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Series 8 15 Blood is vital for life. It carries oxygen, nutrients and hormones to the body via a network known as the circulatory system. This system also helps heal wounds, fight infections and take away wastes. Powered by a remarkable pump known as the heart, some people fail to keep their circulatory system in good condition. Brain common carotid artery jugular vein subclavian artery subclavian vein axillary vein superior vena cava In ancient times people tried to figure out the heart and the circulatory system. The ancient Egyptians thought the heart pumped blood to convey fluids and even order to the body, but did not realise that the blood circulated. Ancient Greek physician Galen (about AD129-210) believed the system was responsible for pumping pneuma, a vital spirit in the air, around the body. He also believed the liver manufactured the blood and carried nutrients around the body. In 1628 English physician William Harvey published his book William Harvey De Motu Cordis et Sanguinis in Animalibus ( An Anatomical Exercise Concerning The Motion Of The Heart And Blood In Animals ). In this book he explained how simple experiments showed that blood circulated throughout the body pumped by the heart. Italian doctor Marcello Malpighi (1628-1694) would complete the picture by discovering the role of the capillaries. He was also the first person to see red blood cells and discover that they gave blood its colour. cephalic vein pulmonary artery pulmonary vein azygos vein heart brachial vein inferior vena cava descending aorta mesenteric artery testicular/ ovarian artery Heartbeat sequence kidney basilic vein renal artery renal vein radial artery common iliac artery common iliac vein palmer arterial arch Full right atrium palmer venous arch Inferior vena cava digital veins of the hand femoral artery digital arteries of the hand femoral vein great saphenous vein arterial network of the knee protective outer layer venous network of the knee digital arteries of the foot tricuspid valve mitral valve Right ventricle Left ventricle descending aorta Myocardium (heart muscle) muscle layer Full left atrium inner lining 2 Full right ventricle Full left ventricle In the diastole phase the atria and ventricles relax, allowing blood to flow from the atria to the ventricles. Deoxygenated blood flows to the lungs 3 Open aortic valve Contracted ventricle In the systole phase the ventricles contract, forcing blood into the pulmonary artery and aorta. PLATELETS A doctor takes a patient’s pulse There are three kinds of blood vessels: 1. Arteries Carry blood from the heart to the rest of the body. They have a thick layer of muscle to cope with the high pressure. 2. Veins Carry blood from the body back to the heart. Thinner than arteries, veins have valves inside to stop the blood flowing away from the heart. 3. Capillaries Carry blood between arteries and veins, forming a platelets web through body tissue to allow oxygen and nutrients to filter out to all parts of the body. The capillaries are the most numerous vessels red and the thinnest. The walls are just one cell thick, which makes them blood leaky enough to allow the nutrients and oxygen to get through. cells s Platelet concentrates shown under a microscope outer layer Did you know? direction of blood flow 3 red blood cells n It was once believed that the heart was the centre of all emotions. We still refer to the heart when talking about emotions. n If you put all of the blood vessels in an adult human body end to end they would wrap around the Earth four times. n Blood cells are created in the bone marrow. Each cell has a lifespan of about 120 days. Red blood cells contain no nucleus and therefore have no DNA. Get your students involved in the Olympic experience with The Daily Telegraph’s new resource kit If an injury occurs platelets, the smallest blood cells, help to stop bleeding by plugging the broken blood vessel wall and releasing chemicals that promote clotting. RED BLOOD CELLS s Red blood cells These pigmented cells also called erythrocytes contain haemoglobin, which contains iron that attracts oxygen. These give blood its red colour. The cells have a large surface area to absorb oxygen from the lungs but are flexible enough to squeeze through small blood vessels (some measuring as little as 0.005 mm or 5 micrometers). WHITE BLOOD CELLS There are five main types of white blood cell, neutrophils, eosinophils, lymphocytes, basophils and monocytes. They all have particular roles to play. Some, known as phagocytes, destroy foreign organisms. white blood cells valve flap cell nucleus Contracted left atrium