Category Human Body

How does the body keep itself working properly?

                   Millions of chemical reactions take place in the body, and because they can influence one another, they all need to be kept in balance. This process is called homeostasis, and it ensures that the whole complicated system works smoothly, and that problems are usually overcome before they can cause illness. The brain monitors what happens within the body and controls everything by means of nerves and chemical messengers called hormones that switch chemical reactions on and off as needed.

What is excretion?

                    Excretion is the removal of waste material from the body. Most of this material is removed from the blood by the kidneys, but waste carbon dioxide produced by the activity of the cells is removed by the lungs, and other waste is excreted as sweat, through the skin. The liver gets rid of many poisonous materials by making them harmless and passing them on to the kidneys.

What is urine?

                     Urine is the liquid produced in the kidneys and discharged from the bladder when we pass water. It contains waste materials.

What happens to food in the stomach?

                          Food in the stomach is churned up with acid and digestive juices that start to break it down. This is the beginning of digestion. The stomach wall is covered with a layer of mucus that stops it from digesting itself. The acid in the stomach helps digestion, and also kills bacteria that have been swallowed with the food.

What is the appendix for?

                    The appendix is probably a leftover from our very ancient ancestors, and in humans it has very little use. In animals that eat a lot of plant material, such as rabbits, the appendix is large and contains bacteria that help digestion. The human appendix is a tiny finger-like projection from the lower part of the gut. It sometimes becomes inflamed and has to be removed surgically.

What happens in the small intestine?

Most of the process of digestion takes place in the small intestine. Food is broken down into simple substances that can be absorbed through the gut wall into the blood. Most of these food substances are carried in the blood to the liver, a large organ in your abdomen. The liver stores them until they are needed. The liver has many other useful functions in cleaning the blood and removing old red blood cells. It breaks them down into greenish liquid called bile, which is used to help the body digest fats. The digestive processes in the small intestine and the rest of the digestive system depend upon having the right amount of acid or alkali present.

Why do I have different types of teeth?

                      Teeth have different shapes so they can carry out different jobs. Incisor teeth at the front of the mouth are flat and shaped like chisels. You use them to cut your food. The canines are the pointed teeth just behind the incisors, and you use them to tear food. The back teeth, called molars and premolars, are flattened so they can grind the food into small pieces ready for swallowing.

What are teeth made of?

                       Teeth are made of a hard material that similar to bone .They are covered with shiny enamel to protect them from attack bacteria. Teeth are hollow, and contain blood vessels and nerves. They are rooted into jaw. Teeth start to grow before you are born, and begin to appear through the gums at about the age of six months. The adult begin to replace a child’s milk teeth at about six years of age.

How do I swallow food?

                  Swallowing is a complicated muscular process. Your tongue forces food to the back of your mouth and into the throat. At the same time the soft part of the roof of your mouth closes off the air passages to your nose, and a small flap called the epiglottis closes off the passage to your lungs so you do not inhale the food. You can actually swallow upside down because the food is carried along the digestive system by muscular waves. Astronauts are able to swallow when there is no gravity to help carry the food down their food pipe.

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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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