ABSTRACT
The cell is a fascinating organism. It is surrounded by a thin and partly permeable wall called a membrane, which provides protection. The cell maintains selective contact with its environment by giving off and absorbing matter. It exchanges heat, nutrients, oxygen, catabolic products and information with its external environment. In the primeval sea the fluid surrounding the cell was infinite. Human cells also live in a liquid environment. However, the volume of that liquid is less than the volume of the cell itself.The reason that the cell environment is not converted into a poisonous brew killing all life is due to the regulatory function performed by the blood supply. The body is constantly taking in water and nutrients and metabolic end products are eliminated through the bowels and the bladder. Such a “maintenance regime” requires specialized organs consisting of specialized cells.
