tag:blogger.com,1999:blog-69778988481372949132023-11-15T23:52:20.424+08:00HUMAN BODYInformation about human body systemUnknownnoreply@blogger.comBlogger31125tag:blogger.com,1999:blog-6977898848137294913.post-37999718662384263742008-01-05T18:41:00.000+08:002008-01-05T19:00:15.137+08:00<strong><span style="font-size:100%;">Reflexes</span></strong><br /><span style="font-size:100%;">If you touch something very hot, your hands pulls away almost instantly, without waiting for your brain to tell it to. This is an example of a reflex - a rapid reaction that helps to protect you from injury. A massage flashes from your hand to your spinal cord - the bundle of nerve cells running down your body. The message is then passed straight to motor nerves, which make your arm muscles contract.</span><br /><span style="font-size:100%;"></span><br /><span style="font-size:100%;">Reflex actions happen automatically, and often do not involve signals from the brain.</span><br /><span style="font-size:100%;"></span><br /><span style="font-size:100%;">Deliberate actions - such as picking a paper, are triggered by signals from the brain.</span><br /><span style="font-size:100%;"></span><br /><span style="font-size:100%;"><strong>Sensitive parts</strong> </span><br /><span style="font-size:100%;">All over your body, you have nerve ending that give you information about the things you touch. Instead of being spread out, they are concentrated in places where the sense of touch is most useful. The parts of the body that have the most nerve endings are drawn enlarged. The most sensitive parts are the mouth and fingertips, while the least sensitive are the backs of the arms and legs. You can prove this by closing your eyes, and asking a friend to touch your skin gently in sensitive areas with a pencil or paintbrush. </span><br /><span style="font-size:100%;"></span><br /><strong><span style="font-size:100%;">The gentle touch</span></strong><br /><span style="font-size:100%;">Extra sensitive hands and fingertips help us to adjust our grip when we pick things up.</span><br /><br /><span style="font-family:trebuchet ms;font-size:85%;">Tag :<a href="http://technorati.com/tags/reflexes" rel="”tag”">reflexes</a> </span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-16688305832314167432007-12-26T15:40:00.000+08:002007-12-26T15:59:38.517+08:00<strong><span style="font-family:trebuchet ms;">All in the mind</span></strong><br /><span style="font-family:trebuchet ms;">Your brain is divided into three main parts. Two of them called the brain stem and the cerebellum, control essential processes such as breathing, and keep all the parts of your body working together. The third part is much bigger, and allows you to sense things, think, and make your body move.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Brain functions </span></strong><br /><span style="font-family:trebuchet ms;">Seeing the world : Several areas of your brain are involved in interpreting signals from the optic nerves in your eyes.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Tuning in : The area that deals with interpreting sounds, called the auditory area, receives signals from nerves in your ears.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Fine control : Whenever you make complicated movements, for example when using a keyboard, the part called the <span class="blsp-spelling-error" id="SPELLING_ERROR_0">premotor</span> area helps to control your muscles.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Thinking and understanding : The front of the brain is where thinking takes place. The ability to think makes us aware that we exist. The two side work in slightly different ways. In most people, the "right side" deals with shapes and feelings.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Feeling your body : The area of the brain that receives signals from nerves in the skin is called the sensory area. It allows you to feel pressure, heat, cold and pain.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Making movement : The area of the brain that sends out signals telling muscles to contract when you decide to move is called the motor area.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Dealing with words : The speech area controls the muscles you use when you talk. A nearby part of the brain helps you to understand words when people speak to you.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Left side : The left side of the brain deals with logical matters, such as maths.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;font-size:85%;">Tag :<a href="http://technorati.com/tags/brain" rel="”tag”">brain functions</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-63713819631139680772007-12-14T22:18:00.000+08:002007-12-14T22:32:13.791+08:00<strong><span style="font-family:trebuchet ms;">How do we remember things?