Question

describe the appearence and relative abundance of each type of leukocytes

Answer 1

Introduction:

Blood is the only liquid connective tissue of our body and is widely distributed across the body parts. Around 5-5.5 liters of blood is present in the human body and it is slightly alkaline.

Blood performs a diverse range of functions like;

a) Transportation of gases like oxygen and carbon dioxide

b) Transportation of hormones

c) Transportation of absorbed nutrients

d) Mediating antigen and antibody reactions helping in the elimination of the pathogens

Blood composition:

Blood is majorly made of two components namely; Plasma and the formed elements

Plasma: It comprises approximately 70% of the total blood. It is pale yellow in color and is a clear transparent fluid which majorly is made of water (90-92%) and remaining 8% components are the dissolved solids like mineral salts, nutrients, antibodies and many others.

Formed elements: These are the different types of the blood cells. They are the erythrocytes (Red Blood cells) and the Leucocytes (white blood cells)

Leucocytes:

They are also called as the white blood cells as they do not have hemoglobin. The total number of leucocytes is somewhere around 4-11* 103 /mm3 of blood in humans and this is also called as the total leucocyte count.

A rise in this number is called as Leucocytosis. An abnormal increase in the total WBC count is called as Leukemia (also called as blood cancer). Similarly, a fall in the WBC count is called as Leucopenia.

Classification of Leucocytes:

Classification of leucocytes is done on the basis of the presence or absence of the granules present in them and also thus their ability to take up the stains. They are classified as below:

a) Granulocyte: These are those types of WBCs which have coarse granules in their cytoplasm and thus can readily take up a stain. Their life span is around 4-8 hours in the blood and 4-5 days in the body tissues. Depending on the nature of the stain they take up, they are further classified as;

1. Eosinophils: Their nucleus has two lobes and the granules present in the cytoplasm of cell takes up an acidic stain named eosin. Their usual number is known to increase during severe allergic conditions commonly called as Eosinophilia and hence they seem to play a very important role in the immune system.

2. Basophils: The nucleus of these cells is three lobed. The coarse granules present in the cytoplasm takes up the basic stain like methylene blue. They probably feature and action like mast cells and thus releases chemicals like histamine, and heparin thus mediating vasoconstriction and vasodilation.

3. Neutrophils: The nucleus of these cells has many lobes. They are called neutrophils because the coarse granules present in them can take up both acidic as well as basic stains.

b) Agranulocyte: These are those types of WBCs which does not have coarse granules in their cell’s cytoplasm and hence they do not take up any stain. Their life span may vary from 10-20 hours to even some years depending on their types. They are classified as below:

1. Lymphocyte: These are the cells with less cytoplasm and a large rounded nucleus. There are two types of lymphocytes;

B lymphocytes: also called as plasma cells. They synthesize antibodies and thus help in facilitating the antigen elimination.

T lymphocytes: They are the antigen presenting cells. Depending on the antigen type; they are of two sub types. If an antigen is of foreign origin, they are called T helper cells whereas if an antigen is of indigenous origin, they are called T cytotoxic cells.

2. Monocytes: These are the largest type of the cells amongst all the different leucocytes. They later get transformed into macrophages and are meant to perform phagocytosis thereby eliminating the foreign pathogens.

Thus, these were the different types of the leucocytes (WBCs) found in the blood of humans. Given below is a DLC (differential leukocyte count) present within the human blood and also summarizing the different leukocyte count.

Leukocyte	Percentage
Neutrophils	40-70%
Lymphocytes	20-40%
Monocytes	2-10%
Eosinophils	1-6%
Basophils	0-1%