Types of blood cells and their functions and images

Blood cells types

45% of blood cells are found in blood. It is of three types:

(i) Red Blood Cells (RBCs) or erythrocytes (ii) White Blood Cells (WBCs) or leucocytes    (iii) Platelets or thrombocytes

Blood cells

(i) Red Blood Cells (RBC)

The unique feature of RBCs is the presence of a red, oxygen-carrying pigment, the hemoglobin, In their cytoplasm. The shape and size of RBCs vary in different animals. 

The cells may be uninucleated or non-nucleated. In almost all the vertebrates, except mammals, these are nucleated, oval and biconvex. In mammals, these are non-nucleated, biconcave and circular. 

Actually, the nucleus is present in the RBCs of mammals initially but when these cells are finally differentiated and mature, the nucleus, mitochondria and endoplasmic reticulum are degenerated. 

If we talk about human body, the amount of RBC in blood cells is 90%. Its life is 120 days. RBCs are born in the human body in the bone marrow and die in Spleen. Spleen is also known as RBC cemetery. The function of RBC is to conduct oxygen and carbon dioxide.

RBC deficiency diseases

Anemia, jaundice etc.   

(ii) White Blood Cells (WBCs) 

 These are colourless, nucleated and motile (amoeboid) cells of blood, much larger than RBCs, but less in number. All leucocytes are capable of amoeboid movement. These are of two main kinds; phagocytes and immunocytes. 

Phagocytes are capable of phagocytosis and they carry out the function of body defense by engulfing bacteria and other foreign substances.

 If we talk about the human body, the amount of WBC in blood cells is the lowest. It has a life of 3-4 days. The WBC is born in the human body in the bone marrow and dies in blood. 

Vitamin A increases WBC in blood. The decrease in the amount of WBC is called Leukopenia. Excess of WBC is called Leukemia. WBC is of three types:

 (a) Granulocytes: 

They have irregular shaped nuclei and cytoplasmic granules with specific staining properties. They include eosinophils, basophils and neutrophils.

 (b) Agranulocytes: 

These are non-granular leucocytes, having a roughly round or indented nucleus and clear cytoplasm. They include monocytes. They ultimately migrate to body tissue and transform into macrophages and histocytes.

 (c) Immunocytes: 

They produce antibodies and are involved in immune response. They include lymphocytes that contain central, spherical nucleus and a little cytoplasm with no granules and produce antibodies.

 WBC deficiency diseases

 Blood cancer etc.

 (iii) Blood platelets or thrombocytes: 

These are minute, highly contractile, round or oval, biconvex discs with granular cytoplasm, but without nucleus. As is recently discovered, the platelets are fragments which form as buds and pinch off from certain large cells (megakaryocytes) in bone marrow. They help in the clotting of blood in the site of injury to a blood vessel, so as to prevent further loss of blood.

 Platelet deficiency diseases

Chikungunya, Dengue etc.

Occurrence

It occurs in blood vessels called arteries, vanes and capillaries that are connected together to form the circulatory system. The highly branching network of vessels enables blood to reach every part of the body.

Blood cells function

Ø    It transports oxygen from respiratory organs to various body tissues.

Ø  It carries carbon dioxide from body tissues to respiratory surfaces like lungs, skin, etc.

Ø   Digested food absorbed from the intestine is carried to different parts of the body.

Ø     It carries excretory wastes produced in the body to kidneys for elimination.

Ø     It maintains the body temperature.

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Ishan Kumar