What is blood made of?

Blood is a specialized body fluid that is made of four main components: red blood cells, white blood cells, plasma, and platelets. 

1. The most abundant cells in the blood, red blood cells (RBCs) account for about 40% to 45% of the total volume. RBCs in humans are anucleate and shaped like a bi-concave disk with a flattened center. They contain a special protein known as hemoglobin, which helps transport oxygen from the lungs to the rest of the body and carbon dioxide from the body to the lungs. Hemoglobin also gives red blood cells their red color. 
2. White Blood Cells or Leukocytes are an integral part of the immune system and are responsible for protecting the body from infection. They make up only about 1% of the total blood volume. There are two main types of white blood cells – neutrophils, which are the ‘immediate response’ WBCs and lymphocytes, which work in various ways to eliminate pathogens and fight infection.  
3. Plasma is the liquid component of the blood. It contains a mixture of water, proteins, sugar, salts, and fat. The plasma is responsible for transporting blood cells to all parts of the body along with nutrients, antibodies, chemical proteins such as hormones, clotting proteins, and waste products. 
4. Platelets or Thrombocytes are rather small cell fragments that are involved in coagulation or the blood clotting process. They accumulate at the injury site and stick the linking of the injured blood vessel, creating a platform that supports blood coagulation and facilitates the formation of a fibrin clot that covers the wound, prevents blood leakage, and promotes healing.