Year 11 Human Transport (Circulatory System) PDF

Circulatory systems A circulatory system consists of a group of organs that transport substances, such as oxygen, around the body. heart Some organisms, such as insects, have an open circulatory system, wh...

Circulatory systems A circulatory system consists of a group of organs that transport substances, such as oxygen, around the body. heart Some organisms, such as insects, have an open circulatory system, where the fluid moves freely between cells. Other organisms, including humans, have a closed circulatory system where blood is contained within vessels, where these factors can be controlled:  the speed of blood flow  the pressure of the blood  the distribution of blood in the body. 1 of 34 © Boardworks Ltd 2012  One and two circuits 2 of 34 © Boardworks Ltd 2012 Closed circulatory systems A single circulatory system has a two-chambered heart so that blood can be returned to one chamber, and pumped back out of the heart from the second chamber. This ensures blood flow in one direction only. The double circulatory system has a four-chambered heart so that blood can be pumped out to the lungs, returned to the heart, and be pumped out again to the rest of the body. This maintains a high pressure in the blood vessels and faster blood flow to the tissues. This is essential for organisms with a large body, such as whales, elephants, and humans. 3 of 34 © Boardworks Ltd 2012  Circulation The dissolved food and oxygen needed for respiration are carried around the body by the circulatory system. The circulatory system includes the blood, blood vessels, the heart and the lungs. Which part of the circulatory system actually carries dissolved food and oxygen to the body’s cells? 4 of 33 © Boardworks Ltd 2008 What does the heart do? The heart is a muscular organ located in the thorax. It pumps blood continuously around the body. The blood supplies cells with oxygen and glucose, needed for respiration. The blood also transports the waste products, such as carbon dioxide, the waste product of respiration, and urea. Special arteries called coronary arteries carry blood to the heart to supply the heart muscle cells with oxygen and glucose for contraction. 5 of 34 © Boardworks Ltd 2012  Your beating heart The heart is made of very special muscle called cardiac muscle. This is because it has to keep beating for the whole of a person’s life! If you tried to do the same action repeatedly (like the heart does), your muscles would get tired and, after a while, stop working. For example, if you keep clenching and unclenching your hand, it will get tired and may even start to get cramp. Why is it important for respiration that the heart keeps beating? 6 of 33 © Boardworks Ltd 2008 Contraction and relaxation 7 of 34 © Boardworks Ltd 2012 The Heart Which structure? 10 of 34 © Boardworks Ltd 2012 11 of 34 © Boardworks Ltd 2012  Pulse In the closed circulatory system, the blood will flow in:  arteries  capillaries  veins Each time the heart muscle contracts, it pushes blood out of the chambers at high pressure. This causes the blood vessels to throb. This is called a pulse. The pulse can be detected at various places around the body, including the wrist, at the temple and in the ear lobe. 13 of 27 © Boardworks Ltd 2012  Arteries Arteries carry blood under high pressure. They have a thick muscle wall to withstand the pressure (adaptation) A small lumen The elastic walls stretch when the heart beats and then contract back and force blood forward. (adaptation) This can be felt as your pulse Thinking point Someone has been in an accident and they are bleeding. How could you tell – just by looking – if an artery had been damaged? Just as important – if it was a damaged artery what would you do?  Arteries Answers Blood in arteries is under pressure and in a muscular elastic tube. So blood squirts out driven by the heartbeat and pulse. To seal the wound pressure must be applied and if possible the wound site should be lifted up. Blood flow in arteries Blood pressure is the main force that drives blood from the heart around the body. When the heart contracts The elasticity of the (systole), blood is fibres in the arteries pumped through the means they can expand arteries at high pressure. and allow blood through. When the heart relaxes The elastic recoil of the (diastole), the blood in arteries means they can the arteries is at a much help force the blood lower pressure. along to the arterioles. 16 of 27 © Boardworks Ltd 2012  Capillaries Capillaries are very narrow – forcing blood cells to pass in single- file Capillaries have very thin walls – about 1 cell thick – which makes it easy for substances to diffuse through (adaptation) Capillaries are the point where arteries become veins! When you fall and graze your elbow the blood oozes out – you have damaged a few capillaries. A small skin cut doesn’t bleed much for the same reason.  Veins Veins carry blood towards the heart under low pressure. They have a thin muscle and elastic wall. Veins have valves which prevents blood from flowing backwards. This is what happens when the valves get leaky. Leg muscles help! leads to Structure and function of blood vessels What is blood? Blood is a specialized liquid that circulates around the body in blood vessels. An average adult has 4–6 litres of blood. Blood has a range of functions, including to:  transport substances  defend against pathogens  control body temperature  maintain pH of fluids. 