Main Components of the Human Blood

T&E Science Club (c) Stephenie Liew, CC-Zero

Blood is obviously essential to everyone’s living – we can’t live without it. Recently, I’ve had an opportunity to visit CBR, the Centre of Blood Research at UBC on a field trip with my club. We met research scientists and found out what they were doing with blood, which made me wonder about the basics of human blood: what is it made of?

Blood is a highly specialized tissue – it contains over 4,000 components. It accounts for 7-8% of human blood and is in charge of a lot of things. Blood transports oxygen and nourishment to all parts of our bodies while taking away the waste products. It evenly distributes heat, fights invaders, and maintains the homeostasis of water, ions or pH in the body. It has four main components: red blood cells, white blood cells, platelets, and plasma.

Red Blood Cells

Red blood cells are specialized cells that have no nucleus or mitochondria so they have space for a protein named hemoglobin. They account for 40-50% of blood’s total volume, and their main function is to transport oxygen from the lungs and get rid of carbon dioxide.

White Blood Cells & Platelets

There are many sub-units of white blood cells, but they all serve one function, which is to respond to the immune system. Different white blood cells respond in different ways and fix different problems in the human body. These cells are in very small numbers comparing to the RBCs, as they only take around 1% of blood’s volume. White blood cells work with platelets at sites of injuries, as platelets are cell fractions that contain blood clotting chemicals.

T&E Science Club (C) Stephenie Liew, CC-Zero


Plasma is a clear, yellow solution that makes up nearly 55% of blood’s volume. It contains salts, nutrients, proteins, sugar, fat, and water – it is basically the fluid that carries other components. Plasma also contains blood clotting factors, and its main job is to bring nourishment to all parts of the body.

So as a conclusion, the four main components of blood were introduced to you. They include red blood cells, white blood cells, platelets, and plasma. Together, they function in their specialized areas and keep us living.

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