</span></strong><br /><span style="font-family:trebuchet ms;">Scientist are still not certain how the brain remembers things, but they have produced a likely explanation. They know that each cell in the brain is connected to thousands of other cells via connection points called synapses. They think that the brain stores new information by forming new sets of connections between cells, it is as if the cells in the brain are constantly being rewired. At first, information is stored in your short-term memory. The information is then transferred into your long-term memory, which can store it for days, months or even years. </span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Lost forever</span></strong><br /><span style="font-family:trebuchet ms;">Unlike other cells in your body, the cells in your brain cannot be replaced when they get worn out. As a result, the number of cells in your brain steadily decreases as you get older. </span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Tag :<a href="http://technorati.com/tags/memory" rel="”tag”">memory</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-39835793438677674152007-12-05T01:17:00.000+08:002007-12-05T01:28:44.935+08:00<strong><span style="font-family:trebuchet ms;">How do nerves work?</span></strong><br /><span style="font-family:trebuchet ms;">Most nerves cells have a long thread, called an axon, which works partly like a battery and partly like a wire. When the nerves is resting, the axon is charged with electricity, just like the terminals of a battery. When the nerves is triggered into action, the charge suddenly changes, creating a signal that flashed down the axon. The nerves that the signals pass along to tell muscles to contract are called 'motor nerves. The nerves that carry messages from sense organs to your brain are called 'sensory' nerves. Signals travel along nerves at about 360 km/h (225 mph), fast enough to travel from your brain to your toes in less than 1/50 of a second.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;font-size:85%;">Tag :<a href="http://technorati.com/tags/nerves" rel="”tag”">nerves work</a> </span><br /><span style="font-family:Trebuchet MS;"></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-13203686768106544722007-11-29T21:16:00.000+08:002007-11-29T21:24:39.599+08:00BRAIN AND NERVOUS SYSTEM<span style="font-family:trebuchet ms;">Every second, whether you are awake or fast asleep, your is busy processing information. It receives millions of signals from all parts of the body, and its sends out signals that control the way your body works. These signals travel along nerves, bundles of cells that conduct tiny bursts of electricity. The brain itself contain more than 1000 billion nerve cells, and when they are busy these cells generate enough electrical energy to power a <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">light bulb</span>.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Unlike other cells in your body, the cells in your brain cannot be replaced when they get worn out. As a result, the number of cells in your brain steadily decreases as you get older.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Tag :<a href="http://technorati.com/tags/brain" rel="”tag”">brain</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-78741996797873511002007-11-28T12:04:00.000+08:002007-11-28T12:23:30.071+08:00<strong><span style="font-family:trebuchet ms;">Sweat glands</span></strong><br /><span style="font-family:trebuchet ms;">Sweat is a watery fluid that helps to keep your cool. It is made by coiled glands that open onto the surface of your skin. The palms of your hands have more sweat glands than <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">anywhere</span> else, up to 500 per cm2 of skin (3250 per sq in).</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Fingerprints </span></strong><br /><p><span style="font-family:trebuchet ms;">Whenever you touch anything smooth, your fingers leave marks. These marks are called fingerprints. Fingerprints are made of sweat and <span class="blsp-spelling-corrected" id="SPELLING_ERROR_1">body</span> oils, and they are exact copies of the tiny ridges that cover your fingertips. Identical twins have matching fingerprints, but everybody else has their own unique pattern, which will resemble one of the basic patterns. Fingerprints are often used to identify people <span class="blsp-spelling-corrected" id="SPELLING_ERROR_2">present</span> at the scene of a crime. To find fingerprints, police scientists dusts the objects at a crime scene with a fine powder. This sticks to the sweat and oil that the fingers have left behind, making the marks show up. The police then see if the marks match <span class="blsp-spelling-error" id="SPELLING_ERROR_3">up</span> with the fingerprints of any of their suspects. There are four kinds of fingerprints :</span></p><ul><li><span style="font-family:trebuchet ms;">Arch</span></li><li><span style="font-family:trebuchet ms;">Loop</span></li><li><span style="font-family:trebuchet ms;">Whorl</span></li><li><span style="font-family:trebuchet ms;">Composite</span></li></ul><p><span style="font-family:trebuchet ms;">Tag :<a href="http://technorati.com/tags/Sweat" rel="”tag”">Sweat glands</a></span></p><p><span style="font-family:trebuchet ms;">Tag :<a href="http://technorati.com/tags/fingerprints" rel="”tag”">fingerprints</a></span></p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-73759854645785474902007-11-27T21:16:00.000+08:002007-11-27T21:27:15.411+08:00<strong><span style="font-family:trebuchet ms;">Hair</span></strong><br /><span style="font-family:trebuchet ms;">Hair protects your head and eyes from the sun. On other parts of your body, it helps you feel things brushing <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">against</span> your skin. And it helps to keep you warm. Most of a hair is made of dead cells.