Study Notes on Blood and Its Components
- Blood is a constantly circulating fluid connective tissue, with numerous cells and proteins suspended in it providing the body with nutrition, oxygen and waste removal.
- The average person has about 5liter of blood.
- Blood accounts for 7% of the human body weight.
- It is a slightly alkaline fluid -pH-7.4. pH in arteries is more than in veins.
- Blood volume: - Males: 69ml/kg body wt., Females: 65ml/kg body wt.
- Plasma volume: - Males: 39ml/kg body wt., Females: 40 ml/kg body wt.
- Hemoglobin contents of blood: - Males: 14.5- 16.5mg/100ml of blood, Females :12- 14.5 gm/100ml of blood.
- One gram of haemoglobin can carry 1.34ml oxygen under optimal conditions.
COMPONENTS OF BLOOD
Whole blood has two components:
- BLOOD PLASMA- A watery liquid extracellular matrix that contains dissolved substances.
- FORMED ELEMENTS – These are cells and cell fragments.
- Blood is about 45% formed elements and 55% blood plasma. Normally more than 99% of formed elements are cells named for their red colour RBC- RED BLOOD CELLS, Pale colourless WBCs- WHITE BLOOD CELLS and Platelets occupy less than 1% of formed elements.
- Blood plasma is about 91.5% water and 8.5% solutes, most of which 7% by weight are proteins.
- PLASMA PROTEINS - HEPATOCYTES (liver cells) synthesize most of the plasma proteins, which include ALBUMINS -54% OF PLASMA PROTEINS, GLOBULINS- 38%, and FIBRINOGEN -7%.
- Certain blood cells develop into cells that produce gamma globulins, an important type of globulins. These plasma proteins are also called antibodies or immunoglobulins because they are produced during certain immune responses.
- Besides proteins, other elements in plasma include: -
- Regulatory substances such as enzymes and hormones
- Gases and waste products such as urea, uric acid, creatinine, ammonia and bilirubin.
RBC (RED BLOOD CELLS) OR ERYTHROCYTES
- RBCs contain oxygen-carrying proteins
- A healthy adult male has about 5.4 million red blood cells per microliter of blood, and a healthy female has about 4.8 million.
- RBC are biconcave discs with a diameter of 7-8 m, certain glycolipids in the plasma membrane of RBCs are antigens and account for the various blood groups such as the ABO and RH groups.
- RBCs lack a nucleus and other organelles and can neither reproduce and nor carry on excessive metabolic activities.
- The cytosol of RBCs contains haemoglobin molecules.
- RBCs are highly specialized for their oxygen transport function. Because mature RBCs have no nucleus, all their internal space is available for oxygen transport.
- Because RBCs lack mitochondria and generate ATP anaerobically (without oxygen), they do not use up any of the oxygen they transport.
WBC (WHITE BLOOD CELLS) OR LEUCOCYTES
- The leucocytes are rounded or irregular in shape as they can change their shape. This enables them to squeeze out of blood capillaries into the tissues (diapedesis).
- It is larger than RBCs.
- The number of leucocytes varies from 6000 to 8000mm.
- The ratio of WBC: RBC in our body is 1:600
- LEUCOCYTOSIS- Raise in WBC count (indicate acute bacterial infection).
- Leukaemia- Abnormal increase of WBCs (blood cancer).
- Leukopenia- Fall in WBC count.
- Structure- Consist of Cell Membrane, Nucleus and Cell organelles.
- They are smaller in size.
- Consist of Large rounded nucleus.
- They are non-motile and non-Phagocytic.
- They produce antibodies,
- They help in healing of injuries.
- These are B and T lymphocytes.
- Lymphocytes are 20 to 25% of leucocytes.
- They are the largest.
- The nucleus is bean-shaped.
- They are motile and phagocytic in nature.
- They change into macrophages after entering tissue spaces.
- It is generally 2 to 10% of leucocytes.
- The nucleus is two lobed.
- They have course granules that take acidic strains (e.g., eosin)
- Their number increases in people with allergic conditions such as asthma or hay fever.
- They help in dissolving blood clot.
- They are non – phagocytic.
- Can attach themselves to parasitic forms and cause their destruction by liberating lysosomal enzymes on their surface.
- 2-3% of leucocytes.
- The nucleus is three lobes.
- They have less number of course granules that take the basic strain. (e.g., methylene blue) strongly
- Basophils release heparin, serotonin and histamine.
- They are generally least in number 0-1%.
- The nucleus is many lobed.
- They consist of fine granules that stain Weakley with both acidic and basic stains.
- They are most numerous.
- Certain neutrophils in female mammals possess a small spherical lobe attached to their nucleus by a stalk called drum stick or Barr body.
- Drumstick is formed by the transformation of X-Chromosomes. They eat harmful germs and are, therefore, phagocytic in nature.
- They are 60-65% of leucocytes.
PLATELETS OR THROMBOCYTES
- Platelets are flat and non-nucleated fragments of cells.
- They are simply bits of protoplasm, bounded by a membrane and contain a few cell organelles and secretory granules in the cytoplasm.
- They are rounded and oval disc-like bodies.
- They are 2-3 micrometres in diameter.
- Blood normally contains 1,50,000- 3.50,000mm3 platelets of blood
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