Molecular Physiology of Gastrointestinal Function During Development

The mammalian intestinal tract undergoes dramatic changes during the first few weeks of postnatal life. Genetic and neurohormonal regulators influence the changes in digestive and transport functions that mediate the development of the gut. In mammals, the most significant changes occur during the suckling/weaning transition. At birth, the digestive and secretory function of intestines is not fully developed, and thus nutrient absorption occurs throughout the small and large intestines and along the entire length of the crypt-villus axis. During the suckling period, factors from the mother’s milk affect intestinal function and regulate the expression of genes involved in nutrient transport and immune function. After weaning, a different set of physiologic regulators and dietary factors direct rapid functional maturation of the gut epithelium. This chapter reviews the key discoveries that have led to the current understanding of ontogenic maturation of the gastrointestinal function (secretory, digestive, absorptive, and ontogenic regulation).