Human Blood And Their Composition


Blood is a liquid connective tissue, human blood delivered some necessary substances like nutrients and oxygen to the cells. And transports waste products form cells to away from our body. It has two main Blood components: plasma & cells (Red blood cells, White blood cells and Platelets). Plasma, which constitutes 55% of blood fluid, is mostly water (92%) and contains proteins, glucose, mineral ions, hormones, carbon dioxide. Albumin is the main protein in plasma(7%), and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are mainly RBCs or erythrocytes 4.7 to 6.1 million (males) 4.2 to 5.4 million (females), WBCs or leukocytes 4000 – 11000 and platelets or thrombocytes 1,50,000 – 500,000.

Physical properties of blood

  • Blood is slightly alkaline fluid because Ph of blood is 7.35 to 7.45.
  • An average adult has a blood volume approximately 5 liter,which composes about 8% of the total body weight.
  • Osmolarity of blood is 275 to 295 mmol/kg.
  • Specific gravity of blood is 1.052 to 1.062.
  • Blood temperature is 38°c or 100.°f.
  • Blood is made of 45% cells and 55% plasma.

Functions of blood in body –

  • Supply of oxygen to tissues
  • Supply the nutrients such as glucose, amino acids, and fatty acids.
  • Removal of waste such as carbon dioxide, urea, and lactic acid etc.
  • Immunological functions, including circulation of white blood cells, and detection of foreign body material by antibodies.
  • Coagulation, the response to a broken blood vessel, the conversion of blood from a liquid to a semisolid gel to stop bleeding.
  • Messenger functions, including the transport of hormones and the signaling of tissue damage.
  • Regulation of core body temperature.
  • Hydraulic functions.

Components of blood

There are two components of blood.
(1) plasma (2) cells

Blood Plasma

plasma is the straw color liquid component of blood, in which blood cells are suspended,plasma made 55% part of blood.plasma is made of water, salts and proteins. Proteins present in plasma called plasma protein, plasma proteins are responsible for osmotic pressure of blood.

blood transfusion complication precautions

composition of plasma

(1) 90% water (2) 8% protein (3) Inorganic salts (4) 1.1%organic salt

plasma proteins –

  • Albumin
  • Globulin
  • Fibrinogen

Inorganic salts –

  • Sodium 135 to 146 mM
  • Potassium 3.5 to 5.2 mM
  • Calcium 2.1 to 2.7 mM
  • Carbonate 23 to 31 mM.
  • Phosphate 0.7 to 1.4

Blood Cells and its Functions –

There are three type of cells presents in blood. That are (1) RBC / ERYTHROCYTES (2) WBC / LEUKOCYTES (3) PLATELETS

RBC / ERYTHROCYTES 4.7 to 6.1 million (males) 4.2 to 5.4 million (females) –

  • RBC also called erythrocyte, red color of blood is due to red blood cells because RBC contains heamoglobin, one RBC contains 280 million Hb molecule.
  • heamoglobin is a red iron rich protein that binds oxygen. red color of Hb is due to prophyrin pigment. 1 gm Hb contain 3.34 mg iron.
  • Mature RBC is small, round and biconcave in shape.
  • Nucleus absent in RBC.
  • RBC covered by a membrane composed of lipid and proteins.
  • Diameter of RBC is 7.2 µm.
  • Normal life span of RBC is 120 days.
  • RBC develops in bone marrow in adulthood and in embryonic life RBC develops in yolk sac and in fetal life RBC develops mainly in spleen, liver and thymus.
  • It destroy in spleen, so the spleen is called grave yard of RBC.
  • Normal RBC count is 4.7 to 6.1 mcl, and normal count in children- 4.0 to 5.5 mcl.
  • Production of RBC is called erythropoisis, kidney hormone erythropoitin helps in production of RBC.

WBC / LEUKOCYTES  4000 – 11000 –

WBC is also called leukocyte. Nucleus present in WBC, dead WBC called pus. life span of WBC is depends on their work and demand. WBC further divided in two groups. (1) Granular leukocyte (2)  Agranular leukocyte. WBCs concentration is decrease below the lower limit is called leukemia.

