Blood - Notes, Biology | General Awareness - Bank Exams PDF Download

Blood

Blood, a vital fluid, is composed of plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets, each playing a crucial role in maintaining bodily functions like oxygen transport, immune defense, and blood clotting. It is a fluid connective tissue. It is 6.8 litres in man and 500 ml less in woman. It is 6 - 8% of body weight (pH 7.4).

Constituents

1. Plasma

What it is: The liquid component of blood, making up about 55% of its volume. 

What it contains: Water, electrolytes, nutrients, hormones, proteins (including clotting factors, antibodies, and albumin), and waste products. 

Function: Serves as a transport medium for blood cells, nutrients, hormones, and waste products. 

2. Red Blood Cells (RBCs) / Erythrocytes

What they are: Specialized cells responsible for carrying oxygen from the lungs to the body's tissues and transporting carbon dioxide back to the lungs. 

What they contain: Hemoglobin, a protein that binds to oxygen. 

Function: Oxygen transport and carbon dioxide removal. 

3. White Blood Cells (WBCs) / Leukocytes

What they are: Cells of the immune system that defend the body against infections and foreign substances. 

Types: Neutrophils, lymphocytes, monocytes, eosinophils, and basophils. 

Function: Immune response, fighting infections, and eliminating foreign invaders. 

4. Platelets / Thrombocytes:

What they are: Small, irregularly shaped cell fragments that play a critical role in blood clotting.

Function: Initiate and participate in the formation of blood clots to stop bleeding. 

Red Blood Corpuscles (RBC)

•  It is also called Erythrocytes, disc - shaped (for increased Surface Area), no nucleus contains a pigment called Haemoglobin, which gives blood its Red Color.
• Average Man : Amount of Haemoglobin is 14 - 15.6 gm / 100 cc of blood (11 - 14 in woman).
• RBCs are produced in spleen and liver in foetus and in bone marrow after birth @ 1.2 million/sec.
• Life of RBC is 120 days after which they are broken down in spleen or liver.
• Product of breakdown of haemoglobin is a pigment (yellow colour), called bilirubin which is normally disposed off through bile whereas haem transferred to red bone marrow. Retention of bilirubin leads to jaundice.
• No. of RBCs is 4.5 - 5 million/cubic mm of blood.
• At high altitude, RBCs increase in number.
• More : Polycythemia. Less: Anaemia

White Blood Corpuscles (WBC)

•  It is also called  Leucocytes, rounded, with a nucleus, far less numerous than RBCs (1 : 400 - 500) (5,000 - 10,000 /cu mm), life 3 – 4 days, soldiers of body's defence system.

• 2 Types : Granulocytes (Basophils, Eosinophils, Neutrophils) and Agranulocytes (Monocytes, Lymphocytes)
• Basophils : Take up basic stains. Have an S-shaped nucleus. Secrete an anti - coagulant Heparin, which prevents clots within the blood vessels.
• Eosinophils or Acidophils : Take up acidic stains. Assists in defence mechanism.
• Neutrophils : Stain equally well with both acidic and basic dyes. Most numerous of the WBCs (65 - 70%).
• Monocytes : Largest of all. Very motile.
• Lymphocytes : 25% of the WBC. Takes part in antigen and antibody formation. 

Platelets

•  It is also called Thrombocytes, formed in bone marrow, about 250,000 / cu mm of blood,
• life 3 - 7 days, sets off blood clotting.

Plasma (65%)

• Watery part of blood, clear, yellow fluid.
• Contains about 90% water, proteins and organic salts.
• Plasma contains 7% proteins which include Albumin, Globulin and Fibrinogen.
• Plasma transports nutrients from the small intestine to the body tissues, and return the waste material to the kidneys, where it is filtered out.
• The protein in plasma includes antibodies also, to assist in defence mechanism.
• Regulates pH of blood.
• Approx. 60% blood is water only.

Lymph

• Lymph = Blood - RBC, i.e., Plasma + WBC.
• Lymph forms second circulatory system. It acts as middle man between blood and tissue.
• All interchanges of nutrients and waste products between blood and tissue takes place through lymph only.
• It has more of lymphocytes as compared to that of blood (Blood has more of neutrophils).
• Spleen produces lymph. At the same time it also acts as the graveyard of lymph.
• Spleen is also known by the name of 'Blood Bank' because RBCs, WBCs and Lymph are produced in spleen.
• It is situated above left kidney behind the stomach.
• Spleen produces lymph. At the same time it also acts as the graveyard of lymph.
• Spleen is also known by the name of 'Blood Bank' because RBCs, WBCs and Lymph are produced in spleen.
• It is situated above left kidney behind the stomach.

Blood Groupings

• Karl Landsteiner (Australian pathologist). He discovered A, B and O blood groups in 1900.
• Decastello and Sturle in 1902 discovered AB blood group.
• ABO system of blood groups is based on antigens and antibodies.
• Antigens: They are proteins and are found on the surface of RBCs. 
• Antigens are A and B.
• Antibodies: They are produced in lymph glands and are present in blood plasma.

• Antibodies are a and b.
• AB: Universal recipient
• O: Universal donor
• RH Factor: It is based on Rh antigen.
• Discovered in 1940 by Landsteiner and A.S. Veiner.
• It discovered in Rhesus monkey.
• A person can be Rh+ or Rh-.
• Rh+ can receive blood from Rh- but no vice - versa.