THE WHITE BLOOD CELLS
everywhere in the environment and have continuous access to the body
through the mouth, nose and pores of skin. Further more, many cells
age and die daily and their remains must be removed, this is where
the white blood cell plays its role…
white blood cells, make up a small fraction of whole blood. However,
they have vital functions in keeping the body healthy and clearing
away dead cells from the body. Some leukocytes scavenge dead or
worn-out cells, others target or destroy specific bacteria, viruses,
and other agents of disease.
White cells fall into two major
groups. One group is know as the granular leukocytes.
They are so called because they have large characteristic granules in their cytoplasm that can be see under a light microscope. All of them are very much smaller than the red cells, their average size about 1/700 of a red cell. However, their duty is no less important than the red cell.
There are many different types of
- Neutrophil - its average size is 10-12 micrometers in diameter. The nucleus is made of 2 -5 lobes, connected by thin strands of chromatin. Its cytoplasm has very fine, pale lilac
- Eosinphil - its nucleus is made of two lobes, and embedded in the cytoplasm are large, red-orange granules.
- Basophil - it have bi-lobed nucleus and its granules appear deep blue-purple.
Apart from granular white cells, the other group is collectively known as agranular white cells.
This is simply because their cytoplasmic granules cannot be seen with an ordinary light microscope. Under this group are the Lymphocytes and the monocytes.
Most of the white cells carry out
phagocytosis, i.e. they collect at the site of infection, engulf and ingest the bacteria, thereby preventing the spread of infection.
Neutrophils and monocytes are actively phagocytic, which means they can ingest bacteria and dispose of dead cells. Once they reach the site of infection, they release certain enzymes such as lysozyme, to destroy the harmful bacteria.
©Copyright TQ Team 25896, 1999. The Circulatory System- Online Learning.