false, pulmonary artery)
  • DVD – “Anatomy for Beginners” – circulatory system
  • diagrams and colours – colour a blank heart and indicate direction of flow
  • excursion – blood bank
  • model – heart
  • heart dissection
  • activity – circulation activity – give students an empty diagram of the human circulatory system and provide the definitions and clues to fill in the diagram


Images               Home    Biology    Top               Previous    Next 


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