Components of Closed Circulatory System in Man

The components of the closed circulatory system in man are:

blood

• A fluid that can carry all the materials to be transported ()

heart

• A pumping organ that can push the fluid through the body - as time taken is important ()

blood vessels

• Many tubes through which the fluid can flow through the body ()

Blood

It is a red coloured, viscous, alkaline (pH about 7.4) fluid flowing through the body of higher animals. The adult human body consists of 5-6 litres of blood. It has two components:

• Fluid plasma

• Solid formed elements

The elements include corpuscles and platelets.

Plasma

It forms about 55% of the blood (about 3 litres). Its composition is as follows:

Water (92%)

Soluble components

The soluble components are:

Proteins

(7%) - includes hormones, enzymes, globulin antibodies, albumin and fibrinogen. (Blood plasma without fibrinogen and other clotting factors is called Serum and is a yellow watery fluid).

Nutrients

- include glucose, amino acids, fatty acids and glycerol

Metabolic Substances

- include vitamins, lactic acid, urea and uric acid (non-protein nitrogenous substances - NPN)

Inorganic Ions

(0.9%) - include sodium, potassium, calcium, magnesium, chlorine and radicals like sulphate, phosphate, etc.

Pigments

- include small amounts of bilirubin, carotenes, etc. that give the plasma its characteristic yellow colour.

Functions of Plasma

• Maintains osmotic pressure and viscosity of the blood

• Helps in transport of various substances like the hormones, enzymes, etc.

• Acts as a protein reservoir

• Helps in clotting of blood

• Helps in regulating body temperature