Innholdsfortegnelse for You: Did you know? - The Human Body i You South Africa

DID you know that as you’re reading this it’s not just your eyes and brain that are busy? By the time you get to the end of this page, your heart will have beaten about 120 times, your kidneys will have cleaned the equivalent of a bucket of blood and your lungs would have taken in 10 litres of air. And while all this important stuff is happening, the 100 000-or-so hairs on your head will collectively growing approximately 2,5cm and you d over 30 000 skin cells. Every moment of the day, all of this is going on in the background without you having to think about body’s the wonder of the human and it’s exactly what we’re aiming to share with you in this magazine. From the top…

TOOTH enamel is the hardest part of your entire body, even harder than bone. And yet your teeth are the only part of the body that can’t repair themselves – that’s because enamel isn’t a living tissue. TOOTH STRUCTURE • The visible part of a tooth is the crown. It’s made of enamel, which is light yellow to grey-white. • Enamel protects the internal part of the tooth. • Just beneath the enamel is dentine, of which most of the tooth is composed. Dentine isn’t as hard as enamel but supports the enamel layer and helps with its development. • Dentine protects the part of the tooth known as the pulp. The blood vessels in the pulp feed the tooth and keep it alive and healthy. • The pulp extends…

CORE MUSCLES These are all the muscles in your upper body and pelvis. They form your body’s centre of gravity, stabilise your skeleton and enable your limbs to move. INNER CORE MUSCLES These deep-lying muscles in the upper body work together to keep the upper body, back and pelvis stable. They allow spinning motions such as the pirouette. OUTER CORE MUSCLES These are muscles that usually extend over more than one joint and are visible beneath the skin. They enable greater upper-body movement. BENEFITS OF STRONG MUSCLES • Improve coordination • Better posture • Balance and stability • Reduce danger of injury • Provide better control of performance • Improve endurance • Develop self-confidence HIP AND GLUTEAL MUSCLES In classical ballet the legs are continually swivelled outwards at the hip…

YOUR brain is a powerful and complex structure. It’s the body’s most important organ because it sends out messages (via neurons which are cells in the nervous system) that allow you to function. Your feet, for example, get the message to walk; your jaws get the message to chew and your lungs to breathe. Your brain also allows you to perform abstract actions such as thinking and remembering. YOUR BRAIN AND LANGUAGE There are two specific areas of the brain that make it possible for you to talk and write. 1 BROCA’S AREA This area helps you to talk. If it were injured, you’d understand language but wouldn’t be able to talk or pronounce words properly. 2 WERNICKE’S AREA This part of the brain helps you to understand spoken and…

HOW do our lungs know to keep breathing when we sleep? How does your hand know to pull back from a hot stove plate? How does your nose tell you there are biscuits baking in the oven? All these things are possible thanks to the body s nervous system. WHAT IS THE NERVOUS SYSTEM? The nervous system is a network of nerves that is continually sending signals throughout your body to enable you to do things. Billions of tiny cells (called neurons) in your brain and elsewhere are always passing signals along – almost like a game of “telephone” when you and your friends share a secret by whispering it to the person next to you. The nervous system consists of the central and the peripheral nervous systems. CENTRAL NERVOUS…

WHEN you breathe in, your lungs are able to provide an uninter-rupted flow of oxygen to the blood. And when you breathe out you are able to rid the body of carbon dioxide. Carbon dioxide (CO²) forms as the body’s trillions of cells convert food into energy for cellular activity. This gas is a waste product and if too much of it builds up in your bloodstream, you could suffocate. Luckily carbon dioxide dissolves very easily in the blood which means it can easily be transported to the lungs wher it is expelled from your bod when you breathe out. OXYGEN (O2) The oxygen in the air you breathe passes through the lungs and is carried by the red blood cells to your organs. CARBON DIOXIDE (CO2) After the oxygen…

OUCH! It’s not fun getting a vaccination as often it means having an injection but the alternative is a lot worse. Although many vaccination-preventable diseases such as tetanus and measles can be treated, people who catch them are often left with complications, and some even end up dying. Let’s look at the damage these diseases and infections can cause the body and how vaccines work to protect us from them. HOW IMMUNITY WORKS When you’re exposed to a disease, your immune system naturally produces antibodies to fight it. This means that when you’re exposed to the disease again, your body recognises it and knows what to do. The first time the body faces a disease, it takes a few days for it to produce the antibodies needed, but for certain…

INTERESTING FACT The ISO (International Standards Organisation) states that first-aid boxes should have a white cross on a green background. Only the Red Cross, an international humanitarian organisation that helps victims in regions affected by war or natural disasters, uses a red cross on a white background. The emblem is protected under international law. It identifies the Red Cross as a neutral organisation that cannot be targeted during armed conflict. It’s therefore illegal to use this symbol on first-aid products. IMPORTANT Check your first-aid kit regularly to make sure everything you need is there – you might have run out of a particular item. Also make sure the medicines haven’t expired. STERILE BANDAGES These are used to staunch bleeding, strap sprains, cover larger wounds to protect them from infection and…

BRAIN There are no pain receptors in the brain so the brain itself does not feel pain. Surgery can be done on the brain and the brain itself won’t feel a thing! HAIR You lose about 80 hairs a day. But don’t worry – you have about 100 000 up there! SWEAT A right-handed person sweats more under their left arm. The opposite applies if you’re left-handed. KIDNEYS If you took all the tubes inside your kidneys and placed them end to end, they’d stretch more than 80km. FINGERNAILS You’ll find more germs under your fingernails than on a toilet seat. EYEBROWS You can develop dandruff here. NOSE When you’re breathing, air goes into your body at a speed of 6,5km/h. If you’re smelling something, it goes in at 32km/h.…

THE SKULL • The only moveable bone in the skull is the lower jawbone (mandible), which allows you to speak and chew. • The skull isn’t just made of bone – it also includes cartilage (put your finger on the tip of your nose and wiggle it) and ligaments which allow you to open and close your mouth. • The base of your skull is full of tiny holes called foramina. These openings allow for the passage of the nerves and vessels that supply blood to various structures housed within the skull. FUN FACTS • The funny bone isn’t a bone but rather a nerve. It’s the part of the elbow over which the ulnar nerve passes. If you bump this spot it will send a painful zinging sensation down…

YOUR THREE MAIN MUSCLES ARE: HEART MUSCLE This is your most important muscle. It’s an involuntary muscle (it does its job automatically) and never stops working, pumping blood throughout your body every moment of the day. SMOOTH MUSCLES These are involuntary muscles that you can’t control such as the muscles in your stomach walls. SKELETAL MUSCLES There are more than 600 skeletal muscles in the body. They’re voluntary muscles, which means they work when you want them to. Examples are the muscles of your arms and legs, which contract and relax as you move. These muscles work in opposing groups: one contracts (becomes shorter and thicker) while the other relaxes (becomes longer and thinner). STRONGEST MUSCLE The strongest muscle in the body is the masseter (a jaw muscle on each…

THE COMPONENTS OF BLOOD FUNCTIONS OF BLOOD Blood is a special fluid with various purposes in the body: • It transports oxygen from the lungs to the tissues. • It carries nutrients to cells in the organs that need the B It moves carbon dioxide to the lungs from where it’s exhaled. • It helps your body fight germs and infections. • It has a messenger function, transporting chemicals around the body that tell cells what to do. • It regulates body temperature and keeps your body tissue healthy. • It removes waste from the cells. RED CORPUSCLES These cells look like flat, indented discs and make up 45% of blood’s volume. They contain the iron-rich protein haemoglobin, which gives blood its red colour when it receives oxygen in the…

MOST of us are completely unaware of our hearts faithfully beating away in our chests – until we get a big fright or have to run a long way. While you’re running, sitting at your desk at school or just sleeping, your heart is working hard to pump blood and keep you alive — it beats around 100 000 times a day. That thud-thud-thud in your chest is your heart valves opening and closing. DID YOU KNOW? Your hart can move five to seven litres of blood in a minute or 7 600 litres per day. YOUR PULSE Two of the places you can feel your pulse beat are above major arteries on the side of the neck and on the inner surface of the wrist closest to the thumb.…

The human respiratory system is comprised of the following parts: NASAL CAVITY Cartilage down the middle of the nose divides it into two nasal cavities which help purify and warm air when we inhale it. NOSTRIL The entrance to the nasal cavity is filled with hairs that catch impurities. LARYNX (VOICE BOX) This has folds called vocal cords. Sounds are formed here when air causes the half-closed vocal cords to vibrate. WINDPIPE (TRACHEA) Air moves to and from the lungs in this tube. Cartilage keeps the windpipe firm and open. EPIGLOTTIS This flap at the back of the tongue blocks the windpipe, preventing food from getting into your lungs when you swallow. THROAT Where the mouth and the pharynx (tube behind the nose) meet. BRONCHUS One of many air passages…

ALTHOUGH the liver is one of he most important organs in our body, we're usually completely unaware of it unless something goes wrong. Unlike our stomach which growls hen we re heart that when we're hungry heart that starts beating willy when we're scared, the liver mostly does its important jobs quietly in the background. It processes basically everything you eat, drink, breath in and rub your skin. HUMAN LIVER ANATOMY GALL BLADDER The gall bladder sits directly under the liver. Its role is to store the bile produced by the liver. COMMON BILE DUCT The common bile duct carries bile from the liver and gallbladder through the pancreas and into the small intestine. PORTAL VEIN The portal vein transports blood from the intestines, spleen and pancreas that the liver…

