Although blood looks like a single red fluid, it is actually a mixture of different components, each with its own important job. Understanding these parts helps explain why doctors often transfuse specific components (like red cells or platelets) instead of whole blood.

Plasma – the liquid base

Plasma is the clear, straw‑coloured liquid that makes up about 55% of total blood volume. It is mostly water, but it also contains:

·       Proteins such as albumin, clotting factors and antibodies.

·       Salts (electrolytes) like sodium, potassium, calcium and chloride.

·       Nutrients, hormones and waste products.

Plasma keeps blood cells floating and moving through blood vessels. It helps maintain blood pressure, carries proteins that fight infection and clotting factors that help stop bleeding. When plasma is separated from a donation and frozen, it is called fresh frozen plasma (FFP) and can be used to treat certain bleeding disorders or liver problems.

Red blood cells (RBCs) – the oxygen carriers

Red cells give blood its red colour. They are packed with a protein called hemoglobin, which binds oxygen in the lungs and releases it to tissues. Red cells have a flexible, disc‑like shape that lets them squeeze through very small capillaries to reach every part of the body.

If someone does not have enough healthy red cells (a condition called anemia), they may feel tired, short of breath, dizzy, or have pale skin. Severe anemia, or sudden blood loss, can be dangerous because vital organs do not receive enough oxygen. In such cases, transfusions of red cell concentrates from donors can restore oxygen‑carrying capacity.

White blood cells (WBCs) – the defenders

White cells are fewer in number than red cells, but they are essential for fighting infections. There are several types, including neutrophils, lymphocytes and others, each with specialized roles. Together they:

·       Recognize and attack germs (bacteria, viruses, fungi, parasites).

·       Remove damaged or dead cells.

·       Coordinate immune responses and memory against future infections.

People with very low white cell counts, such as some cancer patients receiving chemotherapy, are at high risk of serious infections. While white cells themselves are rarely transfused as standard therapy, the rest of the blood system (including platelets and red cells) is often supported during intensive treatments.

Platelets – the “first responders” for bleeding

Platelets are small cell fragments that rush to the site of vessel injury. When a blood vessel is damaged, platelets:

1.      Stick to the damaged area.

2.     Clump together.

3.     Release chemicals that activate clotting proteins in the plasma.

This process forms a stable blood clot that helps stop bleeding. People with low platelets (thrombocytopenia) or platelets that do not function properly can bruise easily, bleed from gums or nose, or have dangerous internal bleeding. Platelet transfusions from donors are often used for these patients, especially in cancer treatment or bone marrow failure.

Whole blood vs. components

Modern blood banking usually separates each donation into its components: red cells, plasma and sometimes platelets and other products. This allows each patient to receive exactly what they need:

·       Red cell units for anemia and blood loss.

·       Platelet units for bleeding due to low platelets.

·       Plasma for clotting factor deficiencies or massive bleeding.

One whole‑blood donation can therefore help multiple patients, making the best use of each donor’s gift.