Apart from red cells, there are the white cells or leucocytes. Some are produced by the bone marrow and are called granulocytes, because they have varying coloured granules dotted throughout them when stained ready for examination under the microscope.
There are three kinds of granulocytes. One form, called the neutrophil, has the capacity of engulfing and devouring foreign particles in the blood. They are termed phagocytes, and this capacity is necessary to combat infections. The germs are simply gobbled up by the cell, digested and destroyed. Incidentally, the white cell dies also – a case of giving its life to help keep the owner alive. This is seen in the formation of pus.
There are two other types of granulocytes: the eosinophils (that stain a bright red) and the basophils (that turn blue on staining). The eosinophils are associated with allergic reactions, being present in higher numbers in patients with allergies (such as asthma and hay fever) and parasitic infections. Basophils are involved in inflammatory and allergic reactions.
So much for the red cells. They seem very important. Now what about the white cells you spoke of? These are also extremely important. They are really the fighting force of the body. Their task is essentially one of protection. In time of need they are mobilised, and they vigorously attack any unwanted foreign invaders that may harm the system. There are many different kinds, but they are essentially there for the same purpose.
If infection occurs at any part of the system, the white cells congregate, and actively attack the germs. They actually approach them, roll over them and totally encompass them in a weird process called phagocytosis. When this has happened, the cell usually dies, with the germ inside it. This is how pus forms – it’s really a collection of millions of dead white cells and dead germs.
In times of infection, huge numbers of white cells are manufactured rapidly by the system, and thus the “white cell count” of the blood increases, as the doctors say. This condition is called leucocytosis – the leucocyte being the official name of the white cells. Sometimes there is a swing in the opposite direction, and there are insufficient white cells. This is called leucopenia, and may be dangerous if an infection strikes.
Where do the cells come from?
There are many different places around the body where they are manufactured. The softish material in the centre of the large bones of the limbs called marrow is an important one. Others are made in the lymph glands, and two large organs located in the upper part of the abdomen called the liver and spleen are also associated with the cells. A gland in the upper part of the chest of children, called the thymus, also produces certain types of white cells. Another solid part of blood are the platelets, microscopic particles that play an important part in blood clotting