B5 – transportation 2 – 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 main transport system of all mammals is the blood system, also known as the circulatory system;

  • It is a network of tubes , called blood vessels;

  • A pump, the heart, keeps blood flowing through the vessels;

  • Valves in the heart and veins prevent backflow of blood.

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.


  • Blood passes through the heart twice for each complete circulation of the body;

  • The right side of the heart collects deoxygenated blood from the body and pumps it to the lungs;

  • Thus there is a low pressure circulation in the lungs;

  • The left side collects oxygenated blood from the lungs and pumps it to the body;

  • Thus there is a high pressure circulation to the body tissues.

  • The double circulatory system helps to maintain blood pressure, making circulation efficient.

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


  • The heart is a pump, made of muscle, which moves blood around the body;

  • The muscle is constantly active and coronary arteries to provide it with oxygen and glucose;

  • The left and right side of the heart is completely separated from each other by a septum;

  • RIGHT side receives deoxygenated blood from the body and pumps it to the lungs for oxygenation;

  • LEFT side receives oxygenated blood from the lungs and pumps it to the body;

  • There are four chambers - two atria and two ventricles;

  • The right atrium (RA) receives blood from vena cava and the left atrium (LA) from pulmonary vein.

  • Both atria then squeeze the blood into the ventricles;

  • The tricuspid valve allow blood to flow from RA to right ventricle and the bicuspid valve allow blood to flow from LA to left ventricle preventing backflow;

  • The right and left ventricles then squeeze the blood into arteries;

  • Right ventricle (RV) pumps blood into the pulmonary artery & the left ventricle (LV) into the aorta;

  • The semilunar valves allow blood to move into the arteries and prevent backflow

  • The wall of the LV is much thicker than the RV because it needs to build up enough pressure to send the blood to all the main organs (not just to the lungs).

  • Thus the blood in the aorta has a much higher pressure than in the pulmonary artery.

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

  • Coronary arteries supply blood (nutrients and oxygen) to the heart muscles.

  • If a coronary artery gets blocked (e.g. by a blood clot), the cardiac muscle runs short of oxygen;

  • Blockage of the coronary arteries is called coronary artery disease;

  • The cardiac muscle cannot respire, so it cannot obtain energy to contract;

  • The heart therefore stops beating; this is called a heart attack or cardiac arrest.



Preventive measures

Poor diet with too much saturated fat

Cholesterol builds up in the arteries – this can block it eventually

Cholesterol-free diet


Nicotine damages the heart and blood vessels

Stop smoking


Increase blood pressure - this can result in fatty materials collecting in the arteries

Find ways of relaxing, identify the causes of stress & avoid them

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

  • Heart beats as the cardiac muscles in its walls contract and relax;

  • When they contract, heart becomes smaller, squeezing blood out. This is called systole;

  • When they relax, the heart becomes larger, allowing blood to flow into the atria and ventricles. This is called diastole;

  • The rate at which heart beats is controlled by a patch of muscle in the right atrium called pacemaker;

  • The pacemaker sends electrical signals through the walls of the heart, which make the muscle contract;

  • Between atria and ventricles are atrio-ventricular valves (bicuspid on left & tricuspid on right);

  • When the ventricles contract, these valves stop blood flowing back into atria;

  • As the ventricles contract, the blood pushes the semilunar valves upwards;

  • The tendons attached to them stop them from going up too far.

  1. Investigate the effect of physical activity on pulse rate.

IGCSE Biology (Jones & Jones), p.88, activity 8.1 ‘to find the effect of exercise on the rate of heartbeat’.

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

  • Heart beats about 70 times a minute, more if you are younger;

  • The rate becomes lower the fitter you are;

  • During exercise the heart rate increases to supply the muscles with more oxygen and glucose;

  • These are needed to allow the muscles to respire aerobically, so they have sufficient energy to contract;

  • Regular exercise is needed to keep the heart muscle in good tone;

  • This results in the heart being more efficient in maintaining blood pressure and reduces the risk of coronary heart disease.

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





Vena cava and pulmonary vein

Pulmonary artery and aorta


Pulmonary artery

Pulmonary vein


Hepatic portal vein & hepatic artery

Hepatic vein


Renal artery

Renal vein

  1. Describe the structure and functions of arteries, veins and capillaries.

  2. Explain how structure and function are related in arteries, veins and capillaries.

Blood vessel


How structure is related to function


1.Thick, tough wall with muscles and elastic tissue,

2. Narrow lumen

3. Valves absent

1. Thick walls to withstand and maintain blood pressure (prevents bursting).

2. Narrow lumen maintains high blood pressure.

3. High pressure prevents backflow of blood.


1. Thin wall with less muscles and elastic tissue

2. Large lumen

3. Valves present

1. Thin walls allow muscles to exert pressure on the veins.

2. Wide lumen allows great volume of blood to pass or reduces resistance to blood flow.

3. Valves prevent backflow of blood.


1. Permeable wall (one cell thick) with no muscle and elastic tissue

2. Lumen approximately one red blood cell wide

1. One cell thick wall allows diffusion of materials between capillary and surrounding tissues.

Pores in the wall allow white blood cells to exit.

2. Narrow lumen allows blood cells to pass through slowly and increases oxygen diffusion from red blood cell.

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


Blood platelets

Red blood cell

White blood cell

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

  2. State the functions of blood.

Components of blood


1. Red blood cells

Red due to hemoglobin which carries oxygen and transports it to the tissues.

2. White blood cells

Fights infection by phagocytosis and antibody production.

3. Platelets

Causes blood clotting.

4. Plasma

Transport of blood cells, ions, soluble nutrients, hormones & carbon dioxide.

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

  • The immune system is the body’s defence against disease and foreign bodies. There are two main types of white blood cells – lymphocytes & phagocytes:

Antibody production:

  • All cells have proteins on their surface called antigens;

  • Lymphocytes recognize foreign antigens from foreign cells (such as bacteria) and make antibodies to them;

  • A different antibody is produced for each antigen;

  • Antibodies make bacteria clump together in preparation for action by phagocytes or neutralize the toxins produced by the bacteria;

Tissue rejection:

  • Transplants involve replacing a damaged organ with a donor organ;

  • However lymphocytes detect the foreign antigens of the donor organ and make antibodies to it;

  • The donor organ is rejected as antibodies ‘fight’ the foreign tissue;

  • To prevent this happening:

(i) The donor organ needs to be a similar tissue type to the patient e.g. from a close relative;

(ii) Immunosuppressive drugs are used, which switch off the body’s immune response;

  • However the drawback of this drug is that the patient needs to be kept in isolation as they are at the risk of dying from any disease they are exposed to.


  • Phagocytes have the ability to move out of capillaries to the site of infection;

  • They then engulf (ingest) the infecting pathogen and kill them by digesting them. A process called phagocytosis.

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