title: The development of the small intestine.
abstract: The remarkable degree of coordination between the development of various aspects of gastrointestinal function suggests that the process may be triggered by a single or a few central mechanisms, such as weaning and (or) hormones. Precocious development of enzyme and transport function can be induced by exogenous thyroxine and corticosteroids, while thyroidectomy and adrenalectomy abolish the normal pattern of postnatal development. These hormones may have a primary or a permissive role. Activation of the dormant hormonal mechanism could be controlled by a genetically coded biologic clock, such as chronologic age, or by a biological signal such as body size and oral intake. Generally speaking, shortly after birth, there are increases in the intestinal mucosal surface area, brush border membrane enzymes, and carrier-mediated transport. These adaptive changes occur as a result of the genetic endowment of the animal, but may be modified by environmental factors, particularly nutrient intake.
mesh_terms: D000375:Aging; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D050260:Carbohydrate Metabolism; D004032:Diet; D004041:Dietary Fats / Q000378:metabolism; D004044:Dietary Proteins / Q000378:metabolism; D004063:Digestion; D004064:Digestive System / Q000254:growth & development; D004068:Digestive System Physiological Phenomena; D004151:Dipeptides / Q000378:metabolism; D005314:Embryonic and Fetal Development; D005823:Genetics; D005938:Glucocorticoids / Q000502:physiology; D006133:Growth Substances / Q000502:physiology; D006728:Hormones / Q000502:physiology; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development* / Q000502:physiology; D046911:Macromolecular Substances; D008871:Microvilli / Q000648:ultrastructure; D008903:Minerals / Q000378:metabolism; D010873:Pinocytosis; D012964:Sodium / Q000378:metabolism; D013963:Thyroid Hormones / Q000502:physiology; D014815:Vitamins / Q000378:metabolism; D014886:Weaning
chemical_list: D000596:Amino Acids; D004041:Dietary Fats; D004044:Dietary Proteins; D004151:Dipeptides; D005938:Glucocorticoids; D006133:Growth Substances; D006728:Hormones; D046911:Macromolecular Substances; D008903:Minerals; D013963:Thyroid Hormones; D014815:Vitamins; D012964:Sodium