Blood | Types, Composition, Functions & More


Blood is the medium in which resolved nutrients, gasses, hormones and squanders are delivered all through the body. The clout (weight) of the blood is 1/12th of our body weight.

Components of Blood

It is equipped with two Components;

1.➥ Blood Plasma.

2.➥ Blood cells (B.Cs)  and cell-like structure.

      Blood Plasma

      It is a fluid part of blood. In a typical person blood plasma frames about 55% by volume of absolute blood and cells or cell-like bodies about 45% by volume of the blood.


      Plasma is principally water in which proteins, salts, nutrients and wastes are broken down. Plasma comprises of 90% of water and 10% broke down substances. Most of them broke down substances are kept up at a constant or almost constant level, however different substances change in their fixation. The broke up substances are;

      Inorganic ions or mineral ions

      These are 0.9% of plasma, more than two-thirds of this sum is NaCl (ordinary table salt). Even if the absolute gathering of broken down substances continues as before, change in the centralization of a specific ion can make genuine distractions. The typical pH of human blood is 7.4, which is kept up between narrow limits because the adjustment in pH would influence the chemical reactions of the body.

      Plasma proteins

      It establishes 7 – 9% by weight of the plasma and achieves various functions. The greatest part (almost all)  of these proteins are synthesized in the liver.

      • A portion of the globulins, known as Immunoglobulins or antibodies are delivered in response to antigens, by lymphocytes; and over and above that, are passed to plasma and lymph.
      • The proteins like prothrombin act as a catalyst in the blood coagulating process.
      • Fibrinogen partakes in the blood clotting process.
      • Immunoglobulins play a significant role in the body’s defenses against illnesses.

      Organic nutrients

      This incorporate glucose, fats, phospholipids, amino acids, lactic acids and cholesterol.
      Approximately of them get into (enter) the blood from the intestine (by absorption). Lactic acid created in muscles on account of glycolysis is transferred by the blood to the liver.

      Cholesterol is a salient ingredient; it is metabolized to somewhat, but in addition, works as an antecedent of steroid hormones.

      Nitrogenous waste products

      These incorporate urea and little quantities of uric acid. These are shaped as a result of cellular metabolism in the liver and carried/conveyed from the liver to the organs from where they are expelled i.e. kidneys.


      All hormones are transported by blood, so they are available in blood plasma.


      These incorporate CO₂ and O₂ found in blood plasma in the soluble shape.


      These form 45% by volume of the blood and are of three types;

      1.➥ Red Blood Cells (Erythrocytes).

      2.➥ White Blood Cells (Leucocytes).

      3.➥ Platelets.

        Red Blood Cells (Erythrocytes)


        These are the most umpteen cells in the blood. One cubic millimeter blood of male contains 5 to 5.5 million red blood cells (R.B.Cs) but the female’s blood contains 4 to 4.5 million red blood cells (R.B.Cs) per cubic millimeter.


        At the time of arrangement, they contain nucleus but in mammals, they lost their nucleus before to enter the bloodstream.


        • In embryonic conditions, they are made from liver and spleen.
        • In matures, they are created in the red bone marrow of short bones, for example, sternum, ribs and vertebrae. The mature/adult red blood cells do not separate


        These are biconcave in shape and have an elastic cell membrane.


        Regarding 95% of cytoplasm in red blood cells (R.B.Cs) is the red pigment known as hemoglobin and the remaining 5% consists of enzymes, salts and other proteins.

        Life Span

        The normal life period of R.B.Cs is 4 months (120 days), after which they break down in the liver and spleen and partially by phagocytes by phagocytosis.

        “Around 2 – 10 million red blood cells are formed and ruined every second in normal man”.

        Function of RBCs

        The fundamental function of red blood cells is to transport O₂ and CO₂ to the body.

        White Blood Cells (Leucocytes)


        These are less than R.B.Cs one cubic millimeter blood contains 7000 to 8000 W.B.Cs. These are bigger than R.B.Cs.


        These are boring as they contain no pigment. These are nucleated.


        These are at least five distinct sorts and isolated into two groups based on the shape of the nucleus and density of granules in the cytoplasm.

        1.➥ Granulocytes.
        2.➥ Agranulocytes.


          • The leucocytes, which take over (possess) the lobed nucleus and granular cytoplasm. Their nucleus is specifically 2 to 4% lobed.
          • These are composed in the red bone marrow.
          • These comprise around 71 to 72% of absolute white blood cells.


          These incorporate; neutrophils, eosinophils and basophils.


          The leucocytes, which have clear cytoplasm and single huge & circular nucleus. These are around 28 to 29% of complete white blood cells.


          These incorporate; monocytes and lymphocytes (B and T).


          These are shaped in the lymph node, spleen, tonsils, adenoids, and thymus.

          Life Span

          Monocytes persist from 10 – 20 hours in the blood, and after that enter the tissue and become tissue macrophages, performing phagocytic activities.

          Lymphocytes have a life span of months or even years, but this is contingent on the body’s need for these cells.

