Charactersistics of White Blood Cells or Leucocytes
Count – The number of leucocytes per microlitre of blood is called total leucocytecount (TLC). A normal adult human consists of 5,000–10,000/mm3 of blood. Rise in WBCs count is called leucocytosis. Increased TLC shows that there is acute bacterial infection.
Abnormal increased of WBCs called Leukemia (Blood cancer) and decrease WBCs count is called Leukopenia.
Shape – It is round or irregular shaped.
Size – WBC are larger than RBCs, size varies from 12- 20 μm.
Colour – Colourless.
Life Span- Normally 1-4 days.
Struture- A leucocyte contains cell membrane, nucleus and cytoplasm. Cytoplasm consists of mitochondria, gologibodies, centrioles and other cell organelles.
Types of WBC
Mainly there are two types of WBC.
1. Agranulocyte
It is leucocytes which don’t have granules in the cytoplasm. It is formed in red bone marrow, lymph nodes, spleen, bone marrow. Its volume is 28% of total WBCs. It is two types (a) lymphocytes and (b) monocytes.
- Lymphocyte – It is large sized and consists of round shaped nucleus. Its volume is about 20- 45% of total leucocytes. Its number is about 1680/mm3. It is formed in lymph nodes, spleen, thymus, tonsils, bone marrow, payers patches.
Life Span: Few days or months or even year up to 10 years or more.
Function: Motile, non- phagocytic in nature. It secretes antibodies and helps in healing. - Monocytes – It is the largest of all type of leucocytes. Cytoplasm consists of bean shaped nucleus. Its volume is about 2-10% of total leucocytes. Its number is about 280/mm3. It is formed in bone marrow.
Life span: 10 – 20 hrs.
Function: Motile and phagocytic in nature and engulf germs and foreign bodies.
2. Granulocytes
It is the leucocytes which have granules in the cytoplasm. The nucleus is lobulated or irregular shaped. It is formed in red bone marrow. Its volume is about 72% of total WBCs. It is of Three types
- Eosinophils (Acidophil) – It is acidic and its volume is about 1-6% of total leucocytes. It consists of bilobulated nucleus. Its number is about 105/mm3.
Formation: It is formed in bone marrow.
Life span: 8 hrs in blood and 4-5 days in tissue.
Function: Non-phagocytic in nature. It develops immune power (anti-allergic properties) and antihistamine properties. - Basophil – Cytoplasm consists of three lobulated nucleuses, less number of granules. It is basic stain and its volume is about 0.5%. Its number is about 35/mm3.
Formation: It is formed in bone marrow.
Life span: 8 hrs in blood and 4-5 days in tissue.
Function: Release the heparin (anticoagulant), histamine (vasodilator) and serotonin (vasoconstriction). - Neutrophils – Cytoplasm consists of many lobed nucleus and fine granules and acidic as well as basic stain. Its volume is about 75% of leucocytes. It s number is about 4900/mm3.
Formation: It is formed in bone marrow.
Life span: 4-8 hrs in blood, 4-5 days in the tissues.
Function: It is phagocytic in nature and engulfs germs and dead cells.
