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Class-11 Biology CHAPTER-

18
BODY FLUIDS AND CffiCULATION

Body fluids are the medium of transport of nutrients, oxygen and other important
substances in the body.
Blood is the most commonly used body fluid in most of the higher organisms. Lymph also

transports certain substances like protein and fats.

Blood

Blood is a fluid connective tissue composed of a fluid matrix, plasma and the blood

corpuscles. It forms about 30-35% of the extracellular fluid. It is slightly alkaline fluid having

pH7.4.

Plasma is straw coloured viscous fluid that constitutes 55% of blood volume. It
consists of 90-92% water, 6-8% protein (fibrinogens, albumins and globulins), glucose,

amino acids and small amount of minerals like Na+, Ca++, er etc.

• Erythrocytes, leucocytes and platelets are collectively called formed elements.

• Erythrocytes are most abundant cells in human body. Total blood count of RBCs is 5-
5.5 million, which is slightly less in females due to menstruation. It is formed in bone

marrow. Nucleus is absent in mammalian RBCs having biconcave shape.

• Every 100 ml of blood contain 12-16gm. of haemoglobin. They have life span of 120
days. They are destroyed in spleen( graveyard of RBCs)

• Leucocytes or WBCsare colourless due to absence of haemoglobin. 6000-8000 of
WBCs are present in each ml. of blood.

• Neutrophils are most abundant and basophils are least abundant WBCs. Monocytes

and neutrophils are phagocytic cells which destroy foreign organisms.
Eosfnophil Neulrophil T lymphocyte
•

Basophil Monocyle B lymphocyte ·

• Basophils secrete histamine, serotonin and heparin that are involved in inflammatory
reactions.

• Eosinophils resist infection and allergic reactions. B and T lymphocytes are
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