Blood is the only fluid connective tissue in the human body and it is involved in the transportation, regulation, and maintenance of body temperature, pH, and other thermoregulation processes. A healthy individual will have about 5 to 5.5 liters (1.5 gallons) of blood.

Blood is generally composed of:

  • Red Blood Cells (RBCs),
  • White Blood Cells (WBCs),
  • Blood Platelets,
  • The Plasma.

Here, in this article let us explore more in detail about the White blood cells.

White blood cells are also termed as the Leukocytes. They are nucleotide blood cells, which are differentiated into granulocytes and agranulocytes. They play a vital role in maintaining a healthy immune system. These blood cells are called white blood cells (WBC) because of the cells which are white in color. On an average, there are between 4,000 and 11,000 cells in every microliter of blood, and a healthy person will produce around 100 billion of white blood cells every day.

Types of White Blood Cells

There are five different types of White blood cells and are classified mainly based on the presence and absence of granules.

  1. Granulocytes: They are leukocytes, with the presence of granules in their cytoplasm. The granulated cells include- eosinophil, basophil, and neutrophil.
  2. Agranulocytes: They are leukocytes, with the absence of granules in their cytoplasm. The a-granulated cells include-monocytes and lymphocytes.

Granulated cells

  • Eosinophil

They are the cells of leukocytes, which are present in the immune system. These cells are responsible for combating infections in parasites of vertebrates and for controlling mechanisms associated with the allergy and asthma. Eosinophil cells are small granulocyte, which is produced in the bone marrow and makes 2 to 4 percent of whole WBCs. These cells are present in high concentrations in the digestive tract.

  • Basophil

They are the least common of the granulocytes, ranging from 0.01to 0.3 percent of WBCs. They contain large cytoplasmic granules, which plays a vital role in mounting a non-specific immune response to pathogens, allergic reactions by releasing histamine and dilates the blood vessels. Around 20 to 25 percent of basophils are present in WBCs. These white blood cells have the ability to be stained when exposed to basic dyes, hence referred to as basophil. These cells are best known for their role in asthma and their result in the inflammation and bronchoconstriction in the airways.

  • Neutrophil

They are normally found in the bloodstream. They are predominant cells, which are present in pus. Around 60 to 70 percent of WBCs are neutrophils with the diameter of 10 to 12 micrometers. The nucleus is 2 to 5 lobed and cytoplasm has very fine granules. Neutrophil helps in the destruction of bacteria with lysosomes and it acts as a strong oxidant. These white blood cells have an ability to stain easily when exposed to neutral dyes, hence referred to as Neutrophil. These blood cells are the first cells of the immune system to respond in response to an invader such as a bacteria or a virus. The lifespan of these WBCs are only for eight hours and are produced every day in the bone marrow.

A granulated cells

  • Monocytes

These cells usually have a large bilobed nucleus, with a diameter of 12 to 20 micrometers. The nucleus is generally of half-moon shaped or kidney-shaped and it occupies 3 to 8 percent of WBCs. They are the garbage trucks of the immune system. The most important functions of Monocytes is to migrate into tissues and clean up dead cells, protect against the bloodborne pathogens and they move very quickly to the sites of infections in the tissues. These white blood cells have a single bean-shaped nucleus, hence referred to as Monocytes.

  • Lymphocytes

They play a vital role in producing antibodies. Their size ranges from 8 to 10 micrometers. They are commonly known as natural killer cells. They play an important role in body defense. In an average, a human body contains about 10 to 12 lymphocytes cells. These white blood cells are colorless cells formed in lymphoid tissue, hence referred to as lymphocytes. There are two main types of lymphocytes – B lymphocytes and T lymphocytes. These cells are very important in the immune systems and are responsible for humoral immunity.

Stay tuned with BYJU’s to learn more in detail about White Blood Cells, its functions and its deficiency disorders.

Practise This Question

Deficiency of growth hormone in childhood leads to: