Blood is the body fluid in humans and other animals that delivers the essential materials for life to the body's cells. It has sometimes been called a fluid “tissue,” because like solid tissues it contains several types of cells which perform complex functions for the human body. Blood is a liquid connective tissue made up of blood cells and plasma that circulate inside the blood vessels under the pumping action of the heart. Functions of blood : It transports carbon dioxide from the tissues to the lungs partly in combination with haemoglobin and partly as a solution in blood plasma. It transports digested food to different organs of the body which is utilized by cells. Transport of hormones. Transport of nitrogenous excretory products like ammonia, urea, and uric acid. Blood Basics Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets. The blood that runs through the veins, arteries, and capillaries is known as whole blood —a mixture of about 55% plasma and 45% blood cells. About 7% to 8% of your total body weight is blood . An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about 9 pints.
