Blood

Blood is an important fluid that keeps us alive. We cannot live without it. The heart pumps blood to all parts of the body and brings them oxygen and food. At the same time blood carries all the substances we don’t need away from us. Blood fights infections, keeps our body temperature the same and carries chemicals that control body functions. Finally, blood has substances that repair broken blood vessels so that we don’t bleed to death.

What blood is made of

Blood is a mixture of fluid and solid matter.
Plasma is the liquid part of our blood. It makes up about 50 – 60 % of it. Plasma consists mostly of water but many other substances are in it. It contains dissolved food, chemicals that control our growth and do other jobs, proteins, minerals and waste products.
Red blood cells look like flat round discs. They contain haemoglobin, a protein that carries oxygen to the body and gives blood its red colour. Each drop of blood has about 300 million of these red cells.
White blood cells, also called leukocytes, fight infections and harmful substances that invade the body. Most of these cells are round and colourless. They have different sizes and shapes. White blood cells are not as numerous as red ones. For every 700 red blood cells there is only one white blood cell.
Platelets are tiny bodies that are much smaller than red blood cells. They stick to the edges of a cut and form blood clots to stop bleeding. The blood of a normal adult has about 2 trillion platelets.

 

How blood works in the body

 

The blood stream of our body

Food also reaches your body by means of blood. It is digested in your stomach and important substances like fat, sugar, proteins, vitamins and minerals are separated. These nutrients enter your blood stream and are moved to the cells and muscles where they are needed in order to give you energy or fuel. The work of the muscles and other tissue creates heat. Blood is the transporting system which carries heat throughout your body and warms you. The things that you don’t need are transported to your intestines and kidneys and leave your body again.
White blood cells play an important role in your immune system. When harmful substances invade your body an alarm goes off and white blood cells are activated. Then they work to destroy the invaders. They fight off viruses, harmful bacteria and begin anti-body production.
Blood also carries hormones to places where they are needed. When a hormone reaches a part of the body it controls growth, how the body uses food and other things.
You would bleed to death from a small cut if your blood didn’t clot. When a blood vessel breaks platelets rush to the damaged area and stick to one another , forming a plug.

The blood supply

 
Blood cells come from bone marrow. They begin as stem cells and then develop into red or white blood cells, or platelets. They don’t live forever and must be replaced by new ones. Red blood cells live an average of 120 days before wearing out. Then they are captured and destroyed in the liver and spleen. Platelets live only for about 10 days.
The amount of blood in your body depends on your size, weight and the altitude at which you live. An adult who weighs 80 kg has about 5 litres of blood, a 40 kg child about half the amount. People who live in high areas where the air is thinner need more blood to deliver more oxygen to the body.

 

Blood groups

Blood groups are very important in order to find out if a person can donate blood or receive blood in case of an accident or another disease. Almost everyone’s plasma has antibodies that that may not work together with another person’s blood.
There are four main blood groups :

• Type 0 is the most common blood group. In an emergency type 0 blood can be transfused to anybody.
• Type AB is the most seldom group. People with this blood group can receive any other blood in case of an emergency.
• Type A can only be received by donors with A or 0.
• Type B can only be received by donors with B or 0.

Blood Groups

 

 

Blood transfusion

If an adult suddenly loses a litre or more of blood he may die unless the blood in his body can be replaced. Over the years blood transfusions have saved countless lives. Transfusions can also help patients who cannot produce enough blood cells to survive. They also help during operations when patients lose some blood.
Blood banks collect blood from donors and put it in sterile bags. It is cooled down and can be stored for up to 50 days. Laboratory workers screen blood for infectious diseases like AIDS and hepatitis. Only clean and safe blood can be given to patients.
 

Blood diseases

When a person suffers from anaemia there are not enough red blood cells to supply the body with the oxygen he needs. Leukaemia is a kind of cancer of the bone marrow, in which not enough or abnormal white blood cells are produced. Without white blood cells diseases can enter your body without being controlled.
When your body does not have enough platelets blood cannot clot well. Even small injuries can lead to a loss of blood because bleeding doesn’t stop.