IGCSE Coordinated Science: Transport in Humans

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5.2 Transport in Humans

1 Describe the circulatory system as a system of tubes with a pump and valves to ensure one-way flow of blood.

The circulatory system is the system in which blood is pumped around the body. We need this system to transport oxygen and nutrients to our body cells for respiration.

Valves are devices that controls the direction of the flow of blood and in the body, the valve ensures that the blood flows one way. They achieve this by closing and opening to prevent blood from flowing both ways.


2 Describe double circulation in terms of a low pressure circulation to the lungs and a high pressure circulation to the body tissues and relate these differences to the different functions of the two circuits.

The body contains a “double circulatory system”, where one circuit pumps blood to the lungs, where oxygen is acquired and Carbon Dioxide is released. When the body acquires oxygen, it is said to be Oxygenated. 

The Oxygenated Blood then enters the second circuit, which takes oxygen both to the brain and the entire body.

In IGCSE Coordinated Science, we are supposed to describe this process in terms of “pressure”. When blood is transported from the heart to the lungs, the pressure it travels at is relatively smaller than the second circuit, where the blood is transported from the heart to the rest of the body.


Its very simple. The first circuit only requires blood to be pumped to the lungs. However, the second circuit     requires blood to be pumped across the ENTIRE body, so naturally, the second circuit will require the blood to  be pumped at a much higher pressure in order to pump the blood across a number of places.







3 Describe the structure of the heart including the muscular wall and septum, atria, ventricles, valves and associated blood vessels.

Heart image

This is a two dimensional view of the heart.  The heart has four chambers, two atria and two ventricles. From a perfunctory glance, you might ask why is the left side of the heart, the right side, and why is the right side of the heart the left side? Just imagine looking at your own heart in a mirror, and you’ll see what they did.

The sides of the heart are separated by the septum. Each side of the heart contains an atrium and a ventricle, atrium at the top, ventricle on the bottom, and there is a Valve between the atrium and ventricle of each side. On the left, the valve is called the Bicuspid valve, and on the right, the Tricuspid valve.

There are four major blood vessels associated with the heart:

  • Pulmonary Veins: This transports oxygenated blood from the lungs to the left atrium
  • Aorta: This transports oxygenated blood from the heart to the rest of the body and the brain.
  • Vena Cava: This transports deoxygenated blood from the rest of the body to the heart.
  • Pulmonary Artery: Transports deoxygenated blood to the heart to the lungs.


4 Describe coronary heart disease in terms of the blockage of coronary arteries and state the possible causes (diet, stress and smoking) and preventive measures.

Coronary Heart Disease is a heart disease where certain parts of the “coronary artery” becomes “clogged” with cholesterol , and substances such as oxygen and nutrients cannot be transported across the body.

File:Heart attack diagram.png

If not properly treated, a blood clot may form near the partially “clogged” area, completely blocking the artery. No oxygen or nutrients is able to be transported around the body, little/no respiration is able to occur, that part of the heart dies, and the victim gets a heart attack, which is extremely fatal.

Possible Causes of Coronary Heart Disease

  • Lack of exercise
  • Diet high in fat and cholesterol
  • Diabetes
  • High Blood Pressure
  • Genetics
  • Stress
  • Smoking


5 Describe the function of the heart in terms of muscular contraction and the working of the valves.











When the heart is being filled with blood, we call this Diastole. When the heart is pumping blood out, we call this Systole.

During Diastole, the blood first enters the atria, the atria contracts for force blood into the ventricles, both the tricuspid and bicuspid valves are opened to allow blood into the ventricles. The semi-lunar, however, is shut.

Once the ventricles are filled with blood, Systole happens. The bicuspid and tricuspid valves shut and semi-lunar valves open. The ventricles contract to force blood into the aorta and pulmonary arteries.

During diastole, the semi-lunar valves are shut to keep the blood out of the arteries. However, during systole, the tricuspid and bicuspid valves are closed to prevent blood from flowing back into the atria when it opens. The tricuspid and bicuspid valves are made out of tendons, and then prevent blood from following backwards and make sure blood flows only in one direction.

6 Investigate the effect of physical activity on pulse rate.

Physical activity increases pulse rate.


7 Investigate, state and explain the effect of physical activity on pulse rate.

With exercise or physical activity, the heart rate increases to supply the muscles with more oxygen to produce extra energy. The heart can beat up to 200 times per minute with extreme exercise. The brain sends nerve signals to the heart to control the rate. The body also produces chemical hormones, such as adrenaline, which can change the heart rate. When we are excited, scared, or anxious our heart gets a signal to beat faster. During a fever, the heart beats faster to bring more blood to the surface of the body to release heat and cool the body. The heart rate increases during and after a meal to send more blood to the digestive system. A trained athlete’s heart can pump more blood with each beat so his or her heart rate is slower. Likewise, an athlete’s recovery time is shorter.


8 Name the main blood vessels to and from the heart, lungs, liver and kidney.

We did this question previously somewhere, so i’ll just copy and paste it.