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Can hair really stand on end?</span></strong><br /><span style="font-family:trebuchet ms;">If you are cold or frightened, your hair may feel as if it is standing on end. A tiny muscle pulls on the root of each hair, levering it int a more upright position. As each hair moves, it pushed <span class="blsp-spelling-corrected" id="SPELLING_ERROR_1">against</span> the skin, making a '<span class="blsp-spelling-error" id="SPELLING_ERROR_2">goosebump</span>'. Long ago humans had lots of body hair, and warm air would have been trapped in the little pits formed by goosebumps.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Tag :<a href="http://technorati.com/tags/hair" rel="”tag”">hair</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-64563559929950439432007-11-27T13:23:00.000+08:002007-11-27T13:33:31.368+08:00<strong><span style="font-family:trebuchet ms;">Skin ridges</span></strong><br /><span style="font-family:trebuchet ms;">These ridges are found only on fingers and toes, and on the palms of your hands and soles of your feet. They help to give you a good grip. The skin underneath them is extra thick for added protection.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Fingernails</span></strong><br /><span style="font-family:trebuchet ms;">Nails protect your fingertips (and toenails your toes), and also help you to pick things up. They are made from keratin, the same substance that makes hair. On average, a fingernail grows at a rate of about 1 mm (1/32 in) per <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">week</span>, four times faster than a toenail.</span><br /><span style="font-family:Trebuchet MS;"></span><br /><span style="font-family:Trebuchet MS;">Tag :<a href="http://technorati.com/tags/skin" rel="”tag”">skin ridges</a></span><br /><span style="font-family:Trebuchet MS;">Tag :<a href="http://technorati.com/tags/fingernails" rel="”tag”">fingernails</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-61824290786137921072007-11-26T21:10:00.000+08:002007-11-26T21:20:40.688+08:00<strong><span style="font-family:trebuchet ms;">Why are people different colours?</span></strong><br /><span style="font-family:trebuchet ms;">Skin gets its colour from chemicals called pigments present in skin cells. One pigment, called melanin, makes skin brown or black. Another, called carotene, gives skin a yellow colour. Pigments help to protect skin <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">against</span> damage by strong sunshine. People with pale skin have very little pigment and may easily get sunburned. If your skin is like this, it is important to stay covered up in strong sunshine, or to use sunblock.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Some people have more of a particular skin pigment than others. Apart from this, <span class="blsp-spelling-error" id="SPELLING_ERROR_1">everyone's</span> skin is the same.</span><br /><span style="font-family:Trebuchet MS;"></span><br /><span style="font-family:Trebuchet MS;">Tag :<a href="http://technorati.com/tags/skin" rel="”tag”">skin colours</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-51983617643851098162007-11-26T11:16:00.000+08:002007-11-26T11:25:13.119+08:00<strong><span style="font-family:trebuchet ms;">What is skin made of?</span></strong><br /><span style="font-family:trebuchet ms;">Skin is made of cells arranged in three main layer. The deepest layer, called the dermis, contains living cells, blood vessels and nerve endings that sense pressure, heat, cold and pain. Above this is a thin layer, called the epidermis, that produces new cells all the time. The new cells die as they are slowly pushed towards the surface, where they from a protective outer layer. Then they fall away in small flakes.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;"><strong>Flaking away</strong> </span><br /><span style="font-family:trebuchet ms;">The surface of skin, magnified about 200 times, with flakes of dead cells forming.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Tag :<a href="http://technorati.com/tags/skin" rel="”tag”">skin made</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-87502130541734219692007-11-25T22:43:00.000+08:002007-11-25T23:00:46.624+08:00SKIN, HAIR AND NAILS<span style="font-family:trebuchet ms;">Skin grows in step with the rest of your body, and although it constantly wears away, it is also replacing itself all the time. Like hair and nails, skin helps to protect your body from the out side world. It can do this because its surface is made of dead cells. These are very tough, and they from a barrier that shields the living cells underneath. Like the surface of skin, most of each hair is also made of dead cells.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;"><strong>Under the surface</strong> </span><br /><span style="font-family:trebuchet ms;">Each part of your body has a different type of skin. For example, the skin on the back of your arm is covered with lots of hairs, although they may be too small for you to see. The skin on the palms of your hands and the inside of your fingers has no hair at all, but it does have lots of tiny ridges and invisible openings called sweat glands.