Blood Components

Blood Components

Blood is:

is a way of transport of substances and gases (for example oxygen) from one part of the body to another.
it is a defense mechanism against foreign bacteria and substances, example, to fight against infections.
and it regulates body temperature.

Blood is composed of the liquid part and the solid part. The liquid is called plasma, a yellowish slightly viscous liquid, made up of dissolved proteins and salts. The solid part of blood is made up of cells (small round discs which can be seen only by microscope). There is approximately 55 % plasma and 45 % solid part (cells floating in this plasma).

There are three main types of cells in the solid part of blood. These are:

Red blood cells (erythrocytes),
White blood cells (leucocytes) and
Platelets (called also thrombocyte).


The red cells are the cells responsible for the red colour of blood and constitute 75% of the solid part of the blood. They contain a complex protein called haemoglobin, which is necessary to carry oxygen from the lungs to the cells of the whole body. This haemoglobin needs iron to be formed. One takes iron tablets when “blood level” is low (anaemic), to help the formation of haemoglobin in the red blood cell. Vitamin B12 is needed to help in the formation and development of this red cell in the bone marrow. The life span of the red cell is approximately 120 days when it is replaced by new ones.		The white blood cells (leucocytes) constitute 25% of the solid part of the blood and are divided into 2 main types, the granular leukocyte (granulocyte) and the non-granular leukocyte. Further more there are 3 types of granulocytes (neutrophils, eosinophils and basophils) and three types of non-granular leucocytes (monocytes, small lymphocytes and large lymphocytes). These white blood cells (especially the neutrophils) are involved in the fight against foreign bacteria (infections) and foreign elements. Additionally (especially the lymphocytes) white blood cells build up a defense mechanism to combat similar future infections, and next time one would not be affected by the infection. This process is called immunity.

White Blood Cell (Leukocytes)

Granular cell (granulocytes, 75%)

Non-granular cells (25%)

neutrophils

small lymphocytes

basophils

large lymphocytes

eosinophils

monocytes

The platelets are minute cells and they play a very important part in the clotting of blood. The liquid part of blood (plasma) contains many-dissolved substances among which are the clotting factors. The main clotting factors are: prothrombin, calcium, and fibrinogen. When there is a cut, thromboplastin is released from body tissues into the blood. When thromboplastin meets with the above-mentioned clotting factors and platelets, a series of chemical reactions starts. Ultimately in healthy persons a blood clot is formed to stop bleeding. That is why patients with bleeding disorders are transfused plasma or its products because only clotting factors are needed to correct the disorder. Here is a brief summary of what happens in a bleed.

prothrombin + calcium + thromboplastin (from damaged tissues) = thrombin
thrombin + fibrinogen = fibrin (fine threads)
fibrin + platelets = blood clot (mesh or net)