WHAT BRINGS ON TEARS? 1. If you’re sad, that feeling registers in the part of your brain called the cerebrum. 2. The cerebrum sends signals o your endocrine system ( system responsible for your body secreting substances). 3. The endocrine system secretes chemical substances called hormones to the eye area. 4. These hormones cause the tear glands to form tears in response to your emotion. The gland produces many tears at once, almost like a fountain. WHY CRYING IS GOOD FOR YOU • Research has found that emotional tears, unlike other tears, contain a natural pain reliever that soothes both emotional and physical pain. • Experts also found emotional tears contain high levels of stress hormones, so crying helps your body get rid of these hormones, thereby relieving stress. •…

HOW YOU TASTE If you look at the tongue’s surface, you’ll see tiny bumps. These are our taste buds or papillae. The taste pores inside the papillae are the actual tasting organs. The substances in the food we eat stimulate these pores. Nerves inside the pores transmit signals to the brain, which are transformed into our perception of taste. That’s how you know what you’re eating. IDENTIFYING FLAVOURS Most taste buds are on the tongue’s surface, but there are also taste buds beneath the tongue and all over the mouth. Different taste buds allow us to taste different flavours – salt, sweet, bitter and sour. Some experts believe there’s a fifth taste: umami. It’s a Japanese word referring to a pleasant, salty flavour. Mushrooms are an example of umami. Though…

ALLERGIES are abnormal reactions by our immune system to things that are often harmless, like dust or pollen. When you’re allergic to something, your immune system mistakenly “thinks” the substance is dangerous. It then fights back, causing unpleasant symptoms such as rashes and sneezing. COMMON ALLERGIES RESPIRATORY AND EYES • Seasonal allergies • Pollen allergy • Mould allergy • Dust allergy • Dog allergy • Cat allergy Hay fever and asthma are common reactions to respiratory allergens. FOOD • Milk/dairy allergies • Egg allergy • Wheat allergy • Nut allergy • Fish allergy • Shellfish allergy • Soy allergy SKIN • Allergies to certain plants • Nickel allergy • Sun allergy • Allergies to insect stings • Allergies to cosmetics Several allergies can cause skin symptoms such as eczema or…

SOME bacteria are found on the surface of the skin and in the mouth and nose but most live in your intestines. Gut bacteria help our bodies to digest and absorb nutrients, supply vitamins, rally against intruders such as the flu virus, regulate our metabolism and boost our immune system. HEALTHY INTESTINAL BACTERIA There are about 5 600 bacterial species in our digestive system. Bacteria feed off the food passing through us but also play an important role in improving our digestion, metabolism and immune responses, and preventing bad bacteria from gaining a foothold. ACID AND ENZYMES The oesophagus (food pipe), stomach and first section of the small intestine are mostly bacteria-free. Bacteria avoid strong stomach acid and high levels of digestive enzymes. ANATOMY OF A BACTERIAL CELL Some bacteria…

HOW MUCH DO YOU KNOW? 1 How many bone are there in total both your feet? • A 6• B 26• C 52 2 Which is the biggest bone in the human body? • A The breastbone• B The shoulderblade• C The thighbone (femur) 3 To avoid tooth decay, what SHOULDN’T you do? • A Brush your teeth using a fluoride toothpaste• B Eat sweets and drink sugary drinks• C Floss regularly 4 How many canine teeth do adults have? • A 4• B 2• C 8 5 Where will you find the cornea? • A In your ear• B In your eye• C In your nose 6 Which ingredient of blood helps it to clot when you have a wound? • A Blood platelets• B Red corpuscles• C White…

WHY YOU NEED SO MANY BONES Support act: The human skeleton consists of more than 200 bones and its main purpose is to give the body shape and support. It holds the body upright and steady and shields your organs. Movement: The skeleton isn't an immovable, rigid structure. Thanks to joints it can perform many movements. Joints are points where two or more bones meet, and together with muscles (see page 16) they make movement possible. Joints are classified according to the type of movement they allow. TYPES OF JOINTS • Plane joint (or arthrodial joint): These are in parts of the body such as your wrist and ankle and allow only a slight, gliding movement. • Ball-and-socket joint: Found in the shoulders and hips, these allow a lot of…

