The fibrous structure of paper is modelled, defining an homogeneised curvature of the pores at the boundaries with the fibres. The ellipticals functions: the ellipse in case of a two-dimensional analysis and the triaxial ellipsoid in case of a three dimensional analysis fit well for this modelling. Stereometric image analysis, high resolution X-ray microtomography, light scattering and light diffraction on paper sheets replicas make possible these models to be materialized. Applications are made for the study of the physical properties of paper particularly: the mechanicals parameters such as paper elasticity, the stress at break, the permeability for the flow of fluids, all properties depending of the anisotropy of the paper fibrous texture. Emphasis is made on the two dimensional properties of the paper sheet which made this material universally dedicated for the development of the humans activities.