Blood: Biology PSC Notes

Blood: Biology PSC Notes

Blood is the life-sustaining fluid that circulates throughout the body carrying oxygen and other nutrients for the proper functioning of the entire human body.

An interesting fact about the blood is that it can act both as a fluid and as a tissue.

In the blood, there are cells that can perform particular functions which makes it act as a tissue and these cells in turn are held together in a liquid matrix (plasma) and that explains the fluid aspect of the blood.


Basic Facts

  • Epithet – Red River of Life.
  • Study of Blood – Hematology.
  • Study of Blood Vessels & Lymphatics – Angiology.
  • Blood Circulation was discovered by – William Harvey.
  • Amount of blood in a healthy person – 5-6 Liters (varies depending on gender).
  • Normal blood pressure of an adult – 120/80 mm Hg (120 systolic pressure, 80 Diastolic pressure).      (PSC Question: LD Clerk, 2021)
  • pH value of Blood – 7.4 (Alkaline).
  • Viscosity of Blood – 4.7.
  • The instrument used to measure blood pressure – Sphygmomanometer (Inventor Karl Samuel Ritter von Basch, 1881).
  • Color of Blood – Red.
    • The red color of the blood is due to the presence of the iron content pigment called Hemoglobin (also known as a respiratory pigment, b'coz it helps in the transportation of Oxygen).
        • The protein part of Hemoglobin – Globin.
  • Colored connective tissue – Blood.
    • Colorless connective tissue – Lymph.
  • Formation of blood cells are known as – Hemopoiesis.
  • Tissues in the form of liquid in the human body – Blood.
  • Blood proteins are secreted by – Liver.
    • Examples of blood proteins are – Albumin, Globulin & Fibrinogen.
        • Blood protein which acts as antibodies – Globulin.
        • Blood protein which helps in blood clotting – Fibrinogen.
        • Blood protein which controls blood pressure – Albumin.

Components of Blood

The main components of Blood are Plasma, Platelets & Fat Globules. While Plasma is the dominant component, the rest are lipids (fats), electrolytes, water, proteins, and glucose.
Components of Blood


The clear pale yellow liquid portion of the blood is known as Plasma.

  • Level of plasma in the blood is – 55%
  • Percentage of water in plasma – 90%
  • Proteins present in Plasma
    • Albumin – helps in maintaining blood pressure.
    • Globulin – produces antibodies.
    • Fibrinogen – helps in blood clotting.
Plasma is further divided into:
  1. Red Blood Corpuscles (RBC) or Erythrocytes
    • Produced in – Bone marrow.
    • The lifespan of RBC – 120 Days.
    • Biconcave Disk Shaped Cells with a flattened center.
    • Production is controlled by – Erythropoietin (a hormone produced by Kidney).
    • Presence of special protein, Hemoglobin.
    • Blood cells without nuclei.
      • The only mammal having a nucleus in RBC – Camel.
    • 1 ml of blood contains approx. 45-60 lakh RBCs.
    • The Organ that is known as Graveyard of RBC – Spleen.
      • The Organ that is known as the Blood bank in the body (Reservoir of blood) Spleen.
    • Deficiency of RBC causes – Anemia.
    • An abnormal increase in the RBC count known as – Polycythemia.
    • A genetic disease that causes the RBC to lose its shape – Sickle Cell Anemia.

  2. White Blood Corpuscles (WBC) Or Leucocytes
    • Produced at – Spleen, Lymph glands,& bone marrow.
    • The lifespan of WBC – 15 Days.
    • Largest blood cell.
    • Blood cells without any color.
      White Blood Corpuscles (WBC) Or Leucocytes
    • Produces antibodies.
    • 1 ml of blood contains approx. 3700-10000 WBCs.
    • Overproduction of WBC causes – Leukemia.
    • Deficiency of WBC causes the disease – Leukopenia.
    • Types of WBC – 5
      1. Lymphocytes – Smallest WBC.
      2. Monocyte – Largest WBC.
      3. Eosinophils.
      4. Basophils.
      5. Neutrophils (granulocytes).
    The proportion of RBC and WBC in the human body – 5000:1.

