Category Zoology

Why does the body have skin?

                Skin is a flexible, waterproof covering that protects us from the outside world. It prevents harmful germs from entering the body. Skin is your largest organ, and it is sensitive to touch, temperature and pain. Your skin tells you what is happening around your body, so you can avoid injuring yourself. Also it helps to prevent damage from the Sun’s harmful ultraviolet rays. Skin also helps to regulate body temperature by sweating and flushing to lose heat when you get too hot.

Is skin alive?

              All the skin cells that you can see are dead! Your body is constantly producing new skin cells from beneath the surface skin layer that you can see. As new cells push upwards towards the surface, the older cells on top become flattened and eventually die. The dead cells form a protective layer that constantly flakes away like dust.

Why do people have different skin colours?

                    Skin colour is caused by a dark pigment called melanin in cells below the skin’s surface. Melanin filters out harmful ultraviolet light from the Sun, preventing damage to the tissues beneath the skin. People originating from hot countries have developed extra melanin in their skins for Sun protection, so their skin is darker.

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Why do people sweat?

                    Sweating removes excess salt and wastes through the skin. It also helps to keep you cool, because sweat takes heat away from the body as it evaporates on the skin. If you have been exercising and are very sweaty, and then stand in a draught, you will notice this cooling effect very quickly. Sweat is a watery liquid, but other skin glands release an oily substance called sebum that helps to lubricate the skin and keep it supple.

Why do I need to sleep?

            You spend about one-third of your life asleep, but no one is sure why this is necessary. During deep sleep, the body produces large amounts of growth hormone that help to repair or replace damaged cells and tissue. Sleep also speeds healing. While you are sleeping, the brain remains very active. The body goes through stages of being very limp and relaxed and other stages when the eyes move about beneath closed eyelids. Dreaming takes place during this rapid eye movement period, called REM sleep. Dreaming is very important. If you prevent someone from dreaming by waking them every time they enter REM sleep, that person can become very disturbed and ill after several dreamless nights.

How does the body repair damaged tissues and cells?

Cells are able to divide very quickly to replace those that are old or have died. Nerve cells are the only ones that cannot be replaced. However, even nerve cells can sometimes grow new connections if the long fibres along which messages are passed become damaged. Dead and dying cells are removed by white blood cells in the blood stream, which actually eat them. The liver is also able to break down red blood cells, which are only able to survive for a short time.

What job do the kidneys do?

                  Kidneys are very effective at removing most of the waste from our blood.

                   Blood is pumped through groups of tiny tubes inside the kidneys, and harmful waste material passes out through the walls of these vessels and down a long tube called the ureter, into the bladder. Here it is stored until ready to be discharged from the body as urine. The kidneys have a very important function in controlling the amount of water in the body. Water balance needs to be kept at exactly the right level if the body cells are to remain healthy.

 What is a kidney machine?

If the kidneys become diseased and stop working, it is necessary to use a kidney machine to remove waste from the blood. This machine process is called dialysis. It involves pumping blood from a tube in the person’s arm into thin tubing that runs through a tank of sterile liquid. Waste passes from the blood through the walls of the tubing, and the cleaned blood is returned to the body. This has to be done throughout the person’s life, unless a new kidney can be provided in a transplant operation. Dialysis needs to be carried out frequently — several times a week — to stop wastes from building up to dangerous levels.

How does the body keep at the proper temperature?

The body has several systems to keep itself at the right temperature. Heat is produced by the breakdown of food substances stored in the body. The chemical reactions in the body will only take place properly if the body is kept at the ideal temperature, so any extra heat has to be removed. Heat leaves the body through the lungs, as you breathe out warmed air, and also through the skin. If you are very hot, the blood vessels near the skin’s surface open wider to increase the blood flow, so you look a bit pink. The extra blood means more heat leaves the skin surface, so cooling your body.

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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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