Q.(a) Mention the functions of

When you think about what blood actually does, it helps to picture it as a team where every member has a clearly assigned role. The cells of blood are not all-purpose; each type has its own specialised function, and the health of the body depends on all of them doing their part.

The red blood cells are the carriers. They contain haemoglobin, an iron-containing protein, and their central job is the transport of respiratory gases around the body. Without them, oxygen could not be moved efficiently from the lungs to the tissues.

The white blood cells are the defenders, but they defend in different ways. Neutrophils and monocytes are phagocytic — they engulf and destroy foreign organisms that get into the body. Basophils secrete substances such as histamine, serotonin and heparin and take part in inflammatory reactions. Eosinophils resist infections and are also linked with allergic reactions. Lymphocytes, which come in two forms called B and T, are responsible for the body's immune responses.

The platelets are the repair crew. They release substances that are involved in the coagulation, or clotting, of blood, so that an injured vessel can be sealed. If platelet numbers fall too low, clotting fails and a person can lose too much blood. …