The digestive system consists of two parts, the gastrointestinal (GI) tract and the major digestive accessory glands, which include the
liver and pancreas. This review will only focus on the control systems that regulate the various functions of the gastrointestinal tract.
The gastrointestinal tract is a tube-like structure which extends from the mouth to the anus. Histologically, the gut consists
of four main layers: the mucosa, which comprises epithelial cells (enterocytes, endocrine cells and others), the lamina propria and the
muscularis mucosae; the submucosa; two muscle layers, an inner thick circular layer and an outer thin longitudinal layer; and
a serosal layer. Functionally, the gastrointestinal tract supplies the body, including the gut itself, with nutrients, electrolytes and water
by performing five distinct functions: motility, secretion, digestion,absorption and storage. The gut orchestrates these functions by two
control systems, intrinsic and extrinsic. The intrinsic control system is located between the different layers of the gut, whereas the extrinsic
control system resides outside the wall of the gut. Each of these systems consists of two components, namely, nerves and endocrine secretions.
The intrinsic control system has two components: the Enteric Nervous System (ENS) and gut hormones, which include gastrin, Gastric
Inhibitory Peptide (GIP), Cholecystokinin (CCK), secretin, and motilin.The extrinsic control system elements that regulate gut functions consist
of the vagus and splanchnic nerves and the hormone aldosterone.
Last date updated on July, 2014