Oxygenated blood from left lung 2 Oxygenated blood flows to the uPper and lower body Blood vessels inner lining capillary wall Aorta Contracted right atrium Flowing through the network of veins, arteries and capillaries that make up most of the circulatory system is the blood. Blood is composed of: 1 n When blood carries plenty of oxygen it becomes bright red. The blue colour of veins is due to the fact that they are carrying little or no oxygen. digital veins of the foot aortic valve The pumping of the heart, or more specifically the opening and closing of heart valves, creates waves of movement in the arteries that can be felt as a throbbing. This is known as a pulse. The best places to feel this are an artery in the wrist and the carotid artery in the neck. The pulse is useful for checking to see if a person has a normal blood circulation. Pulse rates vary according to how active the body is, but emotional excitement can also make the pulse rate race. Pulse rates also vary from person to person and even according to age. A baby’s pulse rate per minute at rest can be between 110 and 140, an adult’s between 50 and 85. elastic layer n About 98 per cent of the entire length of the circulatory system is made up of capillaries. dorsal vein of the foot Pulmonary veins Blood muscle layer Did you know? posterior tibial artery dorsal artery of the foot Right atrium Pulse peroneal artery posterior tibial vein LEft atrium inferior vena cava Oxygen-poor blood enters the heart from the superior and inferior vena cava. anterior tibial artery Sometimes, when blood flow is restricted to an area of the body, a person can experience numbness and then a prickling or tingling sensation called paraesthesia, also known as “pins and needles”. This happens because the nerves, which provide information for the sense of touch to the brain, are deprived of blood, resulting in that area of the body losing this sense. When the blood returns the nerves begin sending messages again, giving that tingling feeling. Cutting off the circulation for long periods can cause damage. Persistent feelings of tingling may indicate nerve damage. and pumps it to the lungs. Oxygen-rich blood coming from the lungs then enters the left side of the heart where it is pumped around the body. The heart is made up of long thin fibres of muscle that beat in time with each other according to a natural pacemaker in the right atrium. Superior vena cava 1 anterior tibial vein Pins and needles Pulmonary artery ulnar artery testicular/ ovarian vein small saphenous vein A doctor takes a patient’s blood pressure Pulmonary artery pulmonary valve Although it is only the size of a fist, the heart pumps blood around a system of blood vessels that measures about 50,000km. It has four chambers, a left and a right atrium and a left and right ventricle. The chambers on the right side take in blood from the body that is low in oxygen brachial artery Blood pressure Blood pressure is a measure of how much the blood pushes on the walls of vessels in the circulatory system. It is usually measured using a stethoscope and a sphygmomanometer and is recorded using a two-number system, for instance 120/80. The first number is the systolic blood pressure, the pressure in the arteries as the heart pumps it out. The second number is the diastolic, the pressure in the arteries when the heart relaxes after pumping. Blood pressure varies according to what the body is doing. If blood pressure is too high or too low it can cause problems. High blood pressure, or hypertension, has many causes but a common one is blockage of the arteries. It can cause serious problems such as heart attack. Low blood pressure, or hypotension, is often caused by a loss of blood or other fluids or vasodilation, widening of the blood vessels. It can cause dizzy spells, fainting, shortness of breath and even seizures. Aortic arch superior vena cava The heart hepatic vein hepatic artery Inside the heart axillary artery Aortic arch Discovering circulation Circulatory system THE PLASMA Blood is about 55 per cent plasma. A yellowish liquid, plasma consists mostly of water but 10 per cent is nutrients including glucose, salts, hormones and proteins. One of the proteins is fibrinogen, which has a key role in blood clotting. plasma Find out more Sources and further study: DK E.explore Human Body by Richard Walker (DK) Encyclopedia Of The Human Body by Richard Walker (DK) Cambridge Illustrated History: Medicine edited by Roy Porter (Cambridge) The Human Body (BBC DVD) Encyclopaedia Britannica Editor: TROY LENNON Designer: PAUL LEIGH FOR DETAILS GO TO www.news.com.au/dailytelegraph/classmate Tuesday 11.30am on