  We show that the parton distribution functions (PDF) described by the
statistical model have very interesting physical properties which help to
understand the structure of partons. The role of the quark helicity components
is emphasized as they represent the building blocks of the PDF. In the model
the sign of the polarized quarks PDF comes out in a quite natural way once the
thermodynamical potentials with a given helicity are known. Introducing the
concept of entropy we study the states madeof |2u + d >, |u +d +s > and $|2\bar
u +\bar d >$, for a fixed Q^2, the variation with x shows that the first state
has a dominant entropy due to the effect of u quark. We prove that the PDF
parameters obtained from experiments give in fact an optimal solution of an
entropy equation subject to constraints. We develop a new approach of the
polarized gluon density based on a neural model which explains its property, in
particular, a large positivity value and an agreement with the positvity
constraint. An extension of this neural approach is applied to quarks giving a
coherent description of the partons structure.
