Blood definition can be as the red fluid in the body that contains white and red blood cells, platelets, proteins, and other elements which is transported throughout the body by the circulatory system.
Blood circulates throughout the body through a network of muscular blood vessels, called arteries and veins. Blood is pumped continuously by the heart through these blood vessels. They carry blood to each and every cell of the body, which number in billions. This is extremely essential because blood carries various nutrients to the cells essential for them to function. They also carry waste products like CO2, urea and other such materials from various cells to lungs, kidneys and other organs of the body which help in flushing these out of the body.
Without blood, we would not be able to keep our bodies warm or cool down as the situation demanded. We would not be able to stave off infections. We would not even be able to get our nutrients to various parts of the body or throw out waste products.