One of the most interesting systems of the body is the blood. It is called a system, even though the end product, the fluid blood itself, is totally different to the structural organs that make up most other systems, such as the heart, brain, nerves, intestines and so forth.

Blood (and its many component parts) is the end point of production that takes place in various other fixed manufacturing sites. These are located at key areas around the body.

The blood itself is composed of two parts, a solid or “cellular” component, and a fluid or “humeral” part. If a tube of blood is placed in a perpendicular position and left undisturbed, very soon the cellular component will gradually sink to the lower part of the tube. It is usually a very deep crimson color, almost black to the naked eye. Above this stands the clearer, yellowish-colored fluid, or plasma.

The cellular element consists of an immense number of red and white cells (or corpuscles) and platelets.

The red cells (erythrocytes) appear as round, biconcave discs when examined under the microscope. Viewed sideways, they look a bit like a dumbbell, if you can recall what this looks like. The thin outer envelope contains a cell filled with the chemical hemoglobin.

This is the product that has an extreme affinity for oxygen. When it comes into close contact with oxygen (in the air we inhale into the lungs with each breath), it immediately absorbs it, and turns a brilliant red. This is called oxyhemoglobin.

It is the oxygenated blood that is then returned to the heart to be pumped out into the aorta and into the general arterial blood-vessel system. It is transported to every muscle fibre and organ, and the oxygen combines with other products to form energy, so enabling the muscles and organs to carry out their appointed duties.