Preface

Excerpt

Biological transport across cellular structures is of great importance to many tissues and organs including the mammary gland. Epithelia are principal cellular barriers that can form single or multiple layers lining the internal and external surfaces of organs. Epithelial cells interact with two external environments, one at each side of the cell, which come in contact with different fluids. This unique arrangement allows epithelial cells to transport components selectively from one side of the epithelial cells to the other surface under specific endocrine and other forms of control. The mammary gland secretory cells are luminal epithelial cells that provide the barrier between components originating from the blood that are transported or secreted by the cells. As a consequence, certain blood constituents can reach much higher concentrations in milk than in blood during defined functional stages of the mammary gland while others are prohibited from leaving the blood circulation. …