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8 Humans What you will learn Organs and Systems The digestive system I have a heart Lung Healthy eating Why we need vitamin and minerals Fit for life Smoking can kill you Keeping clean Teeth for life time 71 Humans 8a Organs and Systems The human body is made up of millions of cells. Groups of similar cells form tissues. An organ is formed from several different types of tissues. It carries out one particular job. When you are fit and healthy all the organ systems of your body work well together. 1. Brain Controls the movement and is the centre of thinking, memories and emotions. Part of the nervous system. 1 2. Lungs Supply the body with oxygen. Part of the breathing system. 4 3. Kidneys Keep the blood clean. Part of the excretory system. 4 5 2 6 3 7 4. Bones Give support and protection and allow movement. Part of the skeletal system. 4 5. Heart Pumps blood round the body. Part of the circulatory system. 6. Stomach Stores and mixes food. Part of the digestive system. 7. Sex organs Produce sex cells. Part of the reproductive system. 72 Do you Know? There are 206 bones in your skeleton. Posture How can you take care of your body so that the systems work well together? Good Posture is important. It is wise to take preventive measures before some thing goes wrong. So we have to be careful about our body. For example, good posture when studying and sitting so that the body is not strained. Incorrect posture can lead to difficulties with digestion, muscles or the skeleton. standing sitting These figures show the correct way of standing, sitting and lifting objects. lifting objects ? 1 Copy the table below and fill in the gaps. System Organs Function Skeletal Bones, muscles Movement Respiratory Circulatory Digestive Excretory Nervous Reproductive 2 Study the pictures below. Each shows a health risk that some people will take from time to time. Copy the title of each picture. Write down the name of the body system or systems that could be affected. K Ideas !It is important to keep the body fit and healthy to keep the system working well together. !Incorrect posture can lead to difficulties with digestion, muscles or the skeleton. Wash your hands Don’t smoke Don’t slouch 73 Humans 8b The digestive machine CUTTING CHOPPING ACID TANK CRUSHING MACHINE FAT DIGESTER FOR CELL S THE TO Y O B D Our digestive system is like a factory conveyor belt. Food travels, along the gut, getting broken down at various points. Small useful molecules are sent to the cells of the body, and any food that is undigested is passed out at the other end. Into the mouth Your digestive system starts from your mouth. But even after you have swallowed the food, it is not really inside your body. The gut or the digestive system is a long tube about 8-9m long which runs from your mouth to anus. In your mouth food is broken down into smaller pieces with the help of teeth and tongue. Your mouth also produces saliva. This makes your food easier to be swallowed. It also starts the chemical breakdown of some of your food. Down the tube Once you have swallowed your food, it is moved steadily along your gut. Muscles squeeze to keep the food moving and to mix it to a paste. The muscles contract and relax in wave like action and this is called peristalsis. Do peristalsis you know? Finely ground food is digested more quickly than large lumps. ! Carbohydrates spend the shortest time in the stomach, fats spend the largest. ! 74 The gut The chewed food is swallowed and goes into the oesophagus. This is a muscular tube which can squeeze food down to the stomach in 7 seconds. mouth Your stomach is a muscular bag containing acidic juices. It stores food for about 3-4 hours mixing it up and breaking down protein. oesophagus (food tube) stomach liver It takes about 6 hours for food to travel along the 6m length of your small intestine. The final breakdown of the food takes place here. pancreas All your undigested food such as fibre collects in the large intestine. This is passed out through the anus. small intestine large intestine anus ? 1 Write these sentences in the correct order. a. b. c. d. e. f. Waste material passes out through the anus. Food enters the gut through the mouth where it is chopped into smaller pieces by the teeth. In the small intestine, digestion is completed and the digested food is absorbed into the blood. After swallowing, food is moved along the gut by peristalsis. It enters the stomach, which is a muscular bag of acidic juices for digesting protein. In the large intestine, water is removed from the undigested remains of the food. K Ideas !The digestive system is a muscular tube running through the body. !Food is moved through the gut by muscles squeezing in peristalsis. 