What is Blood? Composition and Function of Blood

What is Blood? Definition

BLOOD is a connective tissue. The total volume of blood constitutes approximately 8% of the body weight or 5.6 liters.

Composition of Blood

Composition of Blood

Blood is composed of a straw-coloured fluid like known as plasma and floating in this fluid are different types of cells or corpuscles. The main portions of the blood are mentioned below.

LIQUID PORTION (about 45 - 55% of blood)

a. Plasma: Water - 90 - 92%

b. Plasma Proteins: about 7% comprising of Albumin, Globulin & Fibrinogen.

The remaining 3% is comprising of:

c. Mineral Salts& NaCI, NaHCO3, K, Mg, Ca, etc.

d. Nutrient materials: Amino acids, Vitamins, and Fatty acids.

e. Organic Waste Products: Urea, Uric acid, Creatinine.

f. Hormones & Enzymes.

g. Gases: Oxygen, Carbon dioxide and Nitrogen.

Function of Blood

1. Blood carries oxygen from lungs to tissues.


2. It carries nutrient materials from G.I.tract to tissues.


3. Hormones manufactured in endocrine glands to target organs.


4. Blood carries waste products to excretory organs.


5. Blood gives defense against foreign bodies & microbes by reaching antibodies to sites of infection.


6. It prevents dehydration of tissues.


7. It maintaining body temperature.


8. Blood clotting & healing of wounds