TYPES OF TEETH • Humans have two sets of teeth: 20 primary teeth, also called baby or milk teeth, and 32 permanent or adult teeth. • Adult teeth develop between ages six and 12, replacing baby teeth, which fall out. • Children have eight molars, adults have 12. Grown-ups also have eight premolars, which kids don’t have. • Adults have four types of teeth. Incisors are the eight teeth at the front of the mouth. You use them to takes bites out of your food. Canines are your four sharpest teeth and are used for tearing food. The eight premolars are used for chewing and grinding food, while the 12 molars, which are similar to the premolars but bigger, also grind and chew. ADULT TOP TEETH (SIDE VIEW AND FROM…

DID YOU KNOW? An adult heart valve is just slightly bigger than a R5 coin. THE HUMAN HEART AT A GLANCE The heart of a human foetus starts beating 21 or 22 days after conception. It’s located in your chest cavity and is protected by the ribcage. Cardiology comes from the Greek kardia [heart] and logos [study] and is the science of the human heart. A healthy adult’s resting heart beats on average 60-100 times a minute. The heart is a muscle consisting of four chambers (the atriums and ventricles) and four valves. A heart is about the size of a fist for a child and two fists for an adult. Adults have about five litres of blood. A healthy heart keeps the blood in circulation, pumping it through nearly…

MOST people have two kidneys. These are reddish bean-shaped organs located in the lower back, one on each side of the spine. A kidney is about the size of an adult’s fist. Kidneys are part of the urinary tract. It’s where our bodies produce urine. ADRENAL GLAND This is a small gland that makes stress hormones, including adrenaline. HILUM The port of entry and exit of the renal arteries and veins. The renal pelvis and ureter also pass through here. RENAL ARTERY Transports blood with waste to the kidneys where it’s filtered. RENAL VEIN Transports the filtered blood from the kidneys back to the heart. RENAL PELVIS A hollow section where the urine collects and is funnelled into the ureter, the tube that connects the kidneys to the bladder. Each…

VIRAL INFECTION WHAT IS A VIRUS? It’s a tiny infectious agent that can only multiply itself inside a living host. Viruses enter the body when you breathe or through tears in the skin, or if you’ve swallowed contaminated food or liquids. They can cause several illnesses. SYMPTOMS OF VIRAL INFECTION HOW A VIRUS ATTACKS 1 The virus invades the body, in this case through the respiratory tract. 2 The virus begins to multiply. The respiratory tissue becomes infected. 3 Once the virus is in the respiratory system it invades the bloodstream. You then experience the first symptoms of flu. INFLUENZA OR FLU WHAT IS IT? It’s a respiratory (breathing) illness caused by the influenza virus. It’s not the same as a cold, though people often confuse the two because the…

EFFECTS OF LAUGHTER ON YOUR BODY LESSENS PAIN Laughing can turn you into a kind of superhero – it allows the body to block some pain. Natural painkillers called endorphins are released when you laugh. This also happens when you exercise. LOWERS BLOOD PRESSURE Laughing has been found to promote blood vessel relaxation, making for a healthier blood pressure reading. BOOSTS YOUR IMMUNE SYSTEM Stress is bad for your immune system (which helps to protect the body from germs) but positive activities such as laughter can strengthen it. AIDS WEIGHT LOSS Good news for those who want to shed excess weight – laughing can burn 20% more kilojoules than having a straight face. HELPS YOU STRESS LESS It helps to stimulate circulation and causes your muscles to relax in the…

Best case, the nasty bacteria won’t be able to survive your stomach acid and will die. Worst case, the contaminated food can produce toxins that irritate the stomach. If the bacteria manage to get past your stomach’s quality control system, they’ll pass into your small intestine and multiply. The bacteria multiply, releasing toxins that damage the walls of the small intestine. The area becomes inflamed and red. Your body responds to this attack by sending more quality-control troops – the antibodies – to the affected area. When you eat food that’s past its expiry date, there’s a chance you’ll also be ingesting nasty bacteria. Usually your bowels get seven litres of fluid every day, whether it be from mucus, saliva or stomach juices. When you have eaten something bad, your…

HOW DO SPOTS FORM? • Your skin has thousands of tiny pores and hair follicles containing fine hairs. Inside these little holes are oil glands that produce sebum, a special oil that keeps the hairs and skin soft and moist. • As your body changes you secrete hormones that tell the oil glands to produce more sebum. The glands go into overdrive and there’s too much oil mixing with dead skin, which then blocks the pores. • When bacteria enter the pores the blockage becomes a pimple that swells and turns red. VARIOUS KINDS OF SPOTS WHITEHEADS • An oil clot partially blocks a pore and the white pus protrudes over the top. Whiteheads aren’t red or swollen. BLACKHEADS • If the skin around a sebum and dead skin blockage…