20 of 28 © Boardworks Ltd 2012 Features of red blood cells What are the specialized features of a red blood cell? flattened, biconcave disc shape: ensures large surface area to volume ratio for efficient gas exchange large amount of haemoglobin: for transporting oxygen no nucleus or organelles: maximizes space for haemoglobin, so more diameter (6–8 µm) larger than oxygen can be capillary diameter: slows blood transported flow to enable diffusion of oxygen 21 of 28 © Boardworks Ltd 2012 Haemoglobin Red blood cells are packed with haemoglobin, which is a red protein that gives blood its colour. Haemoglobin makes up 95% of the dry mass of a red blood cell. Haemoglobin is made up of four protein chains, each bound to one haem group. In the lungs, the haem group combines with oxygen to form oxyhaemoglobin. When blood reaches the organs, oxyhaemoglobin splits to reform haemoglobin and oxygen, where the oxygen is free to diffuse into cells. 22 of 28 © Boardworks Ltd 2012  What is blood? Plasma straw coloured liquid mainly water carries dissolved substances White cells two sorts both kill Red cells carry oxygen pathogens contain haemaoglobin Blood also contains platelets, hormones, digested food products, dissolved carbon dioxide Blood clotting At the site of a cut or wound the blood will clot. This prevents further blood loss, reduces the risk of pathogens entering and forms a framework for repairing the damaged tissue. Platelets rapidly stick to a damaged area, releasing chemicals that start a series of reactions. This results in a network of fibrin fibres which form a mesh. This mesh traps blood cells and debris, forming a solid clot. 25 of 28 © Boardworks Ltd 2012 Why can blood clots be dangerous? Blood clots normally occur at the site of a cut. However, they can arise within blood vessels. This can be dangerous as a clot could obstruct the flow of blood to a major organ. A blood clot can cause organ damage and even death. Anti-coagulant drugs, such as warfarin, heparin and aspirin can be taken when a person’s blood is clotting too quickly. These drugs can control clotting by reducing the ability of the blood to clot. Substances such as vitamin K, alcohol, green vegetables and cranberries can also affect clotting. 26 of 28 © Boardworks Ltd 2012 What is haemophilia? Haemophilia is an inherited disease that prevents the body from controlling bleeding properly. Haemophilia is a recessive sex-linked disease that mainly affects males. People with haemophilia (haemophiliacs) are partly or completely missing a clotting factor that is needed to make their blood clot properly. There are about 6,000 people with haemophilia in the UK. 27 of 28 © Boardworks Ltd 2012 Reduced blood flow Arteries can become blocked when fatty deposits build up. This reduces blood flow and increases the pressure. A reduced blood flow is especially dangerous in the coronary arteries, which supply the heart with oxygen and glucose. fatty deposits To restore normal blood flow, a small mesh tube called a stent is inserted into the narrow artery. The metal or fabric mesh of the stent is used to support the inner wall of the artery to keep it open artificially. 29 of 27 © Boardworks Ltd 2012 Heart rate and exercise During exercise several changes occur:  the heart rate increases  the rate and depth of breathing increases  the arteries supplying the muscles dilate. These changes help to provide oxygen and glucose to muscles and remove carbon dioxide more quickly. Heart rate can also be altered by hormones such as adrenaline. The presence of adrenaline causes the heart rate to increase, allowing a quick response to danger. 30 of 34 © Boardworks Ltd 2012  How does regular exercise affect the heart? Regular exercise can strengthen the heart, causing:  the heart to become bigger  the amount of blood pumped by the heart to increase  the walls of the heart to become thicker and stronger. The result is that the heart becomes a more efficient pump. The resting pulse rate gets slower as a person becomes fitter, because the heart needs fewer beats to pump blood round the body. 31 of 34 © Boardworks Ltd 2012 ECG in diagnosis of irregular heartbeats ECGs are used to diagnose problems with the heart, as variations in different components of the trace can indicate a disease or other abnormality. An ECG may be taken while the patient is relaxed or it may be taken before, during and after exercise. This is called a ‘stress test’ and usually involves the patient exercising on a treadmill while attached to an ECG machine. 32 of 34 © Boardworks Ltd 2012 What is an electrocardiogram? The electrical activity of the heart can be monitored by using an electrocardiograph. Several electrodes are attached to specific places on a person’s chest. These detect electrical changes in the heart by measuring current at the skin’s surface. The leads are connected to a machine that draws an electrocardiogram (ECG). A normal ECG is shown below. 33 of 34 © Boardworks Ltd 2012