The blood as internal environment of the body

Starting to get acquainted with the main participants of the Symphony of life with the features of various systems of the body, we first consider the role of the internal environment of the body - blood. The value of the blood for the life of the human body is enormous. The blood transports to all parts of the body with oxygen, nutrients, removes waste products of metabolism (sometimes harmful metabolites, as they call all the chemical compounds that occur during metabolism); it contains substances that affect the activities of the different organs, helps us to fight with microbes. It was the blood along with the nervous system serves as a unifying factor of the body. If the nerves can be compared with the Telegraph wires, blood vessels, to some extent, such thoroughfares. In other words, the nervous system unites all cells and tissues of organizational, and blood is what unites them, so to speak, economic.
Only the body has 5-6 liters of blood - 1 /13 body weight. It consists of liquid plasma and floating in it blood cells, called shaped elements. Their three categories: red blood cells (erythrocytes), white cells (leukocytesand platelets. Blood cells take 40-42 % of blood volume.