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| Sunday, 30 April 2006 |
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Junior Observer |  |
| News Business Features Editorial
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The fluid of life Have you heard people use the phrase "blood is thicker than water," especially when they are talking about family connections? Blood, the sticky, red fluid is three times thicker than water. It is the body's transport system, circulating continuously throughout its complicated network of veins, arteries and capillaries. Without blood, the body cannot work; cannot survive. Blood, truly, is the fluid of life itself. The blood accounts for a sixteenth of our body weight. And what organ has a major role to play in the circulation of blood? The heart of course. At rest, the heart pumps 5-6 litres of blood in an average man or 4-5 litres in the average woman, to the lungs and other tissues, each minute. During exercise, as much as 50 pints (28 litres) or more a minute may course through the vessels. What blood does... * The blood supplies life-sustaining oxygen. * It delivers vitamins, minerals and other essential nutrients from digested food. * It carries hormones from glands to control many vital functions. It helps fight infections. * It cleanses the tissues, exchanging carbon dioxide for oxygen and removing other wastes to the kidneys. * It also distributes warmth.
Nearly half the blood (45 per cent) consists of blood cells - red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes). Most of the rest (55 per cent) is plasma, a clear, watery, pale yellow fluid.New blood cells are constantly being made inside the bones to replace old ones as they die off or are lost through illness or injury. Did you know that one small drop contains millions of cells? In one drop of blood, there are five million or more disc-shaped red blood cells, which live for about three months. These cells contain haemoglobin, a red iron-containing protein that gives blood its colour. Haemoglobin carries oxygen from the lungs to the tissues, and also contains enzymes, minerals and sugars.
White blood cells are bigger, but less in number and do not live as long as red cells. They cleanse the body and are its main defence against infections and cancers. In one drop of blood, there are from 7,000 up to as many as 50,000 white blood cells, depending on the body's needs at that time. Some produce protective antibodies (substances that destroy harmful germs), others surround and devour invading micro-organisms. There are several types of white blood cells, which also destroy bacteria important for the immune system, and make heparin, an anti-clotting substance. Platelets are much smaller than red or white cells, with 250,000 in a single drop. They clump together to stop bleeding. Without them, you could bleed to death. The presence of both clotting and anti-clotting agents in the blood ensures a balanced system. What is blood plasma? Blood plasma, which carries the cells and platelets, consists chiefly of water, with about as much salt as sea water, plus thousands of other dissolved constituents - nutrients, wastes, proteins, hormones, salts and minerals. Measurement of the levels of these substances helps diagnose illnesses. How and why does blood clot? Whenever you cut or wound any part of your body, you may have noticed how blood initially oozes out, but start to reduce gradually, and finally stops. This is due to clotting. In normal clotting, platelets start to clump together within seconds of the skin being cut. They adhere to the damaged wall of the blood vessel and change their shape from discs to spiny spheres, which enmesh with each other and a clot develops.
However, these same platelets can also contribute to unwanted clots, and add to fatty deposits building up on blood vessel walls (atherosclerosis), which is a major cause of heart attacks and strokes. How does a blood clot form? Calcium, vitamin K and a protein called fibrinogen help the platelets form a clot. They are released by platelets and stimulate coagulation of the blood. Altogether, 13 different coagulation factors, all essential for health, are involved in blood clotting. Without calcium and vitamin K, blood takes longer than normal to clot. In the final step of the clotting process, threads of fibrin, a stringy protein, help to plug the injury with a web-like mesh that traps the blood cells within it. This web hardens as it dries, contracting to form a clot or scab. A bruise, too, is the result of a blood clot. Blood groups Every person doesn't have the same blood type. There are different types of blood which have been categorised as groups. Blood groups differ according to proteins known as antigens on the surface of red blood cells. Blood group matching is essential for safe blood transfusions. In the early 20th century, two types of antigen, A and B, were discovered. The combination of these types produces four blood groups: type A, type B, type AB (both antigens) and type O (neither A nor B antigen). Disorders can affect any of the blood's components. The most common is anaemia, which usually arises from iron deficiency in oxygen-carrying haemoglobin. Anaemia can lead to headaches, tiredness and lethargy and, if more severe, breathing difficulties and heart problems. There is a group of disorders where abnormally prolonged or excessive bleeding may occur anywhere in the body after injury or even in the absence of injury. One well-known, but fortunately rare, example of this is haemophilia, an inherited condition in which even the slightest injury can produce potentially fatal internal or external bleeding. ***** What you can do to maintain healthy blood Blood contains living cells so, just like any other part of the body,
they need good nutrition. A balanced diet with ample fresh fruit and
vegetables is the key to ensuring the mix of vitamins and other essential
nutrients. |
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