The human body is an amazing living machine, made up of tens of thousands of billions of cells. These billions of cells are divided into some 200 different types, sizes and shapes according to their function: skin cells, hair cells, blood cells, tooth enamel or dentine, bone cells, etc. Their size varies from about 7 micrometres (7 thousandths of a millimetre) for a red blood cell, to over 30 micrometres for other types of cells. Cells that make up the nervous system can be larger because of prolongations (dendrites) that transmit nerve impulses.
The shape of these cells is directly linked to their function. For example, red blood cells have a smooth, regular shape enabling them to circulate easily in the blood flow. Muscle cells have a long, cylindrical shape so they slide against each together when the muscle contracts. Similarly, the prolongations of nerve cells help accelerate the body’s nerve impulses.
These billions of cells, classified into different types, each with a well-defined, specialised function, continually interact and cooperate with each other throughout the body.
This is why you can listen to classical music while driving a car, why you can solve a maths problem while digesting, and why you can digest while sleeping. All these tasks are being carried out as you breathe and as your blood flows at 37°C through your veins.
For any voluntary or involuntary activity to take place, and to uphold this continual miracle of life inside your body, your cells need energy. They also need energy to divide, thereby replacing defective cells, maintaining the body’s “eternal youth”.
We will have the opportunity to talk about it in the coming articles.