Category Zoology

Why do I need minerals and vitamins?

                      You only need small amounts of these substances, but they are important in many of the processes that keep the body healthy. If you eat a healthy variety of foods you will be taking in plenty of vitamins and minerals. This is called a balanced diet. If you eat lots of ‘junk food’ this can mean that you are not taking in enough vitamins. You may need to eat more fresh fruit and vegetables.

Why should I eat fibre?

                    Fibre is the part of vegetable food that your body cannot digest. It provides the bulk in your diet. Fibre, or roughage, helps food to pass easily through the digestive system. It also helps to keep the system healthy and to prevent some serious diseases.

How much should I eat?

                  The amount of food you need each day depends on your age, size, sex and the amount of exercise you take. Older people need less food because they have stopped growing. A teenager who plays a lot of vigorous sport will need extra food to provide enough energy. Babies also need lots of energy to help them grow rapidly.

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Why do I need food?

                   Your body is built and maintained by substances that you obtain from your food. These substances are broken down and absorbed into the body during the process of digestion. They are then rebuilt into useful body-building materials.

Which foods give me energy?

                             Carbohydrates are substances that the body breaks down to produce energy. Starchy foods such as bread, potatoes and sugars contain carbohydrates. The body also uses some types of fat to provide energy.

Why is protein important?

                  Protein is an essential body-building substance that you obtain from meat, cheese, eggs, fish and several vegetable sources. Proteins are broken down in the body into amino acids that can be easily absorbed. Later, these amino acids are reassembled into useful proteins. A large part of the protein you eat is converted into muscle tissue.

What keeps the heart beating?

                Your heart is a muscular pump that never stops beating. It has its own timing device that produces tiny electrical signals. These signals cause the heart muscle to contract rhythmically. This mechanism allows a heart to be transplanted from one body to another, because the heart will continue to beat when put into another person’s body. The heart can be stopped for a short time during heart surgery, and then restarted by giving it a small electric shock.

What is the pulse?

                          The pulse is the throbbing beat that can be felt on the inside of your wrist and in the side of your neck. This regular beat is caused by the expansion of arteries near the surface of the skin. It happens each time the left ventricle in the heart contracts and sends another spurt of blood along the arteries.

What is the heart rate?

             Heart rate is the number of times that the heart contracts in a minute. You can measure this yourself by finding the pulse in your wrist, then gently holding your finger on it and counting the number of beats per minute. Don’t do this with your thumb because it has its own pulse!

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How does the heart work?

                     The heart is a fist-sized muscular organ that pumps blood around the body. It is actually two pumps that are joined together. At the top of each side of the heart is a thin-walled chamber called the atrium. It receives blood that returns to the heart through the veins. Once the atrium is filled, it contracts and squeezes its blood into a much more muscular chamber called the ventricle. The ventricle contracts in turn and forces blood at high pressure along the arteries and off to the lungs or the rest of the body. A system of one-way valves stops the blood from leaking back into the heart. The left side of the heart pumps blood around the body, while the slightly smaller right side pumps blood to the lungs to collect more oxygen. The blood circulation actually works in a figure-of-eight shape.

What is circulation?

                    Blood is pumped continuously around the body’s circulatory system. It is pumped in a continuous flow from the heart through the arteries, then through the tiny capillaries and back through the veins to the heart.

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What are blood vessels?

                          Blood flows around your body inside a network of tubes called blood vessels. There are three types of blood vessel: arteries, veins and capillaries. The blood in arteries comes straight from the heart and is pumped under pressure, so the artery walls are thick and muscular. Blood moves from arteries to veins through tiny capillaries, which are about one-tenth the thickness of a human hair. Capillaries are so narrow that red blood cells have to squash themselves up to pass through. Veins return blood to the heart, and because the pressure is now lower, they have thinner walls than arteries.

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Why can too much cholesterol be bad for you?

Cholesterol is a natural fatty substance that is found in many foods such as dairy produce, eggs and meat. It is also produced naturally in the body. High levels of cholesterol in the blood can sometimes collect on the inside of arteries, like the fur inside a kettle. This gradually reduces the blood flow and can lead to the formation of a clot that may break off and block smaller arteries. Sometimes an artery becomes almost completely blocked by these cholesterol deposits. It becomes so narrow and rigid that it cannot expand to let enough blood pass through. This kind of blockage usually happens in the legs, and is a common result of cigarette smoking.

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What is blood?

               Blood contains red and white blood cells that float inside a liquid called plasma. It also contains thousands of different substances needed by the body. Blood carries all these things around the body and also removes waste products. It is part of the body’s communication system, carrying chemical messengers called hormones that switch organs on and off as required.

                  Blood carries the white cells and chemical substances that attack invading bacteria and viruses. It also helps control body temperature. Red blood cells carry oxygen collected from the lungs to all parts of the body, releasing it where required. White bloods cells help protect the body from infection. They can produce disease-fighting substances called antibodies.

What are blood groups?

                 A blood group is a particular type of blood that may not match with other blood types when given in a blood transfusion. Blood groups differ from person to person. There are four main blood groups: O, A, B and AB. These letters refer to chemicals on the surface of red blood cells that are recognized by the body’s defences. When a person receives a blood transfusion, the blood groups need to be carefully matched to make sure that they are compatible.

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