Unit 1: The organisation of the human body                    1   2   3   4   5

3. Cell variety and differentiation

The human body has enormous amount of cells. The exactly number is unknown, but it is estimated that it is closed to 70 millions of millions.

Although all cells of our body have a similar structure, they are non identical.

There are differences among them about shape, size, functions, etc.

It seems that exist almost 250 kinds of cells in the human body.

Characteristics of each cell type depend on their function, the tissue that they form part and the cells around it.

When a person develops and grows, cells divide and rise in number. In addition these cells change and take a particular characteristics about shape, size, organelles, etc., which make them especially able to do a particular function. This process is called cellular differentiation or specialisation.

3.1. What is the reason for the enormous variety of cellular types

in the human body?

3.2. Is it possible to see a human ovule with the naked eye?

        And a spermatozoid?