ABOUT BLOOD

Blood is a vital fluid that sustains life. It transports oxygen and essential nutrients to the body's cells, carries hormones and other substances, and removes carbon dioxide and waste products for elimination.

An average healthy adult has approximately 5–6 litres of blood, accounting for about 7–8% of body weight. Blood consists of a liquid component called plasma and three main cellular components: Red Blood Cells (RBCs), White Blood Cells (WBCs) and Platelets.

BLOOD COMPONENTS

  1. Plasma

Plasma constitutes approximately 55% of blood and is a straw-yellow fluid. It contains water, proteins, electrolytes, nutrients, hormones and clotting factors. Its major proteins include:

  • Albumin: Maintains fluid balance in the bloodstream.
  • Globulins: Help protect the body against infections and support immunity.
  • Fibrinogen: Plays an important role in blood clotting.
  1. Red Blood Cells (RBCs)

Red blood cells contain haemoglobin, an iron-rich protein that carries oxygen from the lungs to body tissues and transports some carbon dioxide back to the lungs for elimination. Haemoglobin levels are an important indicator of health and are routinely assessed in blood donation eligibility.

  1. White Blood Cells (WBCs)

White blood cells are an essential part of the body's immune system. They protect the body against infections by identifying and fighting bacteria, viruses and other harmful organisms.

  1. Platelets

Platelets are small blood components that play a crucial role in blood clotting. They help seal injured blood vessels, control bleeding and support tissue repair.

UNDERSTANDING BLOOD GROUPS

Although blood has the same basic components, it is not identical in everyone. Blood groups are determined by specific antigens present on the surface of red blood cells.

The two most commonly known blood-group classification systems are the ABO system and the Rh system.

The ABO Blood Group System

There are four main blood groups:

  • Group A: Has A antigens on red blood cells and anti-B antibodies in plasma.
  • Group B: Has B antigens on red blood cells and anti-A antibodies in plasma.
  • Group AB: Has both A and B antigens and normally has neither anti-A nor anti-B antibodies.
  • Group O: Has neither A nor B antigens and normally has both anti-A and anti-B antibodies.

The Rh Factor

The Rh factor, particularly the D antigen, further classifies blood as positive (+) or negative (−).

For example, combining the ABO and Rh systems gives eight commonly recognised blood groups:

A+, A−, B+, B−, AB+, AB−, O+ and O−.

Why Is Blood Group Matching Important?

A safe blood transfusion requires careful blood-group testing and compatibility assessment to prevent potentially serious transfusion reactions.

  • O Negative: Generally considered the universal red blood cell donor group in emergency situations.
  • AB Positive: Generally considered the universal red blood cell recipient group.
  • AB Plasma: Generally considered the universal plasma donor group.

However, safe transfusion always requires appropriate compatibility testing and cross-matching, as prescribed by medical protocols.

KNOW YOUR BLOOD GROUP. DONATE BLOOD. SAVE LIVES.