|
The human gastrointestinal tract, or GI tract, or GIT is an organ system responsible for consuming and digesting foodstuffs, absorbing nutrients, and expelling waste. The tract consists of the stomach and intestines, and is divided into the upper and lower gastrointestinal tracts. By the broadest definition, the GI tract includes all structures between the mouth and the anus.However, the digestive system is a broader term that includes other structures, including the digestive organs and their accessories. The tract may also be divided into foregut, midgut, and hindgut, reflecting the embryological origin of each segment. The whole digestive tract is about nine metres (30 feet) long. The GI tract releases hormones from enzymes to help regulate the digestive process. These hormones, including gastrin, secretin, cholecystokinin, and ghrelin, are mediated through either intracrine or autocrine mechanisms, indicating that the cells releasing these hormones are conserved structures throughout evolution.〔Nelson RJ. 2005. Introduction to Behavioral Endocrinology. Sinauer Associates: Massachusetts. p 57.〕 ==Structure== The structure and function can be described both as gross anatomy and as microscopic anatomy or histology. The tract itself is divided into upper and lower tracts, and the intestines small and large parts.〔(【引用サイトリンク】title=Length of a Human Intestine )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Human gastrointestinal tract」の詳細全文を読む スポンサード リンク
|