(1) Granular leukocyte –

Granules presents in the cytoplasm of granulocytes, granules have enzyme (ex. proteases) which destroy the microorganism. three granulocytes present in WBC are following.

  • Eosinophil – diameter of eosinophil is 10 to 14 µm. it seems red orange color after stain with acidic dye (eosin), eosinophil play important role in allergy and parasitic infection ex. malaria.
  • Basophil – Diameter of basophil is 8 to 10 µm, it seems blue purple color after stain with basic dye (methylene blue). Play important role in healing process.
  • Neutrophil – Diameter of neutrophil is 10 to 12 µm, it seems violet color after stain with both dye (eosin+methylene blue=leishman’s stain). It provides first line defense. Old neutrophil called polymorphonuclear leukocyte, because its nucleus have 2-5 lobes and the young neutrophil called bands because its nucleus seems like a Rod.

(2) Agranular leukocytes –

Lymphocyte –

Diameter of lymphocyte is 7 to 12µm. Lymphocyte divided in two types according to work and formation. (i)T lymphocyte (ii)B lymphocyte.

(i)T lymphocyte – Its final maturation held in thymus gland so it called T lymphocyte. T-lymphocytes are responsible for cellular immunity. T lymphocyte divided in four cells these are following –

  • Helper T cells or CD4+ or inducer T cells– During any infection helper T cells stimulates other cells, normal count of CD4+ cells are 500 to 1500 cells/mm3 (average 950 mm3). if CD4+ count decrease below 200 mm3 than it indicates AIDS.
  • Cytotoxic T cells or killer cells or CD8+ cells– These cells attacks directly to microorganism during infection.
  • Suppress T lymphocyte – These cells decreases activity of killer cells.
  • Memory T lymphocyte – These cells presents in lymphoid tissue, these cells prevents same infection in future.

(ii) B lymphocyte – Its final maturation held in Bone marrow (after birth) and during fetal life it mature in liver so these cells called B lymphocyte. B lymphocyte responsible for Humoral immunity or B cells immunity. Humoral immunity means immunity that produce from antibody and immunoglobulin. B lymphocyte divided in two groups are-

A. Plasma cells- Plasma cells produce 5 types of immunoglobulin or antibody.

  • IgA – IgA presents in breast milk, sweat, tear and saliva.
  • IgG – IgG is most common type of immunoglobulin, it founds approximately 80%. IgG only can cross placenta, it indicates chronic infection.
  • IgM – After any infection plasma cells secrets first IgM, it indicates acute infection.
  • IgE – It involves in allergic and hypersensitivity.
  • IgD – it is less in numbers and less important.

Monocyte –

It’s diameter is 14 to 18µm. It is largest WBC cells. Monocyte migrates blood to tissue and produce macrophage. Macrophages divided in two type.
Fixed Macrophage and Wandering Macrophage.

Fixed macrophage – Some macrophages stay fixed in any special tissue. Ex- kupffer cells in Liver and alveolar cells in Lungs.
Wandering marophage – These macrophage are movable in one to another organ, so called wandering macrophage.

Platelets or Thrombocytes  1,50,000 – 500,000 –

  • Low platelet concentration is Thrombocytopenia.
  • Elevated platelet concentration is Thrombocytosis.
  • Thrombocytes are not a complete cells, it develops from dividation of a megakaryocyte in to 2000 to 3000 parts.
  • Platelets are colorless and disc shaped cells.
  • Platelet do not have Nucleus.
  • Diameter is 2 to 4µm and its volume is 7.5 cubic micron (µm3).
  • Platelets are responsible for control blood loss from damaged blood vessels. By formation of a clot within an intact vessel.
  • Thrombocytes have three important properties-1.Adhesiveness 2. Aggregation 3. Agglutination.
    Its life span is 5 to 9 days.
  • Dead platelets or thrombocytes are destroyed by fixed macrophages in Liver and Spleen.