</span><br /><span style="font-family:Trebuchet MS;"></span><br /><span style="font-family:trebuchet ms;">Tag :<a href=”http://technorati.com/tags/skin” rel=”tag”>skin</a></span><br /><span style="font-family:trebuchet ms;">Tag :<a href=”http://technorati.com/tags/hair” rel=”tag”>hair</a></span><br /><span style="font-family:trebuchet ms;">Tag :<a href=”http://technorati.com/tags/nails” rel=”tag”>nails</a></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-9280720420897876002007-11-25T15:19:00.000+08:002007-11-25T15:31:22.917+08:00<strong><span style="font-family:trebuchet ms;">Sneezes and hiccups</span></strong><br /><span style="font-family:trebuchet ms;">Breathing normally happens so smoothly that we hardly notice it. But sometimes it is interrupted by a <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">cough</span>, a sneeze, or by hiccups. Hiccups happen when your <span class="blsp-spelling-corrected" id="SPELLING_ERROR_1">diaphragm</span> contracts suddenly and air rushes into your lungs. Your vocal cords, membranes lying across your trachea <span class="blsp-spelling-corrected" id="SPELLING_ERROR_2">that</span> you use to talk, close, making a loud squeak. Coughs and sneezes clear out dust and other particles that get trapped in your airways and the lining of your nose. Colds cause coughs and sneezes for a few days, smoking can give people cough for years because some of the smoke gets stuck in the lungs.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;">Drops of moisture, dust and germs shoot into the air when you sneezes.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-62320233289098068162007-11-24T21:03:00.000+08:002007-11-24T21:19:04.913+08:00<strong><span style="font-family:trebuchet ms;">Why do you get out of breath? </span></strong><br /><span style="font-family:trebuchet ms;">The amount of oxygen you need depends on how hard your body is working. If you are resting, you need only a small amount. If you are running or playing badminton, you use up oxygen more quickly producing enough energy. An area in your brain automatically adjusts your breathing rate to make sure you get the oxygen you need, by breathing faster and more deeply. </span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Gasping for air</span></strong><br /><span style="font-family:trebuchet ms;">At rest, a 10-years-old takes in about 0.25 litre (15 cu in) <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">of</span> air with each breath. If you take deep breaths, you will take in seven times more air than this. If you work hard, you will force more air out of your lungs and take in ten time more air.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-792830397024813032007-11-24T07:05:00.000+08:002007-11-24T07:15:25.458+08:00<strong><span style="font-family:trebuchet ms;">Breathing in and breathing out</span></strong><br /><span style="font-family:trebuchet ms;">Lungs do not have any muscles, so they cannot move air on their own. Instead, muscles in the chest make the lungsexpand, or blow up like a balloon, as air is sucked in. Most of the work of breathing is done by muscles that raise the ribs, but if you breath out hard, for example when blowing a trumpet, you use muscles on the front of your belly as well. This pushes your insides upwards, squeezing the air out of your lungs more forcefully.</span><br /><span style="font-family:Trebuchet MS;"></span><br /><span style="font-family:Trebuchet MS;"><strong>Big breathers</strong></span><br /><span style="font-family:Trebuchet MS;">People take, on average, more than half a billion breaths during a lifetime. Each person's lungs move about 250 000 m3 (8 million cu ft) of air, a quantity that would fill the biggest airship ever built. <blockquote></blockquote></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-15334385695226852862007-11-23T23:05:00.000+08:002007-11-23T23:15:51.553+08:00<strong><span style="font-family:trebuchet ms;">How do lungs work?</span></strong><br /><span style="font-family:trebuchet ms;">When you breath in, air flows through the bronchi and <span class="blsp-spelling-error" id="SPELLING_ERROR_0">bronchioles</span> in your lungs, and comes to a halt in millions of air pockets, known as <span class="blsp-spelling-error" id="SPELLING_ERROR_1">alveoli</span>. These pockets are surrounded by blood vessels that are so tiny they can be seen only under a microscope. The blood vessels are so thin that gases can pass straight through them. As blood flows around the air pockets, oxygen passes into the blood, while carbon dioxide waste in the blood passes into the pockets to be breathed out.</span><br /><span style="font-family:Trebuchet MS;"></span><br /><span style="font-family:Trebuchet MS;"><strong>Inside a lung</strong></span><br /><span style="font-family:Trebuchet MS;">The trachea branches off to the right and left lung. Each lung is made up of a mass of subdividing airways.</span><br /><span style="font-family:Trebuchet MS;"></span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-28184630160817754222007-11-23T14:20:00.000+08:002007-11-23T14:41:35.492+08:00LUNGS AND BREATHING<span style="font-family:trebuchet ms;">Human need oxygen to survive. Each time you take a breath, air rushes into your lungs and oxygen passes from the air into your blood. To get enough oxygen into your body your lungs need a very large surface area in contact with the air. If your lungs could be unpacked and laid out flat, they could wrap up your body at least 25 times.