White blood cells or leucocytes are colorless, irregularly shaped and bigger sized cells than the R.B.C. containing nucleus. They are fewer in number, about 8,000 in males and 7,000 in females per cubic millimeter of blood. Their life span is shorter, which varies under different conditions and environments and is estimated as four days or more. W.B.C. is rich in nucleoprotein and contains certain fats, glycogen, cholesterol, vitamin-C and variety of enzymes.
The average rate of W.B.C.: RBC is 1: 700. They grow in red bone marrow, lymph gland, spleen and other lymphoid tissues. They are constantly changing their shapes and resemble amoeba (small microscopic animal found in pond water). Consequently, their movements are described as amoeboid movement. By means of this movement, they are capable of moving from one place to another and even getting out through the thin walls of the smallest blood vessels.
There are several varieties of W.B.C. each type possessing characteristic structure and staining property. They may be divided into two main groups.
These cells make up about 75% of the total white-cells. They are made in the bone marrow and survive for 21 days. These cells contain a many-lobed nucleus and the protoplasm of the cells is granular. The granules may take either of the three different stains-neutral (purple), acid (red), or basic (blue). Granulocytes may be classified according to their staining properties as:
The nucleus of neutrophils is many-lobed and absorbs both acid and alkaline dyes. They have the ability to ingest the small particles (bacteria or debris). This power is called the phagocytosis. By the amoeboid movement, they can pass out of the blood stream through the capillary walls, to accumulate where there is infection. On the whole, these cells are actively motile and highly phagocyte.
These are characterized by large coarse granules which take acid stains very readily. Normally, there is two or more lobed nucleus which takes basic stains. Normal percentage is 2-4.They are found in increasing number in chronic bronchitis, asthma and in certain allergic conditions.
The have coarse, granules which takes basic stains and have a single nucleus, sometimes blobbed and deeply stained.
Agranulocytes is of two types:
These are non-granular cells and constitute about 25% of the total number of white cells. They are made in the lymph nodes and in the lymphatic tissues, which is present in the spleen, liver and other organs. They show some amoeboid movement, but are not actively phagocytic. They are concerned with the production of antibodies.
These make up about 5% of the total white cell count. They are the largest of the white blood cells and have a horse-shoe shaped nucleus. They are most powerfully phagocytie and act, mostly as scavengers.
Functions of white Blood Cells:
White blood cells perform several functions in the body as:
The neutrophils and the monocytes engulf foreign particles and bacteria through their phagocytoic action, thereby destroying their action.
2. Body defense:
W.B.C. manufactures anti-bodies and immune bodies to increase the power of resistance against any infection.
3. Formation of fibroblast:
Lymphocytes may be converted to fibroblast in the area of inflammation and help the process of tissue repair and regeneration.
4. Secretion of heparin:
The basophile leucocytes are supposed to secrete heparin (a substance of liver), which prevent, intravascular clothing.
5. Anti histamine functions:
The eosinophils are very rich in histamine. They are believed to defend the body against allergic conditions in which histamine like bodies are produced in excess.
6. Production of thromboplastic substances:
Due to the production of such substances, the process of coagulation and the deposit of clot are facilitated.
7. Manufacture of trephones:
Leucocytes manufacture certain substances called trephones from plasma protein, which exert great influence on the nutrition, growth and repair of tissues.