Q.Name the components of the formed elements in the blood and mention one major function of each of them.

The formed elements are the cellular part of blood, making up close to 45 per cent of its volume. They are of three kinds:

• Erythrocytes (red blood cells): carry the respiratory gases, since they are packed with the iron-containing protein haemoglobin.
• Leucocytes (white blood cells): defend the body — some engulf and destroy invading organisms, while others drive the immune responses.
• Platelets (thrombocytes): bring about the coagulation, or clotting, of blood.

When we speak of blood as a tissue, part of what we mean is that it contains living cells suspended in its fluid matrix. These cells and cell fragments are together called the formed elements, and they account for close to 45 per cent of the blood by volume. There are three of them, each shaped for a very different job.

The erythrocytes, or red blood cells, are by far the most numerous cells in blood. They are biconcave, usually lack a nucleus when mature, and are filled with haemoglobin, a red, iron-containing protein. This haemoglobin is what allows them to perform their central role — the transport of respiratory gases around the body.

The leucocytes, or white blood cells, are colourless because they carry no haemoglobin, and they are nucleated and far fewer in number. Their business is defence. Some of them, such as neutrophils and monocytes, are phagocytic and engulf foreign organisms that enter the body, while lymphocytes carry out the body's immune responses.

The platelets, also called thrombocytes, are not whole cells but fragments budded off from large cells in the bone marrow. They release substances that are chiefly involved in the coagulation, or clotting, of blood; when their numbers fall too low, the blood cannot clot properly and heavy bleeding can follow.

Method: Naming and Functionally Classifying Blood's Formed Elements

Use this approach for any "name and describe" question about the cellular components of blood.

Steps

Step 1: Separate the fluid part from the cellular part first

Before listing anything, remember blood has two broad parts — plasma (the fluid matrix) and formed elements (the cells/cell fragments suspended in it). This stops you from accidentally including plasma proteins when the question asks only about formed elements.

Step 2: List the three formed elements with their one defining structural feature

Name erythrocytes, leucocytes and platelets, and immediately pair each with the single feature that makes it recognisable — erythrocytes are haemoglobin-filled, leucocytes are nucleated defenders, platelets are cell fragments (not whole cells).

Step 3: Attach one function to each type by matching structure to job

Haemoglobin content points to gas transport; the ability to engulf invaders or mount immune responses points to defence; the fragment's role in releasing clotting substances points to coagulation. Never state a function without tying it back to the structural feature that explains it.

Step 4 (Applying to related questions): This same name → structural feature → function chain works for any question that names or describes blood cell types, including an MCQ asking which cell performs a given job.