Blood is a body fluid that delivers essential substances like nutrients and oxygen to the cells of the body. Blood also transports carbon dioxide and other waste products away from the cells, to the lungs, kidneys, and digestive system; from there they are removed from the body. In addition, the blood also helps fight infection in open cuts in the body.
Our body has billions of cells that need regular supply of fuel and oxygen to function. Blood meets these requirements and ensures proper functioning of cells, thus, also making sure that our body keeps in good health. It might interest you that an average adult human body has about five liters of blood.
Blood in our bodies is pumped by the heart through a network of arteries and veins. It is interesting to note that even the heart cannot survive without blood flowing through the vessels that bring nourishment to its muscular walls.
Having said that, it is anybody’s guess, we can't live without blood. Without blood, we couldn't keep warm or cool off, we couldn't fight infections, and we couldn't get rid of our own waste products.
Blood, therefore, is a vital body fluid – lifeline of a body that performs many important functions.
Functions of Blood
- Blood performs important functions, some of which are as under:-
- Supply of oxygen to cells / tissues
- Supply of nutrients such as glucose, amino acids and fatty acids Removal of waste such as carbon dioxide, urea and lactic acid
- Making body immune by circulation of white cells, and detection of foreign material by antibodies
- Regulation of core body temperature
- Hydraulic functions
- Aiding body's self-repair mechanism by Coagulation
- Messenger functions like transportation of hormones and the signaling of tissue damage
- Regulation of body pH (the normal pH of blood - 7.35 - 7.45)
Composition of Blood
The blood that flows through a network of veins and arteries is called whole blood. Whole blood contains three types of blood cells which are as under:
- Red blood cells (also called RBCs or erythrocytes) – contain iron rich protein called hemoglobin, giving blood its characteristic red color.
- White blood cells (also called WBCs or leukocytes) – help fighting diseases.
- Platelets (also called thrombocytes) – help in blood clotting.
These blood cells are mostly manufactured in the bone marrow, especially in the bone marrow of bones that make up the spine (vertebrae), ribs, pelvis, skull, and breastbone (sternum). Bone marrow is the soft tissue inside our bones.
These cells that make up the whole blood travel through the circulatory system suspended in a yellowish fluid called plasma. Plasma is 90% water and contains nutrients, proteins, hormones, and waste products. Whole blood is a mixture of blood cells and plasma.
In addition to the cells mentioned above, the blood also contains clotting factors and other important substances, such as nutrients from the food that has been processed by the digestive system. Also, the hormones released by endocrine glands are present in the blood which carries them to the body parts that need them.
Blood Clotting – An important mechanism to heal wounds
Blood, in addition to platelets, also contains important proteins called clotting factors. These clotting factors are vital for the process of blood clotting. Although platelets alone can plug leaks in small blood vessels and even temporarily stop / slow down bleeding, the action of clotting factors is needed to produce a strong, stable clot.
Platelets work with clotting factors to form solid lumps that seal leaks, wounds, cuts, and scratches and prevent bleeding inside and on the surfaces of our bodies.
However, when large blood vessels are severed, the body may not be able to repair itself through blood clotting process alone. Dressings or stitches, in addition to body own blood clotting mechanism, are used to help control bleeding in such cases.