75 Humans 8c I have a heart The human heart is made mainly of muscles. It weighs about 375g and is about the size of a man’s fist. It is a muscle, the most active part in the body but it is not solid muscle. The heart is hollow inside. The space inside the heart is divided into two by a thick wall of muscle. When the heart is pumping, the two sides work together. Blood flows into each side, then the heart muscles contract, squeezing the blood out. It pumps blood to your lungs to pick up oxygen and get rid of carbon dioxide. It also pumps blood around your body, supplying the needs of all your cells and carrying away poisonous wastes. A heart beat pumps it out at high pressure through the arteries. Your heart beats about 70 times each minute through out your life. heart The heart pumps your blood around a system of tubes called blood vessels. Some blood vessels carry oxygen rich blood away from your heart to the body. These are called arteries. Other blood vessels bring blood loaded with carbon dioxide back to the heart. These are called veins. Do you know? Your heart beats roughly 160,000 times everyday. ! In a life time the heart will pump 300 million litres of blood. ! 76 Changing Circulation Your heart does not always beat at the same rate. Your heart rate depends on what you are doing, and change many times a day. This graph shows the kind of changes which could well take place in it. 140 120 Your heart rate(number of beats in 1 minute) You step in front of a car. It hoots at you. 100 Your alarm goes off 80 60 7am 8am 9am 10am 11am 12noon 1pm 40 sleeping eating breakfast walking to school writing dhivehi experiment in science PE doing maths running home Heart Problems A heart attack occurs when blood vessels to the heart wall are blocked and the heart muscle is starved of food and oxygen. You can look after your heart by: ! ! ! ! ? Doing regular exercise Eating a balanced diet, without too much fat Controlling your weight Not smoking 1 What is the job of a. b. heart? the blood? 2 Arteries and veins do different jobs. What are they? 3 Answer the questions using the above graph. a. b. c. What is your normal heart rate (roughly)? What makes your heart rate go up? When is your heart rate i. ii. lowest? highest? Why? K Ideas ! The heart pumps blood around a system of tubes called blood vessels. ! The two main types of blood vessels are arteries and veins. !Arteries carries oxygenated blood and vein carry deoxygenated blood. 77 Humans Lung 8d You breathe air into your lungs and take in oxygen. When you breathe out, you are getting rid of carbon dioxide and waste. If you hold your ribs as you breathe in you can feel your lungs filling with air. The lungs pass oxygen from the air into the blood supply. Oxygen is then delivered to all your cells to keep them alive. Healthy lungs are good at taking oxygen out of the air. Unhealthy lungs are not. How many times do you breathe in and out each minute? The Respiratory System Your lungs are protected inside your rib cage. The lungs are joined to your nose and mouth by tubes. The lungs and these tubes are known as the respiratory system. nose windpipe (trachea) mouth voicebox (larynx) You usually breathe air in through your nose. Inside of your nose is warm, wet and hairy. The air coming in gets warm and moist. It is cleaned as dust is trapped in the hairs. So it is safer to breathe in through your nose than through your mouth! bronchi lungs Do ribs you know? High up in the mountain the air has less oxygen. ! People who live high up have very big lungs. ! diaphragm 78 Inside the lungs How do you think that your lungs would be, like two pink balloons or like a pair of pink sponges? You need to get as much oxygen out of the air as possible. Why do you think sponges might be better for this than balloons? Air sacs in the lungs tiny blood vessel very thin wall (only one cell thick) oxygen goes into blood air in air out carbon dioxide comes out of blood thin layer of water Each of your lungs is made up of millions of tiny air sacs called alveoli. These air sacs make the lungs look like sponges. The alveoli are surrounded by several tiny blood vessels. The alveoli have very thin walls so that the distance between the air and the blood is very small. Oxygen goes from the lungs into the blood and carbon dioxide goes from the blood into the lungs to be breathed out. This gas exchange takes place every time you breathe. Imagine how fast it happens! You never even notice this exchange taking place. air sac What a lot of lung Gas exchange happens so fast because the alveoli in the lungs give the lungs a very large surface area. In one lung we have about 300 million alveoli. If all the alveoli in both the lungs could be spread out flat, they would cover a tennis court. ? 