Blood is a circulating body fluid that carries oxygen to different parts of the body. Its plasma is composed of more than 90 per cent water. However, why water cannot replace blood in the human circulatory system despite its significant importance in the human body is quite an interesting question, the answer of which leads us to the startling facts.
Blood is an important fluid for the survival of humans. Technically, it is a liquid that is pumped by the heart to all parts of the body via arteries, returned to the heart via veins, and vice versa. Blood is scientifically known to have been composed of two main components: the liquid part- plasma and the solid component- formed elements tissues and blood cells. Therefore, it is the only fluid connective tissue in the human body, comprising 45 per cent of formed elements and 55 per cent of the fluid plasma. Moving to the composition of plasma, it is ninety per cent of the water with the remaining ten per cent of salt, hormones, and lipids. Hence, blood contains all the basic components that are required for human survival.
However, what makes the blood a specialized fluid in the circulatory system of the human body, and can the blood be replaced with water are the doubts still to be cleared. Imagine if water had circulated in our vessels, they would have been known as water vessels instead of blood vessels. Anyways, the answer is simply a big no. Everything is not specialized for everything; yet, everything is specialized for a specialized thing. In the same way, water cannot replace blood in the human body, and humans cannot drink blood at the place of water. Moving to the former, blood contains highly compatible transporting protein- haemoglobin- that not only makes the blood appear red but also carries oxygen to the body.
Haemoglobin is, in fact, an iron-containing protein that mainly transports oxygen from the lungs to the tissues. It forms an unstable bond with oxygen to form bright red oxyhemoglobin, which, then, is reduced to purplish-red haemoglobin on reaching the target tissues. Since haemoglobin develops in the bone marrow blood cells-erythrocytes, it- upon the death of erythrocytes-is broken up, releasing bilirubin- a chemical that is excreted into the bile and gives the faeces a yellow-brown colour- as a by-product.
Hence, blood is an important component of the human body. It is responsible for the transportation of oxygen to all parts of the body from the lungs through a specialized oxygen-binding protein, haemoglobin. Therefore, it is due to the certain characteristics features – above all the presence of haemoglobin- that makes the blood highly specific for its function of transportation of gases salts to the body tissues, thus, making human existence possible on earth. Stating differently, fluids other than the blood cannot transport oxygen in the body because of the absence of haemoglobin.