Abstract
The porous nature of biological membranes is frequently described by means of a model of equivalent pores. The model assumes a membrane containing an array of uniform cylindri- cal pores and relates the membrane permeability, P, hydraulic conductivity, L,, and reflection coefficient, cr, to the dimensions of the pores and dimensions of the molecules transferred.
The pore dimensions are characterized by the pore radius, Y, and by the pore area per unit path length, A/Ax. (In the placenta P and Lp are measured as products with the surface area of the placental barrier, S. The measured quantities are thus PS and LpS.)