•Cells in all
categories except Type E can divide to make new cells. They are all subject to mutation, cell
damage, oncogenesis and, it is thought by some, are subject to replicative senescence.
•Cells of Type A in the
early embryo progressively differentiate to make all cells of Types B,
C or D.
•All cells of Type D
result from differentiation of cells of Type A, B and/or C, possibly via
intermediary progenitor and stem cell types.
•Some cells of Type B
may differentiate through several intermediate forms before creating
Type D cells. Hierarchy in
differentiation is always preserved under natural conditions, although it may or may not necessarily be the
case that intermediate stem cell types are involved depending on the kind
of cell.
•An early embryo consists of
A-Type cells. This supply-chain process
continues through life although
in aging there will be more and more cells of Types D and E and fewer and fewer active cells of Types B and C.
and virtually no active Type
A cells left.
•Healthy normal aging is
thus a matter or cellular supply chain management. The body must assure that there are not too many Type
E cells around for they
create havoc.
•