Different White Blood Cells And Their Functions

Different White Blood Cells And Their Functions – Blood cells, also called hematopoietic cells, hemocytes, or hematocytes, are specialized cells found in the blood of mammals including humans. They are produced in the bone marrow through a process known as hematopoiesis.

Blood cells are broadly classified into three types: 1) red blood cells (RBCs), 2) white blood cells (WBCs), and 3) platelets, which together make up 45% of the total blood volume.

Different White Blood Cells And Their Functions

Structure: A typical mammalian red blood cell is biconcave disk-shaped and compressed in the middle with a diameter of about 6.2-8.2 µm. A cross-sectional view of an RBC looks like a dumbbell.

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Quantity: They are the most abundant of all circulating blood cells, accounting for 40 to 45 percent of the total blood volume.

Composition: They are rich in hemoglobin, an iron-containing protein that binds oxygen and gives it its red color. Nucleus and many other organelles are absent from RBCs.

Abundance: Found throughout the body including connective tissue, the bloodstream, and the lymphatic system. It makes up only 1% of the total blood volume.

In general, WBCs are classified into five types: Neutrophils (Granulocytes), Eosinophils (Granulocytes), Basophils (Granulocytes), Lymphocytes (Agranulocytes), and Monocytes (Agranulocytes).

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Besides these general functions, there are specific functions performed by each of the five types of WBCs.

Abundance: It is present in less than 1% of the total blood cell count. Platelets are about 1/10 to 1/20 as numerous as white blood cells.

Ans. RBCs, WBCs, and Platelets make up about 45% of the total blood volume, and the remaining 55% is made up of plasma, the liquid part of the blood.

Ans. Platelets are the smallest of all blood cells, accounting for less than 1% of the total blood cell count.

What Is The Function Of Red Blood Cells?

Ans. The lymph nodes and spleen produce T cells and B cells, a type of white blood called lymphocytes. The leukocyte, also known as the white blood cell (WBC), is the main part of the body’s defense against disease. Leukocytes protect the body from invading microorganisms and body cells with altered DNA, and clean up waste. Platelets are essential for the repair of blood vessels when damage has occurred; they also provide growth factors for healing and repair. See Chapter 18.3 Erythrocytes for an overview of leukocytes and platelets.

Although leukocytes and erythrocytes both originate from hematopoietic stem cells in the bone marrow, they are very different from each other in several important ways. For example, leukocytes are much more numerous than erythrocytes: Normally there are only 5000 to 10,000

L. They are also larger than erythrocytes and are the only structures that are complete cells, with a nucleus and organelles. And although there is only one type of erythrocyte, there are many types of leukocytes. Most of these types have a much shorter life span than that of erythrocytes, some as short as a few hours or a few minutes in the case of an acute infection.

One of the best features of leukocytes is their mobility. While erythrocytes spend their days circulating within the blood vessels, leukocytes often leave the blood stream to perform their protective functions in the body’s tissues. For leukocytes, the vascular network is the highway they travel in and out of to reach their destination. These cells are sometimes given different names depending on their function, such as macrophage or microglia. As shown in Figure 18.4.1, they leave capillaries – tiny blood vessels – or other small vessels through a process known as migration (from the Latin “removal”) or diapedesis (dia- = “through”; -pedan = “jumping”) where they squeeze the cells around the blood vessel.

What Are The Functions Of Human Red Blood Cells?

After leaving the capillaries, some leukocytes will take up stable positions in the lymphatic tissue, bone marrow, spleen, thymus, or other organs. Others will move through the gaps of flesh much like amoebas, continually expanding their plasma membranes, sometimes wandering freely, and sometimes moving in the direction where they are attracted by chemical signals. This attraction of leukocytes occurs due to good chemotaxis (literally “movement in response to chemicals”), something that happens where injured or infected cells and nearby leukocytes release a chemical equivalent of “emergency” call, attracting more leukocytes to the site. In clinical medicine, the different numbers of types and percentages of leukocytes present are often the main indicators in making a diagnosis and choosing a treatment.