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">What do lungs look like?</span></strong><br /><span style="font-family:trebuchet ms;">Lungs are like air-filled sponges. Air flows into the lungs through a tube called the windpipe. This tube divides into many smaller tubes called bronchi, and these subdivide again into even smaller tubes called bronchioles. Each bronchiole ends in a cluster of tiny air pockets called alveoli, which are buried deep inside the lungs. You can also find the diagram of lungs at </span><a href="http://www.mydr.com.au/"><span style="font-family:trebuchet ms;">www.mydr.com.au</span></a>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-31642200469913969342007-11-22T19:28:00.000+08:002007-11-22T19:36:29.629+08:00<strong><span style="font-family:trebuchet ms;">How does the heart work?</span></strong><br /><span style="font-family:trebuchet ms;">Your heart is made of muscle, and has two chambers, called the atrium and the ventricle, on each side. About 100 000 times a day, the heart fills with blood and then contracts to pump the blood out again. This contraction is called a heartbeat. Deoxygenated blood from your body flows into the right side of your body flows into the right side of your heart, and is pumped to the lungs, where it takes in oxygen. The oxygenated blood returns to the left side, which pumps the blood returns to the left side, which pumps the blood out through a large artery called the aorta and around your body. Each side of your heart has two valve. These are flaps that stop blood flowing backwards after each beat.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-4582585899209952782007-11-22T08:08:00.000+08:002007-11-22T08:16:48.656+08:00<strong><span style="font-family:trebuchet ms;">Why do scabs form?</span></strong><br /><span style="font-family:trebuchet ms;">If blood was like water, it would drain away through cuts and grazes. Instead, small leaks are quickly plugged, bringing bleeding to a halt. This happens because blood contains chemical called <span class="blsp-spelling-error" id="SPELLING_ERROR_0">fibrinogen</span>. When a blood vessel is cut, the <span class="blsp-spelling-error" id="SPELLING_ERROR_1">fibrinogen</span> turn into another chemical, called fibrin, which creates a maze of sticky strands. Blood cells get trapped in the strands, making a solid plug called a clot. Once a clot has formed, the skin underneath starts to heal. Eventually, the clot dries out to form a scab, which later falls off. By this time, the injury has been fully repaired.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-32074897992451422402007-11-21T15:05:00.000+08:002007-11-21T15:14:28.682+08:00<strong><span style="font-family:trebuchet ms;">Why is blood red?</span></strong><br /><span style="font-family:trebuchet ms;">Blood gets its colour from a red chemical called haemoglobin, which is stored in red blood cells. When blood flows through the lung, the haemoglobin collects oxygen and carries it to other parts of the body. Haemoglobin that is carrying oxygen is bright red, but it has released its oxygen into the body's cells as it flows past them, it becomes much darker. As a result, the blood flowing in your arteries is brighter red than the blood flowing in your veins.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-83818648536143212362007-11-21T08:21:00.000+08:002007-11-21T08:31:36.136+08:00<strong><span style="font-family:trebuchet ms;">Where does blood go?</span></strong><br /><span style="font-family:trebuchet ms;">Bloods travels around your body in a network of pipes called blood vessels. The blood vessels that carry blood away from the heart are called arteries, the one that carry it back again are called veins. Arteries and veins are connected to each other by more than 80 000 km (50 000 miles) of capillaries, tiny vessels much thinner than a hair. Arteries expand every time your heart beats. In places such as the wrist, this creates a<em> 'pulse'</em> you can feel.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">replacement service</span></strong><br /><span style="font-family:trebuchet ms;">A single drop of blood contains about 250 million red cells and over 300 000 white cells. Red cells wear out quickly, and every day the blood makes about 2.5 billion new ones to replace them.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-34497265333955151992007-11-20T15:09:00.000+08:002007-11-20T15:19:30.615+08:00<strong><span style="font-family:trebuchet ms;">What is blood made of?</span></strong><br /><span style="font-family:trebuchet ms;">Blood is a complicated mixture of liquids, chemicals and cells. If you could separate out the ingredients in a single drop of blood, you would find that just over half of it is made of liquid called plasma. Plasmas consists mainly of water, but it also contains many dissolved chemicals. One of these is glucose, the substance that your body uses to make energy. The rest of the drop of blood would consist of millions of cells so tiny that they can only be seen under a microscope. Most of these cells are the red blood cells, which carry oxygen. Scattered among them are transparent cells called white cells, which are involved in fighting disease. Red blood cells are shape like tiny coins. White blood cells are bigger, and many can move about by changing shape.