  • Pulmonary Veins: This transports oxygenated blood from the lungs to the left atrium
  • Aorta: This transports oxygenated blood from the heart to the rest of the body and the brain.
  • Vena Cava: This transports deoxygenated blood from the rest of the body to the heart.
  • Pulmonary Artery: Transports deoxygenated blood from body to the heart to the lungs.
  • (Common) Hepatic Artery: This supplies oxygenated blood to the liver (also pylorus (part of stomach), duodenum and pancreas).
  • Hepatic Portal Vein: This transports blood from the gastrointestinal tract and spleen to the liver, rich in nutrients to be processed by the liver.
  • Renal Artery: This supplies kidney with oxygenated blood.
  • Renal Vein: This transports blood away from the kidney, into the inferior Vena Cava.


9 Describe the structure and functions of arteries, veins and capillaries


File:Endothelial cell.jpg













The artery is responsible for transporting blood away from the heart to the lungs and the rest of the body.

The blood in the arteries is transported at a high pressure. The heart pumps the blood very quickly into the arteries. Each time the ventricle contracts, the pressure in the arteries increases, and when the ventricle relaxes, pressure in the arteries decrease

The artery also has a very narrow lumen with a small diameter, which allows blood to flow through at a higher pressure.

Additionally, arteries have a nice strong thick outer wall to withstand the high pressure in which blood is transported


The vein transports blood towards the heart.

  • Travels with very low pressure
  • Lumen is wide to facilitate with the low pressure in which blood travels at.
  • Thin, inelastic walls as they do not need to transport blood at such as high pressure.
  • Have valves: Since blood travels so slowly with a low pressure, it runs the risk of of blood backflow, especially in veins where the blood is moved upwards against gravity. When muscles squeeze the blood, the valves open to allow the blood to enter. When the muscle relaxes, the valves close to prevent the backflow of blood.






















  • Smallest blood vessels
  • The function of capillary is to get blood from the arteries as close to as possible to the tissues in order to exchange material with the cells.
  • Links arteries with veins

When arteries go near an organ, it divides into arterioles. These arterioles divide into several more blood capillaries that go through the tissue.

The capillaries are adapted to their jobs:

  • One cell thick: Reduce diffusion distance and allows more efficient exchange of materials.
  • Pores in their walls between the cells: Allow plasma to get out of the blood and become tissue fluid.


11 Identify red and white blood cells as seen under the light microscope on prepared slides, and in diagrams and photomicrographs.

Red Blood Cells

  • Red in color
  • Bioconcave Disk Shape
  • No nucleus

White Blood Cells

  • Bigger than Red Blood Cells
  • Exist in fewer amounts than Red Blood Cells
  • Have a nucleus


11 List the components of blood as red blood cells, white blood cells, platelets and plasma.

The components that exist in the blood are

  • Red blood cells
  • White Blood cells
  • Platelets
  • Plasma


12 State the functions of blood:

Red blood cells – haemoglobin and oxygen transport.
White blood cells – phagocytosis and antibody formation,
Platelets – causing clotting (no details),
Plasma – transport of blood cells, ions, soluble nutrients, hormones and carbon dioxide.


13 Describe the immune system in terms of antibody production, tissue rejection and phagocytosis.


White blood cells produce lymphocytes, which creates antibodies which dissolve the toxins of the bacteria.

Tissue Rejection

During Organ Transplant, Lymphocytes become a serious problem. E.g. if someone with kidney failure receives a kidney from someone else, the cells of the kidney will have different antigens than the other cells in the patient’s  body. The lymphocytes will view these cells as how they view bacterial cells and they will start attacking them. We call this tissue rejection.


This is where the white blood cells produce something called “Phagocytes’. When lymphocytes finish dissolving the toxins of the bacteria, Phagocytes finish off the job by “engulfing” the bacteria.








18 thoughts on “IGCSE Coordinated Science: Transport in Humans

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  2. Revy

    5.2.3 “Pulmonary Artery: Transports deoxygenated body to the heart to the lungs.” shouldn’t this be “Pulmonary Artery: Transports deoxygenated BLOOD to the heart to the lungs.”?
    no offense, just trying to correct some of your mistakes you make, if not, let me know, as body doesnt make too much sense to me^^ 😀

    ps: THANKS for this awesome website, helps me out with revision for IGCSEs :)

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  4. Joyce

    Just a heads up, I was revising using your website and number 8 seems to be lacking detail about the main blood vessels leaving and entering : liver and kidney.
    Keep up with the amazing progress you have, the best IGCSE science website yet!

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  6. Shreeansh

    Surely you mean that the arteries are nearer to the surface because they have a higher pressure (which we feel as pulse) and the veins are more inside the flesh?

    1. Andrew Chan

      Shreeansh, that is a very logical way of looking at this, however that is not true. With veins (you might or might not need to know this) being categorized into two types, deep and superficial, one can tell that the deep vein is deeper inside the flesh than the superficial one, hence the name. The deep vein is usually paired with an artery, while the superficial is not. So why are superficial veins closer to the surface? Because their function is to help the transfer of heat away from the body, so as to facilitate cooling to make sure the body doesn’t over heat. When the body is too hot it shunts blood from the deep veins into the superficial veins, in turn losing heat near the surface. Hope this helps!

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