Blood may be described as a red liquid that flows through a network of arteries and veins in all vertebrates and is essential for life. Basically, there are three types of blood cells - red blood cells (RBC), white blood cells (leukocytes) and platelets. While the red blood cells enclose a substance known as hemoglobin and also transport oxygen to the tissues, the platelets that are created in the bone marrow are essential for formation of blood clots. In addition, blood is made up of water, numerous diverse types of proteins, inclusive of antibodies, crucial hormones and transport molecules, nourishing substances like fats, sugars and amino acids and most essentially, living cells. In fact, all the three blood cells are produced in the bone marrow and they develop from a cell called hematopoietic stem cell. It may be noted here that the deadly disease leukemia is a cancer caused by the abnormal development of the white blood cells.
Plasma is a placid dilute liquid belonging to a group of compounds that maintain the resistance of capillary walls to infiltration and pressure altercations in humans. Plasma does not contain any cell, but is utilized as a prop up device for numerous cells that remain floating in it. Nevertheless, plasma is just not a carrier of cells, but encloses several substances like proteins (antibodies and albumin that are essential for the thickening of blood), glucose, vital minerals (sodium, calcium, potassium, chlorine and others), soluble fats (triglycerides and cholesterol) as well as numerous substances that are produced during organic activities (lactic acid, urea, creatine and others) that ascertain the appropriate performance of our body.
Forms of blood cells
- Red blood cells
- The red blood cells, a main constituent of blood, resemble tiny sacs that are plane at the center. These cells do not possess any nucleus and their main purpose is to carry hemoglobin to the different parts of the body. Hemoglobin, in turn, provides oxygen collected from the lungs to the different body parts. Precisely speaking, while passing through the arteries, the red blood cells dispense oxygen to all the organs of our body, including the heart, brain and muscles. Simultaneously, the red blood cells take away carbon dioxide (CO2) from the organs it supplies oxygen and carry it back to the lungs traveling through the veins.
The red blood cells have a vivid red color when they travel through the arteries containing oxygen and while they are carrying carbon dioxide to the lungs through the veins, their color change to blue. This is the primary reason why blood appears bright red when traveling through arteries and bluish while passing through the veins. Our bloodstream contains an extremely high number of red blood cells - around five million every cubic millimeter of blood. The usual lifetime of the red blood cells is around 120 days and, like any other cells of the blood, they are produced in the bone marrow.
The red blood cells present in the blood are extremely cautious since when number diminishes, it also reduces the amount of hemoglobin carried by them and this may lead to an ailment called anemia. There are several reasons for developing anemia and the most widespread cause is loss of blood either through any secondary hemorrhage owing to an injury, heavy menstruation, giving birth and intestinal flow of blood. In addition, insufficiency of vitamins like vitamin B12 and folic acid as well as iron may result in anemia. In specific instances, anemia may also be an indication of a caution of more grave maladies that result in the decline in the body's capability of producing adequate red blood cells in the bloodstream. Some of these cases include leukemia, aplasia and lymphoma.
Apparently, the red blood cells transport antigens (a substance that is able to encourage the production of antibodies) of the ABO (presence of antigens A, B, both, or neither) and Rh blood categories.
- White blood cells
- The white blood cells or leukocytes are genuine cells since they contain all the features of a normal cell - a nucleus, cytoplasm (in space in a cell) as well as a cell membrane. The nucleus of a cell may have different forms, for instance, it may be disc-shaped and composed of a solitary hemisphere or part or alternately comprise a number of lobes and seem to be as many. The cytoplasm or the intracellular space encloses enzymes that are essential to absorb alien bodies. The cell membrane holds HLA (H denoting human, L denoting leucocytes and the A denoting antigens) tissue clusters that characterize every human being. The HLA tissues perform a crucial role in transplant rejection effects.
Basically, the leukocytes or white blood cells have two big families known as lymphocytes and myelocytes. These two categories of white blood cells are characterized by means of their nucleus as well as the color of their cytoplasm or the intracellular space of these leukocytes.
- This category of white blood cells makes up approximately 55 to 65 per cent of all the leukocytes. Researchers initially were of the view that the myelocyte cells enclosed numerous nuclei and hence, also called them 'polynuclears'. However, presently we are aware that these cells possess only a single nucleus that is made up of numerous parts or hemispheres that are connected to each other by means of an arrangement of delicate filaments. The cytoplasm or intracellular space of myelocytes encloses small particles or granules that single out pigments and confront reddish or bluish shades. The other smaller independent particles in the cytoplasm or corpuscles derive their other name 'granulocytes' from these granules. The hue of these grain can be distinguished as neutrophilic (somewhat bluish) polynuclears, basophilic (deep bluish) polynuclears and eosinophilic (reddish) polynuclears.
The myelocytes or 'polynuclears' are responsible for performing a number of important tasks in our body. The neutrophilic polynuclears that are slightly bluish hued are focused in the digestion of bacteria and have a crucial function in fighting contagions. Under normal circumstances, neutrophilic polynuclears are present in reasonable numbers, but they enhance numerically when there is any infection in the body. On the other hand, the eosinophilic polynuclears that have a reddish shade have an important task to perform in fighting allergic effects as well as strengthening the immune system to fight parasites. It may be mentioned here that the terms polynuclears and granulocytes are perfect and they are generally made use of to delegate the different categories of myelocytes.
- On the other hand, the lymphocytes present in the white blood cells comprise the remaining portion of leukocytes - approximately 35 to 45 per cent. The lymphocytes possess big and elliptical or oval-shaped nucleus, but do not enclose any granules. Basically, the lymph modes produce these blood cells. They have a crucial function in combating contagions and transplant rejections as these blood cells are focused on the production of antibodies. It is common knowledge that the antibodies are responsible for raiding viruses, bacteria as well as other alien bodies. While putting of successive contagions, these blood cells are also capable of retaining information regarding several viruses. This particular trend or occurrence is generally called immunization.
- Platelets present in the blood appear as microscopic sacs and have asymmetrical forms. These colorless substances have a sticky surface that enables them to attach to one another forming blood clots. Basically, blood clots block the walls of the arteries and veins, thereby putting off blood outflow or hemorrhages. The platelets too have a vital function, as when their numbers in the blood decline, the individual becomes vulnerable to bruising as well as blood outflow from the body (hemorrhages).