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White Blood Cells
White Blood Cells (Leucocytes)
White
blood cells are responsible for the defense system in the body. There are
approximately 6,000 white blood cells per millimeter of blood or ˝ a million
white blood cells in every drop of human blood. White blood cells fight
infections and protect our body from foreign particles, which includes harmful
germs and bacteria. White blood cells, the red blood cells are formed from the
stem cell of the bone marrow. It has a life-span of a couple of days. When they
die, they are destroyed by surrounding white blood cells and replaced with new
ones.
Structure of White Blood Cells
| White
blood cells are colorless without haemoglobin. It contains a nucleus and has an
irregular shape. Though there are fewer white blood cells than red blood cells,
they are much bigger in size. They can change their shape easily and this allows
them to squeeze through walls of the blood vessels into the inter-cellular
spaces. |
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Types of White Blood Cells
Unlike the Red blood cells or platelets, there are 5 different types of white blood cells, each serving a different purpose in our body’s immune system.
Neutrophils
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Neutrophils make up 55%-70% of the total white blood count in the
bloodstream. They have a segmented nuclei and it is said to be ‘C’ shaped.
Neutrophils can be most commonly found near sites of infection or injury where
they will stick to the walls of the blood vessels and engulf any foreign
particles that try to enter the bloodstream. They can also be found in the pus
of wounds.
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Eosinophils
Eosinophils make up 2%-5% of the total blood count and mainly attacks
parasites and any antigen complexes. These cells are also responsible for
allergic response within the blood.
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Basophils
Basophils make up less than 1% of the total white blood
count. They secrete anti-coagulant and antibodies, which mediate
hypersensitivity reactions within the blood. They are known to have phagocytory
features though they are more often related to immediate immune reaction against
external germs and diseases.
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Monocytes
Monocytes, though having only 5%-8% in the total white
blood count, are the largest of the 5 types of white blood cells. They act as
tissue macrophages and remove foreign particles and prevent the invasion of
germs which cannot be effectively dealt with by the neutrophils. They have been
known to have phagocytic functions. |
Lymphocytes
Lymphocytes produce anti-bodies against toxins secreted by
bacteria and infecting germs. These antibodies will be excreted into the plasma
to kill bacteria in the blood as well as act as anti-toxins. These anti-bodies
will cause the foreign particles to cluster together, rendering them easily
engulfed by the phagocytes. However, the nature of lymphocytes is highly
specific and they can only recognize certain antigens. |
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