Biology Study Notes on BLOOD


It is a fluid connective tissue. It is 6.8 liters in man and 500 ml less in a woman. Its constitute 6-8% of body weight (pH 7.4).

(i) CONSTITUENTS OF BLOOD
Solid or cellular part called Blood Cells and fluid part called the Blood Plasma. Approx. 60% blood is water only. 
(a)Red blood corpuscles (RBC) (b) White blood corpuscles (WBC) (c) Platelets plasma (65%)  (d)  Lymph (Plasma + WBC).

(a)Red blood corpuscles (RBC)
These are also called Erythrocytes, disc-shaped (for increased surface area). There is no nucleus.
These contain a pigment called Haemoglobin which gives red colour to the blood.Average man: Amount of Haemoglobin is 14-15.6 gm/ 100cc of blood (11 - 14 in woman). 
RBCs are produced in spleen and liver in foetus and in bone marrow after birth @ 1.2 million per sec.
Number of RBCs is 4.5 – 5 million / cubic mm of blood. Life of RBC is 120 days after which they are broken down in spleen or liver. Product of breakdown of hemoglobin is a pigment (yellow colour), called bilirubin which is normally disposed off through bile whereas heme 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: Anemia

(b)White blood corpuscles (WBC)
These are also called Leucocytes, rounded with nucleus. Far less numerous than RBCs (1 : 400-500) (5,000-10,000 /cu mm), life 3-4 days. These are soldiers of body’s defense system. Takes part in antigen and antibody formation.
Helps in blood clotting.

Are of 2 types: 
(i)Granulocytes: Basophils, Eosinophils, Neutrophils 
(ii) 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 defense mechanism. 
Neutrophils: Stain equally well with both acidic and basic dyes: Most numerous of the WBC5 (65-70%). Defense. 
Monocytes: Largest of all. Very motile. Defense. 
Lymphocytes: 25% of the WBC. Takes part in antigen and antibody formation. 
Lymphocytes & phagocytes
Lymphocytes are white blood cells (WBC) while phagocytes are cells that attack and engulf invading microbes. 

(c)Platelets
Also called Thrombocytes, formed in bone marrow, sets off blood clotting.

(d)Plasma (65%)
  • It is the liquid part of the blood. This is clear, yellow fluid. It contains 90% water, proteins, and organic salts. It regulates the pH of blood.
  • It contains 7% proteins which include Albumin, Globulin, and Fibrinogen. The protein in a plasma includes antibodies also, to assist in defense mechanism.
  • Plasma transports nutrients from the small intestine to the body tissues and returns the waste material to the kidneys, where it is filtered out. 
  • Regulates the pH of blood. 
  • Also called Thrombocytes, formed in bone marrow, about 250,000 / cu mm of blood, life 3-7 days, sets off blood clotting. 
  • (e)Lymph  (Plasma + WBC)
  • Lymph = Blood — RBC, i.e., Plasma + WBC. 
Lymph forms a second circulating system. It acts as a middleman between blood and tissue. It has more lymphocytes as compared to that of blood (Blood has more neutrophils). 
All interchanges of nutrients and waste products between blood and tissues take place through lymph only.
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 RBC’s, WBC and lymph are produced in the spleen. It is situated above the left kidney behind the stomach.

(ii)Blood groupings 
  • Father of Blood Grouping: 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.
(Percentage in brackets imply the percentage of the World population of that particular blood group) 
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 the Rhesus monkey. A person can be Rh+ or Rh-. In the world population Rh+ are 85% and Rh - are 15% only. + can receive blood from Rh- but not vice-versa. 
Blood, transfusion technique was first developed by James Blundell in 1825.

No comments