Biology Unit 5.2: Transport In Humans

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Unit 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 charge of blood in the human body. Blood travels through veins, capillaries and arteries and valves are put into place to ensure the blood flows one way.

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.

Double circulation is comprised of two circuits: a circuit that links the heart and the lungs, and a circuit that links the heart and the rest of the body. Blood is pumped at a low pressure to the lungs because it only flows in one direction to one place (the lungs). Blood is pumped at a high pressure to the rest of the body because there are many different organs the blood must reach, and blood being pumped at high pressure will allow it to travel to those organs. 

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

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The heart is split into two sides: the right and left. Blood always enters through the top half of the heart first. These are called atria (single = atrium). Deoxygenated blood from the body enters the heart through the right atrium and exits through the right ventricle. That blood travels to the lungs to pick up oxygen, entering the heart again through the left atrium. It exits out of the left ventricle and is pumped to reach organs in the body. The valves set in place are there to ensure the blood maintains its one-way flow.

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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 the blockage of arteries by fatty deposits. This blocks blood flow, so organs, like the heart, can't get oxygen. All organs need oxygen to survive, so if the heart isn't getting oxygen it won't work properly. Causes of coronary heart disease include poor diet, smoking and stress.

To prevent this disease, you can change your diet to a healthier one, exercise regularly, and not smoke. 

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

Atria and ventricles have muscular walls that allow them to pump blood when the walls contract. The walls contract, squeezing the chambers and pushing the blood out of it; this is the mechanism of blood being pumped. The valves open and close to control where blood flows to. 

6. Investigate the effect of physical activity on pulse rate

When you do more physical activity, your heart beats faster. This is because your muscles need more oxygen to function, so the red blood cells in your blood must obtain more oxygen and supply it to the muscles. During this, arteries that supply blood to the muscles dilate. Blood flow increases, increasing the flow of glucose and oxygen; the rate of removal of carbon dioxide also increases.

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

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

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The body contains arteries and vessels. Arteries have thick walls and thick layers of muscle and elastic fibres; this allows blood to be pumped at a higher pressure. Arteries pump blood away from the body and to the different organs.

Vessels have thinner walls and thinner layers of muscle and elastic fibres. The blood being pumped through vessels is at a lesser pressure. Vessels pump blood towards the lungs. 

Organ	To	From
Heart	Vena cava	Aorta
Lungs	Pulmonary artery	Pulmonary vein
Liver	Hepatic artery	Hepatic vein
Kidney	Renal artery	Renal vein

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

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I've mentioned arteries and veins, but what are capillaries? Capillaries are branches of the artery. Their walls are one cell thick, they're extremely narrow, and they reach body cells. Oxygen and glucose easily diffuse through the capillaries to cells, and carbon dioxide and other waste easily diffuse in to the capillaries. Arteries split into capillaries, and they join back up into veins. 

From the diagram you can see what makes up arteries, veins, and capillaries. The artery is noticeably less wide than the vein, as the narrowness allows the blood to be pumped at a high pressure.

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

Arteries are more elastic because when the ventricle contracts, blood flows through the arteries and is pumped at a high pressure to reach organs. They are deeper in the flesh than veins and the pulse from them is detectable. 

Veins are less elastic because the blood flowing in them doesn't need to be at a high pressure. They are near the surface of the skin because they can get rid of heat if the body becomes too hot (you'll learn more about this in the homeostasis unit). The pulse from veins is not detectable because blood is not pumped at a high pressure. 

Capillaries are thin, as mentioned above, so substances can easily diffuse in and out of them.

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

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Blood is made up of these three things: red blood cells, white blood cells, and platelets.

Red blood cells transport oxygen and carbon dioxide around the body. They are red because of a pigment called haemoglobin. Oxygen binds to haemoglobin after it is picked up from the lungs. Red blood cells are disk-like. They contain no nuclei to maximise the storage of oxygen.

White blood cells protect the body against diseases and viruses. There are two types of white blood cells: lymphocytes and phagocytes. When a pathogen (virus) enters the body, lymphocytes produce chemicals that make them stick together, dissolve, or destroy the toxins pathogens produce, called antibodies. Phagocytes then engulf the pathogens; they are digested and then killed. 

Platelets are fragments of red blood cells that help blood clot. They are made in bone marrow, along with other blood cells. When you get a cut, platelets come in contact with air, turning a protein called fibrinogen into threads of fibrin. These threads make a net over the cut. Red blood cells get caught in the net, creating a blood clot. The clot dries to form a scab, and new skin grows underneath the scab. Without platelets, it would be easier for pathogens to get into the body.

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

Along with the cells, plasma makes up blood. Plasma is a liquid that carries dissolved substances around the body, such as nutrients, hormones, and waste materials. 

13. 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.

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

Antibodies are produced by lymphocytes to help the body get rid of pathogens. 

Tissue rejection is when the body recognises that a foreign organ donor is not originally part of the body. The body then rejects the organ. 

Phagocytosis is the name for when phagocytes engulf pathogens, destroying them to keep the body healthy.