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-70828982516236087102007-11-19T14:32:00.000+08:002007-11-19T14:44:18.564+08:00BLOOD AND CIRCULATION<span style="font-family:trebuchet ms;">Blood is pumped to every part of your body by your heart. In an adult, up to 5 litres (8 pints) hurtle through arteries and veins, completing a double loop around the body in less than one minute. During this endless high-speed journey, blood delivers oxygen, collects waste, and supplies the substance that all your body's cells need to survive. Blood also helps the body to <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">fight</span> diseases, and it spreads warmth from one part of the body to another.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-11693957451493157332007-11-18T23:14:00.000+08:002007-11-18T23:20:24.396+08:00<strong><span style="font-family:trebuchet ms;">Muscles ache</span></strong><br /><span style="font-family:trebuchet ms;">Muscle need energy to work. They get it by using oxygen to break down a chemical fuel called <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">glucose</span>, a form of sugar, which is delivered to them by the blood. If a muscle is working hard, it starts to run short of oxygen and it cannot break down <span class="blsp-spelling-corrected" id="SPELLING_ERROR_1">glucose</span> in the normal way. Instead, glucose is turned into lactic acid. <span class="blsp-spelling-error" id="SPELLING_ERROR_2">The</span> acid builds up inside the muscle and makes it ache. If the muscle is allowed to rest, the acid is broken down and the ache disappears.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-26560791817312541362007-11-17T22:26:00.000+08:002007-11-19T14:47:58.499+08:00<strong><span style="font-family:trebuchet ms;">Working together</span></strong><br /><span style="font-family:trebuchet ms;">When you make complicated movement, such as running and jumping, you use many different muscles at the same time. Leg muscles push you along, arm muscles help you to stay balanced, and muscles in your back hold your body upright. Continual repetition of a movement decelops your ability to make all these muscles work together.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:Trebuchet MS;">Making faces</span></strong><br /><span style="font-family:trebuchet ms;">You have more than 40 different muscles in your face. You use them all the time when you are awake, and sometimes when you are asleep. They help you to speak, eat, and blink, and they also enable you to alter your expression. For humans, facial expressions are very important, because they allow us to show oyher people how are we sleeping. Babies know how to smile and laugh, but we learn many other expressions as we grow up. Try making faces at a friend, and see how many different feelings you can communicate without using words.</span>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6977898848137294913.post-47030520759392885062007-11-17T15:13:00.000+08:002007-11-17T15:39:38.916+08:00<strong><span style="font-family:trebuchet ms;">Can we control all our muscles?</span></strong><br /><span style="font-family:trebuchet ms;">You can control nearly all of the skeletal muscles. the one attached to your bones. You can control some of the muscles that work other parts of your body, such as the one you use to swallow, and those you use to make faces. You also have muscles, such as those in your eyes and <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">digestive</span> system, <span class="blsp-spelling-error" id="SPELLING_ERROR_1">that</span> work without your telling them to. </span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Running</span></strong><br /><span style="font-family:trebuchet ms;">Each time you take a stride, powerful muscles in the back of your thighs and calves press your feet and toes againts the ground, levering your body forwards. Muscles on the front of your thighs lift your legs.</span><br /><span style="font-family:trebuchet ms;"></span><br /><span style="font-family:trebuchet ms;"><strong>Closing up</strong> </span><br /><span style="font-family:trebuchet ms;">When bright light shine in your eyes, muscles inside your eyes automatically make your pupils smaller to reduce the amount of light getting in.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">In the air</span></strong><br /><span style="font-family:trebuchet ms;">Muscles in your shoulder and upper arm ruse and bend your arms to help you stay balanced when your body is off the ground. Muscles in your thighs raise your legs and keep them bent.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Landing</span></strong><br /><span style="font-family:trebuchet ms;">Thigh muscles hold your legs steady, with knees and ankles bent, ready to take the force of the impact with the ground. At the same time, muscles on the front of your body tighten up, keeping your stomach and intestines in place as you suddenly come to a halt.</span><br /><span style="font-family:trebuchet ms;"></span><br /><strong><span style="font-family:trebuchet ms;">Tired out</span></strong><br /><span style="font-family:trebuchet ms;">Athletes push themselves very hard during competition and their leg muscles take time to stop aching.</span>Unknownnoreply@blogger.com0