Figure 18.4.1 – Migration: The leukocyte leaves the blood vessel and then moves through the connective tissue of the dermis to the wound site. Some leukocytes, such as eosinophil and neutrophil, are characterized as granular leukocytes. They release chemicals from their granules that kill bacteria; they are also capable of phagocytosis. The monocyte, an agranular leukocyte, differentiates into a macrophage which then phagocytizes the pathogens.

When scientists began to look at blood slides, it soon became clear that leukocytes can be divided into two groups, according to the fact that their cytoplasm contains visible granules:

We will consider granular leukocytes in order from the most common to the smallest. All of these are produced in the red marrow and have a short life of hours to days. They usually have a lobed nucleus and are classified according to the color of their granules (Figure 18.4.2).

What Are Different Types Of Lymphocytes? Write Their Function?

Figure 18.4.2 – Granular Leukocytes: The neutrophil has small particles that stain light lilac and a nucleus with two to five lobes. The eosinophil’s granules are slightly larger and have a red-orange color, and its nucleus has two to three lobes. The basophil has large granules that stain blue to purple and a double-sided nucleus.

The most common of all leukocytes, neutrophils will comprise 50-70 percent of the total leukocyte count. Children 10–12

M in size, much larger than erythrocytes. They are called neutrophils because their granules show up more clearly with chemically neutral (neither acidic nor basic) stains. Granules are numerous but fine and usually appear light lacy. The nucleus has a distinctive lobed appearance and can have two to five lobes, the number increasing with the age of the cell. Older neutrophils have an increased number of lobes and are often called polymorphonuclear (nucleus with many shapes), or simply “polys.” Smaller and smaller neutrophils begin to develop lobes and are known as “bands”.

Neutrophils react quickly to the site of infection and are active phagocytes by selecting bacteria. Their granules contain lysozyme, an enzyme capable of breaking down, or breaking down, bacterial cell walls; oxidants such as hydrogen peroxide; and defensins, proteins that bind and penetrate bacterial and fungal plasma membranes, so that the contents of the cells can escape. Abnormally high numbers of neutrophils indicate infection and/or inflammation, especially caused by bacteria, but are also found in burn patients and others with unusual stress. Burn injury increases the proliferation of neutrophils to fight infection that can be caused by the destruction of the skin barrier. Low numbers can be caused by drug toxicity and other disorders, and can increase a person’s risk of infection.

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M wide. The granules of eosinophils stain strongly with an acidic stain known as eosin. The nucleus of the eosinophil will have two to three lobes and, if properly purified, the granules will have a clear red to orange color.

Granules of eosinophils include antihistamine molecules, which oppose the actions of histamines, inflammatory chemicals produced by basophils and mast cells. Some eosinophil granules contain molecules that are toxic to parasitic worms, which can enter the body through the integument, or when a person eats raw or undercooked fish or meat. Eosinophils are also capable of phagocytosis and are particularly active when antibodies bind to their target and form an antigen-antibody complex. High numbers of eosinophils are common in patients with allergies, parasitic worm infestations, and certain autoimmune diseases. Low numbers may be due to drug toxicity and stress.

Basophils are the most common leukocytes, usually comprising less than one percent of the total leukocyte count. They are slightly smaller than neutrophils and eosinophils at 8-10

M wide. Granules of basophils stain strongly with basic (alkaline) stains. Basophils contain large granules that take a dark green stain and are too common to make it difficult to see the two-lobed nucleus.

Types Of White Blood Cells

Normally, basophils intensify the inflammatory response. They share this characteristic with mast cells. Previously, mast cells were thought of as basophils that leave the circulation. However, this seems to be the case, as the two types of cells develop from different lineages.

The granules of basophils release histamines, which cause inflammation, and heparin, which is against blood clotting. High numbers of basophils are associated with allergies, parasitic infections, and hypothyroidism. Low numbers are associated with pregnancy, stress, and hyperthyroidism.

Agranular leukocytes contain smaller, less visible granules in their cytoplasm than granular leukocytes. The nucleus is simple in shape, sometimes indented but without distinct lobes. There are two main types of agranulocytes: lymphocytes and monocytes (see figure 1; chapter 18.3).

Lymphocytes are the only blood product that originates from lymphoid stem cells. Although they initially occur in the bone marrow, most of their subsequent development and reproduction occur in lymphatic tissue. Lymphocytes are present

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