Components of Blood and their functions


Blood is essential for good health because the body depends on a steady supply of fuel and oxygen to reach its billions of cells. Even the heart couldn’t survive without blood flowing through the vessels that bring nourishment to its muscular walls. Blood also carries carbon-di-oxide and other waste materials to the lungs, kidneys, and digestive system from there they are removed from the body. 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.

Components of Blood:

Blood is classified as connective tissue and consists of two main components:

1. Plasma: Blood plasma is a liquid component of blood that suspends blood cells and many other substances.

2. Formed Elements: It is made up of blood cells and platelets. The formed elements are so named because they are enclosed in a plasma membrane. It also has a definite structure and shape. All formed elements are cells except for the platelets, which are tiny fragments of bone marrow cells. Formed elements are of three types:

    i. Erythrocytes or RBCs: Red Blood Cells also called erythrocytes. It is a cellular component of blood, millions of which in our circulation give the blood its characteristic color and carry oxygen from the lungs to the tissues. The structure of mature human red blood cells is small, round, and biconcave. It appears dumbell-shaped in the profile. It is covered with a membrane composed of lipids and proteins, lacks a nucleus, and contains hemoglobin – a red, iron-rich protein that binds oxygen.

    ii. Leucocytes or WBCs: White Blood cells are a part of the immune system and help our bodies fight infection. They circulate in the blood so that they can be transported to an area where an infection has developed. In a normal adult body, there are 4000 to 10000 (average 7000) WBCs per microliter of blood. White blood cells are of many different types each having its own particular purpose in the body.

    iii. Platelets: Platelets help the blood to clot by forming something that is called a platelet plug. The other way that blood clots is through coagulation factors. It also helps to promote other blood clotting mechanisms. There are approximately 150000 to 400000 platelets in each microliter of blood (average is 250000).

    Platelets are formed in the bone marrow from very large cells called megakaryocytes. It breaks up into fragments. These cellular fragments are platelets. They don’t have a nucleus and don’t reproduce. Platelets generally last for an average of 10 days. It contains many chemicals that assist clotting.