White blood cells are blood cells responsible for protective our body from harmful foreign particles, infection and diseases. The first cells that reach to the injured site is of WBC. They are called as defense cell or system of the body. WBC also called as leukocytes.
What are white blood cells?
White blood cells (leukocytes) are part of immune system, they are of only 1 percent of total blood volume. This blood cells exit the capillaries when they see any infection, bacteria or damage to cells. Thereafter this cells act on those cells and bacteria, kill them and again enter into the blood capillaries.
Structure
The structural characteristics of white blood cells are given below,
- Unlike RBC, WBC have their own nuclues and cellular organelles
- WBC does not have any particular color (colorless/ translucent)
- Diapedesis – This tells about their shape. They generally has round shape. But that can be changed or squeeze to exit from the capillaires to reach towards the infection site. This process is called as diapedesis.
- WBC contains various types of enzymes and granules to destroy harmful micro organism
Characteristics of WBC
- Colorless cells
- Have nucleus and cell organelles
- Shape is large than RBC
- Can be move from capillaries to outside and vice versa
- Important part of immune system
Types
White blood cells are classified into two categories based on presence and absense of granule.
- Granulocytes (contain granules)
- Neutrophils
- Eosinophils
- Basophils
- Agranulocytes (lack granules)
- Lymphocytes
- Monocytes
Neutrophils
Neutrophils contribute to 50 to 70% of the total white blood cells. This are the primary cells that are responsible for arriving at site of infection. They firs engulf and digest bacteria through a process called as phagocytosis.
Eosinophills
Eosinophills contain only 1 to 4% of total WBC. They help in fighting with parasitic infections. They also play important role in allergic reactions and asthma response.
Basophills
Basophills contain only 0.5 to 1% of wbc. They release histamine (it causes dilation of blood vesels) and heparin (anti-coagulant), it helps white blood cells to reach in more quantity at the injured site.
Lymphocytes
Lymphocytes contain of 20 to 40% of the total WBC. There are three sub types as B cells, T cells and Natural Killer cells. B cells develops antibodies and kill pathogens, t cells directly attack on infected cells and destroy it. Natural killer cells attack on the virus infected cells and tumor cells. Lymphocytes are also important for coordinating the immune system response.
Monocytes
Monocytes are of 2 to 8% of total wbc count. This are largest of all wbc cells, they move from capillaries to tissues and form as macrophages and dendritic cells. Thereafter, they remove the cell debris and also send pieace of pathogen to lymphocytes to develop long term memmory.
Functions
1. Phagocytosis – The primary function of wbc are to ingest the harmful foreign invadors and cellular debris.
2. Antibody production – WBC specialized cells such as b cells and t cells create antibodies and tag the harmful foreign particles then create an immune response against them.
3. Inflammattory response – WBC are essential in carrying out the primary immune response as inflammation. They release histamine which dilates blood flow and increase the number of rbc at injured sites.
4. Develop memmory – WBC remember the infection once happen to your body. So next time if same infection occurs then body will react very aggressively. The chance of developing disease is reduced due to memmory.
Normal Count of WBC
WBC normal count is 4,500 to 11,000 cells per microliter of blood for an adult person. WBC higher than 11,000 is referred as leukocytosis and lower than 4500 is called as leukopenia.
Lifespan of WBC is depend on type of white blood cells are given below,
Neutrophils – 6 hour to 5 days, Esoinophils – 8 to 12 days, Basophils are for few days and monocytes are for 1 to 3 days. Only the lymphocytes that store memmory b and t cells can live for weeks to years.