White Blood Cells (WBCs)
- White Blood Cells (WBCs), also known as Leukocytes.
- WBCs are colorless cells, lacking hemoglobin, and are nucleated.
- They are relatively fewer in number compared to red blood cells, averaging between 6000 to 8000 per mm³ of blood.
- WBCs are generally short-lived cells.
Classification of WBCs:
WBCs are classified into two main categories based on their structure: granulocytes and agranulocytes.
Granulocytes:
- Granulocytes contain granules in their cytoplasm, visible under a microscope.
- The three types of granulocytes are neutrophils, eosinophils, and basophils.
1. Neutrophils:
- Neutrophils are the most abundant type of WBC, comprising 60-65% of the total WBC count.
- Function: Neutrophils are phagocytic cells, meaning they engulf and destroy foreign organisms entering the body, such as bacteria and fungi. They play a crucial role in the body's innate immune response against infections.
2. Eosinophils:
- Eosinophils make up about 2-3% of the total WBC count.
- Function: Eosinophils are involved in resisting infections and are associated with allergic reactions. They help combat parasitic infections and modulate allergic responses by releasing chemical mediators.
3. Basophils:
- Basophils are the least abundant type of WBC, comprising only 0.5-1% of the total WBC count.
- Function: Basophils secrete substances such as histamine, serotonin, and heparin, which are involved in inflammatory reactions and allergic responses. They play a role in the body's defense against pathogens and contribute to the inflammatory response.
Agranulocytes:
- Agranulocytes lack visible granules in their cytoplasm.
- The two types of agranulocytes are lymphocytes and monocytes.
1. Lymphocytes:
- Lymphocytes make up approximately 20-25% of the total WBC count.
- Function: Lymphocytes are responsible for specific immune responses and play a crucial role in adaptive immunity. They include B cells, which produce antibodies, and T cells, which directly attack infected or abnormal cells.
2. Monocytes:
- Monocytes account for about 6-8% of the total WBC count.
- Function: Monocytes are phagocytic cells involved in engulfing and destroying pathogens and cellular debris. They play a role in the body's immune response and contribute to tissue repair and inflammation.
Platelets, also known as Thrombocytes:
- Platelets are small, disc-shaped cell fragments produced from megakaryocytes, which are specialized cells found in the bone marrow.
- Blood typically contains between 150,000 to 350,000 platelets per mm³.
- Platelets play a crucial role in blood clotting, also known as coagulation or hemostasis.
- When blood vessels are damaged, platelets adhere to the site of injury and aggregate to form a plug, preventing excessive bleeding.
- Platelets release a variety of substances, most of which are involved in the coagulation process. These substances include clotting factors, enzymes, and chemicals that promote clot formation.
- Clotting factors interact with platelets and other blood components to form fibrin, a protein network that stabilizes the clot and prevents further blood loss.
- Platelets also release growth factors that stimulate the repair and regeneration of damaged blood vessel walls, contributing to the healing process.
- Platelets are essential for maintaining hemostasis and preventing excessive bleeding.
- A reduction in platelet count, known as thrombocytopenia, can lead to clotting disorders, increasing the risk of excessive bleeding and hemorrhage.
- Platelet disorders or abnormalities can result in impaired clot formation, leading to prolonged bleeding times and increased vulnerability to injuries and bleeding disorders.