Biological boundaries and biological age: solutions of variational problems

If we consider the chronologic age of an organism, it is often unable to give useful information about its stage in the development or aging processes. Then we propose here to use a biological age essentially determined by the number of used mitoses before the Hayflick's limit for the tissues of the critical organs (in the sense where their loss causes the death of the whole organism) of a living being. We propose a definition of the biological age of an organ based on the Hayflicks limit and on a desynchronization index (the cell entropy) of its tissues.