    Lymphocytes are further classified into 2. They are:     (PSC Question: LD Clerk, 2021)

    1. B lymphocytes (B cells)  – found in the bone marrow and make antibodies.
    2. T lymphocytes (T cells)  – found in the bone marrow and helps to kill tumor/cancer cells and help control immune responses.

  3. Platelets
    • Produced in – Bone marrow.
    • The lifespan of Platelets – 4-7 Days.
    • The blood cells without any nucleus or color.
    • Helps in the clotting of blood.
    • 1 ml of blood contains approx. 2.5-3.5 Lakh platelets.
    • Process of blood clotting in wounds is called – Coagulation.
    • The normal time for blood clotting – 3-8 Minutes.
      • The enzyme which helps in blood clotting – Thrombokinase.
      • A mineral which helps in blood clotting – Calcium.
      • Protein which helps in blood clotting – Fibrinogen.
    • Blood plasma without clotting factor – Serum.
    • Clotting of blood in blood vessels is called – Thrombosis.
    • The inability of clotting of blood is called – Haemophilia.
      • Hereditary disease.
      • Also known as Christmas Disease, The Royal Disease.
    • An anticoagulant in the blood that prevents coagulation in blood vessels – Heparin.
      • Heparin is produced by – Basophil.
Order of count of different blood cells – RBC > Platelets > WBC

Sometimes the fat accumulation in the blood can result in the blockage of the blood vessel, particularly around the femur bones. Such a condition is called Fat Embolism.

What are the Functions of Blood?

  • Fights infections.
  • Provides nourishment.
  • Gives immunity to the body.
  • Regulates heat and pH levels.
  • Supplies oxygen to all the cells and tissues.
  • Transports hormones, electrolytes, vitamins & antibodies.
  • Carries carbon dioxide (CO₂) and other waste materials to the lungs, kidneys, and digestive system to be removed.

How many Blood Groups/Blood Types are there?

  • Blood groups and Rh factor are discovered by – Karl Landsteiner (1900).
    • Nobel Prize in 1930 for the discovery of blood groups.
  • Rh factor was first discovered in – Rhesus Monkeys.

8 groups [4 Main Groups (+ Rh group)]

  • 4 Main Groups – A, B, O & AB.
      • Most common blood group – O +ve.
      • Rarest blood group – AB -ve.
      • Blood group which is known as the universal donor – O.
      • Blood group which is known as the universal recipient – AB.
      • Blood with Rh antigen is considered as – +ve group.
      • Blood group without antigen – O.
      • Blood group without antibody – AB.
  • Blood Group H / Bombay Group
    • Rare Blood Group.
    • Discovered by – Dr.Y. M. Bhende (1952).
  • Disorder caused by incompatibility between maternal and fetal blood groups – Erythroblastosis Fetalis.

What is Artificial Blood / Blood Surrogate?

  • A substitute that can fulfill some of the functions of the biological blood.
  • Two types
      • Hemoglobin-based oxygen carriers (HBOCs)
      • Perfluorocarbons (PFCs)
  • Examples of artificial blood – Hemopure & PolyHeme.
  • First recognized artificial blood group is – Hemopure.

What are the most common diseases that affect the Blood?

  • Anemia,
  • Hemophilia,
  • Hemorrhage,
  • Leukemia,
  • Leukopenia,
  • Lymphoma,
  • Polycythemia,
  • Sickle Cell Anemia,
  • High Blood pressure (Hypertension) Silent killer,
  • Hemochromatosis Excess amounts of Iron in the blood,
  • Hematoma – Internal bleeding that causes the blood to get collected inside the body tissues,
  • Myocardial infarction – also known as heart attack, occurs when a sudden blood clot develops in one of the coronary arteries, which supply blood to the heart.
      • Block in the artery is removed by Angioplasty.

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📝 SideNotes:

  • World Hemophilia Day – April 17.
  • World Blood Donation Day – June 14.
  • A mercury-filled glass tube for measuring pulses, a forerunner to sphygmomanometer was invented by – Jules Harrison (1835).
  • Color of Blood in Molluscs is – Blue.
  • Substances that resisting our body from disease-causing organisms Antibodies.
  • Substances which are capable of stimulating the formation of antibodies Antigen.
  • During the sleeping time, blood pressure Decrease.
  • Blood bank was invented by – Charles Richard Drew.
  • The chemical substance (anticoagulant) used in blood bank – Sodium Citrate.