The duodenum is the first part of the small intestine, extending from the valve at the bottom of the stomach that regulates stomach emptying (pylorus valve) to the second part of the small intestine (jejunum).
The patient does not absorb as many calories from the foods that are eaten because they never enter the lower part of the stomach nor do they enter the upper part of the small intestine, the duodenum.
These ducts merge into larger and larger channels, like streams flowing into rivers, until they all pour into a single duct that empties into the duodenum (first part of the small intestine).
It involves opening the duodenum channel along its length from the stomach to the next portion of intestine, correcting the duodenal lumen end to end (gastrojejunal anastomosis) so that it is a fully open channel.
There is no gallbladder, and the biliary duct enters the duodenum about 6 in.
The principal duct enters the duodenum with the bileduct, and there is often a second small duct opening separately.
In this sense alone quinine is a tonic. The hydrochloric acid of the gastric juice is stated to convert any salt of quinine into a chloride, and it seems probable that the absorption of quinine takes place mainly from the stomach, for when the drug reaches the alkaline secretions of the duodenum it is precipitated, and probably none of it is thereafter absorbed.
Besides the crypts of Lieberkiihn found throughout the intestinal canal, and the glands of Brunner confined to the duodenum, there are other structures in the mucous membrane, about the nature of which there is still much uncertainty, called " solitary " and " agminated " glands, the latter more commonly known by the name of " Peyer's patches."
The alimentary,or intestinal, canal varies greatly in relative length and capacity in different mammals, and also offers manifold peculiarities of form, being sometimes a simple cylindrical tube of nearly uniform calibre throughout, but more often subject to alterations of form and capacity in different portions of its course - the most characteristic and constant being the division into an upper and narrower and a lower and wider portion, called respectively the small and the large intestine; the former being arbitrarily divided into duodenum, jejunum and ileum, and the latter into colon and rectum.
In the ostrich, Struthio, the craze of overloading the stomach with pebbles which, when triturated into sand, are not voided, has brought about a dislocation, so that the enormously widened and stretched space between proventriculus and gizzard forms a bag, directed downwards, whilst the gizzard itself with part of the duodenum is rotated round its axis to more than loo°.