Our human body's first line of defence against diseases, bacteria, or any foreign material is white blood cells. White blood cells, which are also called leukocytes, are cells of our immune system that protect our bodies. White blood cells are present throughout our blood and lymphatic system. The count of white blood cells in the body indicates the presence of disease in the body.
Leukocytes can be divided into several categories. Based on structure, these are divided into granulocytes and agranulocytes. On the basis of cell lineage, these are divided into two categories - myeloid cells or lymphoid cells. Further classification of white blood cells on the basis of their functional and structural characteristics gives us - neutrophils, eosinophils, basophils, lymphocytes and monocytes.
The classification as the name suggests is based upon certain structural features. Granulocytes are present in the cytoplasm in the form of granules whereas agranulocytes are present without the granules. Furthermore, granulocytes have four lobes, whereas agranulocytes are only single lobed. We will further discuss the point of difference between granulocytes and agranulocytes in detail in this module.
White blood cells act as soldiers of the body that work against any foreign invaders or carriers of the disease. Based on the structural differences, we categorise leukocytes into granulocytes and agranulocytes. All white blood cells have nucleus present in them, unlike the red blood cells and platelets.
Granulocytes and agranulocytes have certain structural features that differentiate them. Before understanding the critical point of difference between both of them, let us discuss each of them in detail.
Granulocytes have specific granules present in their cytoplasm. The nucleus present in granulocytes is lobed into three segments. The most abundant granulocytes are neutrophils. Others are eosinophils, basophils and mast cells. These are present in the innate immune system.
Neutrophils - Neutrophils are the most abundant white blood cells. They defend the body against any bacterial or fungal infection and are usually the first responders.
Eosinophils - Eosinophils have kidney-shaped lobed nuclei. They primarily defend against parasitic infections but also help against allergies and collagen diseases.
Basophils - Basophils are one of the least abundant white blood cells present. Their primary function is allergic or antigen response. They secrete chemicals, histamine and heparin, which dilate the blood vessels and make them more permeable to help the body's defence.
Mast cells- Mast cells are present in tissues and protect against pathogens and allergic reactions.
Agranulocytes are white blood cells with no granules in their cytoplasm. These have a single lobe present in the nucleus. Lymphocytes and monocytes are agranulocytes present in the human body:
Lymphocytes- Lymphocytes are predominantly present in the lymphatic system than in the blood. It has B-cells that make antibodies, T-cells and natural killer cells.
Monocytes- The role of monocytes is to help and share the function of neutrophils. They work like vacuum cleaners and live a longer life. Another crucial part of monocytes is to provide T-cells with pieces of pathogens so that they can be recognised and killed again in future.
Granulocytes and agranulocytes are two broad categories of white blood cells present in the human body. They have some structural differences between them, like the presence or absence of granules in their cytoplasm. Granulocytes and agranulocytes have different and specified functions.
The points of difference between granulocytes and agranulocytes are given below.
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1. What are the Different Types of White Blood Cells?
Ans: White blood cells form our body's immune system which protects us from infectious disease and foreign pathogens. Several types of white blood cells are present in our body and protect us as given in the following.
Neutrophils- These are the first responders against any microbial infection. They exist in two forms- neutrophil killers and neutrophil cagers. These are the most abundant white blood cells.
Eosinophils- They protect us from parasitic infections, allergies and disease of the spleen and nervous system. Eosinophils secrete chemicals over the parasites to destroy them.
Basophils- Basophils primarily work as an allergic or antigen response system. It aids the other white blood cells by releasing chemicals, histamine, which dilates the blood vessels and heparin that increases them more permeable.
Lymphocytes- These are commonly present in the lymphatic system. B-cells, T-cells and natural killers protect us against pathogens.
Monocytes- Monocytes present the pathogens to T-cells for recognition.
2. Explain the Different Classifications of Leukocytes.
Ans: Leukocytes or white blood cells are present in the body to protect us from harmful and infectious diseases. These diseases can be caused due to infections, bacterias, parasites etc. White blood cells protect us from these deadly diseases. They can be classified into several categories based upon:
On the Basis of Structure
Granulocytes- granulocytes are white blood cells with multiple lobes in their nuclei and granules in its cytoplasm.
Agranulocytes- They have a single lobed nucleus, but there are no granules in its cytoplasm,
On the Basis of Lineage
Based on the Type of White Blood Cells
Neutrophils-Primary responders and most abundant white blood cells
Eosinophils- Primary function against parasitic infections
Basophils- Secretes chemicals that dilate the blood vessels and increase their permeability
Lymphocytes- Commonly present in lymphatic systems. B-cells, T-cells and natural killers which attack pathogens.
Monocytes- presents pathogen pieces to T-cells for recognition and action against them in the future.