1 Copy and complete the following sentences. Use the correct words from below. air alveoli surface area vessels oxygen blood The lungs are made of tiny air sacs called ________. The air sacs have thin moist walls and a large________. They are close to tiny blood_______. K Ideas !The lungs are made up of tiny air sacs called alveoli. !Gas exchange take place in the alveoli. !Alveoli give the lungs a big surface area so that gas exchange is faster. 2 Why do people who, live high up have bigger lungs than the people who live at sea level? 79 Humans 8e Healthy Eating What would you like for dinner? Some people eat such a varied diet that it usually includes everything that is needed to keep the body healthy, without having them to think about it. Why do you need food and what food do you need? The food you eat supplies the raw materials for building the body and for making it work properly. These raw materials are Proteins - for growth and repair Fats - provides energy and keep the body warm Carbohydrates - which gives energy But a healthy diet has to include other ingredients as well. Vitamins and minerals are essential for health. The final ingredient of a healthy diet is roughage (vegetable fibre). Not more not less Fat has more energy than carbohydrate. You need some fat to keep healthy. If you eat more food than you need for living and growing, the extra becomes a layer of fat. This acts as an energy store, but too much fat is very unhealthy. Too much fat can make you overweight and give you heart problems. If you do not eat enough, you get very thin and catch diseases easily. 80 Do you know? There is as much protein in peanuts as in meat. Soya beans contain more protein than either. ! There is more water in an apple than in milk. ! Balanced Diet You need all the food substances in the right amounts. When a diet has the right things in the right amounts, it is called a balanced diet. A simple rule is to eat something everyday from each of the four food groups shown below. Malnutrition is caused by having a diet that is not balanced. A Regular Habit The food we can not use should be pushed out of our bodies as feaces within 24 hours. If our food does not move through the body quickly the result is constipation. So it is important to include foods which contain fibre. Fibre provides bulk during digestion and helps to prevent constipation. Whole meal foods, prunes, apricots, peas and beans are all good sources of fibre. food rich in fats food rich in carbohydrates food rich in proteins food rich in vitamins and minerals K ? Ideas !A healthy diet should 1 Fill in the blanks We must eat the right amount of ______, ______, ______, and __________ for a healthier diet. If we eat too much we become ________ and give us _______. 2 Explain each of these facts. a. b. Children need more proteins in their diet than adults. When people try to lose weight, they need to cut down the amount of fatty food they eat. contain foods which contain carbohydrates, proteins, fats, vitamins, minerals and lots of fibre. !These must be eaten in the right amounts for a healthy balanced diet. !Fibre is important to include in your diets to prevent constipation. 81 Humans 8f Why we need vitamins and minerals Vitamins and minerals are necessary for life (in fact, vita means life). Humans need only tiny amounts of each vitamin, but if one of them is missing, a deficiency disease occurs. Vitamins As you grow up, your bones get bigger and longer. You need vitamin D to make sure your bones and teeth grow strong. If you don’t get enough vitamin D, your bones are soft and will not hold your weight without bending. This condition is called rickets. Cod liver oil is full of vitamin D and your skin can make vitamin D using sunlight. You need vitamin C for healthy gums and skin. In the olden days sailors didn’t get fresh fruit on long voyages, and many died of scurvy, the disease caused by lack of vitamin C. Vitamin C is found in oranges and lemons and lots of green vegetables. Vitamin A is found in liver, carrot and milk. You need vitamin A for good eyesight. If you do not take in food that contains vitamin A, you get problems in seeing at night. You get night blindness. 82 Do you know? Most vitamins are now made by the chemical not extracted from living things. ! There are some vitamins which can do you harm if you eat too much of them. ! Minerals A healthy diet also contains minerals. Small amounts of many different minerals or chemical elements are essential for life. We need the mineral, calcium to make our bones hard and strong. We get lots of calcium when we drink milk or eat dairy products. We need the mineral, iron for our blood to carry oxygen properly. Without it we feel tired and weak. We get iron when we eat red meat, liver, eggs. The mineral phosphorous is also important for teeth and bones. This is also important in the cells of our bodies. Phosphorous is present in most foods we eat. Iodine is important to keep up the activity of cells. If there is a lack of iodine in the food we take, the thyroid gland in the throat may swell into a goitre. We get iodine when we eat sea foods or it is present in iodised table salt. Our bodies also need sodium, but many people eat too much sodium (as sodium chloride or salt) rather than too little. On average, we use two teaspoonful (10g) of table salt a day. In fact we need only one gram of salt each day, not the 10g most of us eat. Too much salt can lead to high blood pressure. People with high blood pressure are likely to have heart diseases and strokes. ? 1 Copy and complete the following sentences. Use the correct words from below. calcium blood iron iodine vitamins minerals Human need the right amount of ________ and _________ to keep the body healthy. We need the mineral _______ for our body to carry oxygen properly. Milk is good source of __________ for healthy bones and teeth. K Ideas !Vitamins and minerals are essential to keep us healhy. !They protect our bodies from various diseases. 83 Humans Fit for life 8g We often hear people talking about getting fit and keeping fit. We are encouraged to get fit and stay fit. But what do we mean by fitness? “Fitness is having suppleness, strength and stamina” Suppleness - Being able to bend, stretch, twist and turn through a full range of movement. Strength - Being able to exert force for pushing, pulling and lifting. Stamina - Being able to keep going, when running or walking briskly, without geting tired and puffed very quickly. You could even describe fitness as the ability of all organs of the body to function effectively and efficiently. Fuelling Fitness You can improve the three kinds of fitness mentioned above by making sure you have varied, regular exercise. When you exercise, it is not only about the muscles and moving your skeleton, most of your body gets involved. Number of heart beats per minute (heart rate) How exercise affects the heart rate 150 100 after 2 minutes of hard exercise 50 at rest 0 84 average person at rest after 2 minutes of hard exercise Do you Know? Two weeks exercise can make a weak muscle twice as strong. fit person Fitness tests When you exercise your heart beat increases. If you are unfit it increases much more than if you are fit. It will also return to normal more slowly if you are unfit. When you first start exercising your heart pounds with the effort, but when you start exercising regularly, the heart gets stronger. It beats more strong and efficiently as you get fit. It can supply all the food and oxygen you need without pumping too hard and too fast. You will have less chance of getting heart diseases. More oxygen When you exercise you need more oxygen, so you breathe more. If you are not very fit, you soon get puffed because you can not get enough air. But as you practice and get fitter, your lungs get bigger. You breathe more deeply, and gives you a much better oxygen supply. You can exercise more without getting so puffed. ? K 1 When you run to catch up with your friends, what happens to your a. b. breathing your heart 2 A fit and an unfit person are sitting reading quietly together. The fit person’s heart beats more slowly than the unfit person’s heart. Also, the fit person breathes fewer times each minute. Why is this? 3 Design a poster to show Do’s and Don’ts for Ideas !Fitness is having suppleness, strength and stamina and ability of all organs of the body to function effectively and efficently. !Fitness can be improved by varied regular exercise. !Exercise makes your heart and lungs get stronger. keeping fit. 85 Humans 8h Smoking can kill you Tobacco smoke contains chemicals that can damage your lungs. Tar is a dark brown, sticky substance, which collects in the lungs as the tobacco smoke cools. It goes into the alveoli. As tar builds up, the alveoli are damaged. The thin walls of alveoli get so thicker that it becomes difficult to exchange gases properly. It also contains substances which cause cancer. Lung cancer is a very dangerous type of cancer. It can grow without causing problems until it is too late to cure. Nicotine is a poison. It makes the arteries narrower. Then your heart has to pump harder to push blood along. Smokers also get coughs, shortness of breath and lots of phlegm. Not only it damage the lungs, smoking is very bad for the heart too. Do you know? Cigarrette smoke in the air contains higher concentrations of harmful chemicals about twice as much nicotine, three times more tar and five times more carbon dioxide. ! 86 Damage the cleaning system Inside the tubes of your respiratory system has hair like structures called cilia. The whip like movements of these cilia move dirt and mucus out of the tubes, keeping your lungs pink and clean. But tobacco smoke stops the cilia working. Tar and also other mucus get into the lungs. It really is no wonder smokers cough. Passive smoking You can damage your lungs by breathing in smoke from other people’s cigarettes. This is called passive smoking. So you have to be away from smoky places to prevent the damage. K Ideas !Cigarrette smoke ? contains tar which can cause lung cancer. 