          Feature                                          Granulocytes                                       Agranulocytes

          Cell features                              Granular cytoplasm                                      Clear cytoplasm

          Cytoplasmic granules           Present, seeable on staining                        Absent

          Formation                                  Red bone-marrow                                         Lymphoid tissue

          Nucleus                                        Multi-lobed                                                    Single

          Types                                             Eosinophils, basophils, neutrophils         Monocytes, 



          Eosinophils: Kill parasites break inflammatory substances.

          Basophils: Prevent blood clotting.

          Neutrophils: Destroy little particles by phagocytosis.


          Monocytes:    produce macrophages that engulf germs.

          Lymphocytes: produce antibodies and finish germs.


          Functions of WBCs

            • Leucocytes protect the body against foreign invaders.

            • Macrophages (monocytes) and neutrophils travel via vessels. They achieve the site of the injury where bacteria have attacked. Macrophages and neutrophils die during fighting with bacteria and accumulate as pus at the infection site.

            • Basophils produce substance heparin, a substance that inhibits blood clotting.
            • These likewise produce chemicals such as histamine, that take part in allergic reactions in response to tissue damage and microbial in the invasion.

            • Lymphocytes help to create immunity against diseases.

            Plates (Thrombocytes)

            These are not cells but are fragments of enormous cells called megakaryocytes.

            Enucleated, Pigments

            These have no nucleus and no pigment.


            • Platelets help in the transformation of soluble plasma protein fibrinogen into an insoluble structure, fibrin.
            • The fibrin threads entangle red blood cells and different platelets in the area of damaged tissue and form a blood clot.
            • The clot works as a temporary seal to stop bleeding from the injury until the damaged tissue can be repaired.

            Function Of Blood

            1. Maintaining of Osmotic Pressure

            The plasma proteins maintain colloid osmotic pressure of the blood (75% by albumins, 25% by globulins and almost none by fibrinogen).

            2. Transport of Material

            Blood transports of materials, in the body including nutrients, water, salts, and waste products.

            3. Transportation of Hormones

            All hormones are transported by the blood from endocrine tissues to target cells.

            4. Transportation of Gases

            Blood helps in the transport/motion of respiratory gases i.e. O₂ & CO₂.

            5. Defense of Body

            Blood helps in body defenses against diseases.

            6. Destruction of Micro-organisms

            Neutrophils and monocytes engulf and destroy invading microorganisms and toxins of the invaders, e.g. bacteria.

            7. Act as Buffer

            Blood acts as a buffer to keep up the acid-base balance i.e. assiduousness of H⁺ and OH⁻ ions in the body.

            8. Immunity

            Lymphocytes provide immunity by producing antibodies.

            9. Interferon & Antitoxins

            Blood produces interferon and antitoxins, which are proteins and protects our body from nucleic acids and toxins of the invaders.

            10. Maintaining of Body Temperature

            It helps in maintaining the body temperature, cons of water and salts thus help in homeostasis.

            11. Exchange of Material 

            Blood helps in the exchange of materials between blood and body tissue through blood capillaries via the interstitial fluid. 

            12. Homeostasis

            Blood helps the body in maintaining the internal environment by producing heparin, histamines and also maintaining the number of chemicals (water, salts) in the body and maintains body temperature to a constant or nearly constant level.

            13. Blood Clotting

            It helps in the body clotting process and seals the wounds that stop the entry of pathogens in the body.

            Comparison of Different Types of Blood Cells

            (A) ➥ Red Blood cell (Erythrocytes) 


            Biconcave disc without nucleus Approximately μm in diameter.


            Av no present

            5,000,000 per mm³.

            Major Function

            Transports oxygen and a small amount of carbon dioxide.

            (B)➥ White Blood cell (Leucocytes)



            Av No Present

            7500 per mm.³

            Major Function


            (a) Granulocytes

            1. Neutrophil



            About twice the size of red cells, nucleus two to five-lobed.

            Av No Present

            62% of white cells.

            Major Function

            Destroys small paticles by phagocytosis.

            2. Eosinophil


            About twice the size of red cells, nucleus bilobed.

            Av No Present

            2% of white cells.

            Major Function

            Inactivates inflammation producing substances; attacks parasites.

            3. Basophil


            About twice the size of red cells nucleus bilobed.

            Av No Present

            Less than 1% of white  cells.

            Major Function

            Releases heparin to prevent blood clots and histamine, which causes inflammation.

            (b) Agranulocytes

            1. Monocyte


            Tow to three times larger than red cells, nuclear shape from round to lobed.

            Av No Present

            3% of white cells.

            Major Function

            Gives rise to macrophage, which destroys larger particle by phagocytosis.

            2. Lymphocyte


            Slightly large than a red cell, nucleus nearly fills cells.

            Av No Present

            32% of white cells.

            Major Function

            Functions in the immune response by producing antibodies.

            (C)➥ Platelet


            Membrane-bounded cytoplasmic fragment of cells in the bone marrow known as megakaryocytes.

            Av No Present

            250,000 per mm³.

            Major Function

            Involved in blood clotting.

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