1 Why does smoking make gas exchange in the lungs more difficult. 2 Write a paragrapgh to explain why smoking is not a good idea. 3 Make a poster to warn people how dangerous !It also makes the alveoli thick and exchanges of gases become difficult. !It increases the risk of many diseases. smoking can be. 87 Humans 8i keeping clean Negletting your body is not only unattractive, its unhealthy too! Look at the pictures of the boys. Now write down two things that are different about them. What happened to make the two faces so different? Could it be anything to do with hygiene? Write down two things that you should do to keep your skin and teeth healthy. The skin is the largest organ of the human body. It covers a person completely from head to toe. Skin is water proof and tough enough to protect someone from germs and dirt. Skin contains nerves which send messages to the brain about the texture or surface of things that we touch. The skin gives you identity by defining the colour and shape a person sees in a mirror. Do you Know? Skin cells keep dividing and making new cells through the year. 88 Skin care When you are a teenager you may sweat more and your skin may become very greasy. This is normal part of development and there is nothing wrong with you. But you do need to be more careful about washing your face, hands and body to remove the dirt and grease. If you didn’t the sebaceous glands and the sweat glands and pores can get blocked and they become infected by germs. How does the soap help to keep you clean? Grease can not dissolve in water but it can dissolve in the chemicals that make soap. The soap can also mix with water. So when you wash, the soap and water remove the grease, dirt and the germs that are mixed in with them. K Ideas !The sebaceous glands, sweat glands and pores can get blocked if you are not careful about washing. ? !Soap and water is used 1 Make a poster to show that good hygiene is to remove the grease, dirt and germs. necessary to look attractive and be healthy. 89 Humans 8j Teeth for lifetime Some people crack nuts with their teeth and even use them to wrench the tops of bottles. Acrobats can even hang by their teeth. You are not recommended to do any of these if you want your teeth to last a life time. But this gives you some idea of how strong your teeth are. Tooth Decay Tooth decay starts when harmful bacteria in your mouth form a sticky film that covers the teeth. This film is called plaque. Sugar in your food mixes with the plaque to make an acid. The acid starts to eat into the enamel that covers the outside of the tooth and so the tooth starts to decay. Do you know? The enamel that covers the outside of teeth is the hardest substance in the body, but it is affected by acid. ! 90 Tooth care The first and most effective step is to brush your teeth regularly, last thing at night and after every meal. This reduces the plaque and so prevents the formation of the acids which causes teeth decay. The dangers of a sweet tooth The more sugar and sugary foods you eat, greater is the risk of tooth decay. If you cannot brush your teeth easily after a meal, eat a piece of cheese. Cheese neutralises the acid formed. cheese K Ideas !Plaque mix with sugar to make an acid. This acid eats away the enamel. ? 1 What is a plaque, and how does it form? 2 Why does plaque cause problems for your teeth? 3 Make a poster with some rules to care for your !Most effective way to prevent tooth decay is to brush teeth regularly and reduce the sugary food we eat. teeth. 91 Humans MOHAMMAD IBN ZAKARIY A AL-RAZI AKARIYA (864-930C.E.) Abu Bakr Mohammad Ibn Zakariya al-Razi was born at Ray, Iran. Initially, he was interested in music but later on he learnt medicine, mathematics, astronomy, chemistry and philosophy. In medicine, his contribution was so significant that it can only be compared to that of Ibn Sina. His al-Judari wal Hasabah was the first treatise on smallpox and chicken-pox, and is largely based on Razi’s original contribution. He became the first to draw clear comparisons between smallpox and chicken-pox. Al-Hawi was the largest medical encyclopaedia composed by then. It contained on each medical subject all important information that was available from Greek and Arab sources, and this was concluded by him by giving his own remarks based on his experience and views. A special feature of his medical system was that he greatly favoured cure through correct and regulated food. This was combined with his emphasis on the influence of psychological factors on health. He also tried proposed remedies first on animals in order to evaluate in their effects and side effects. He was also an expert surgeon and was the first to use opium for anaesthesia. 92