part of the gastrointestinal tract following the stomach and followed by the large intestine where much of the digestion and absorption of food takes place primary function is to absorb the nutrients and minerals found in food
average length of the small intestine in an adult male - 22 feet 6 inches (6.9 m) in the adult female - 23 feet 4 inches (7.1 m)
The small intestine is where most digestion takes place.It is structurally divided into three parts: › duodenum › jejunum › ileum
major distinguishing feature is the presence of duodenal (Brunners) glands in the submucosa where most of the breakdown of food in the small intestines occurs. mucous cells of these glands produce an alkaline secretion protects the duodenal lining from the acidity of the chyme raises the luminal pH to the optimum level for pancreatic enzyme activity also the point of entry for the bile and pancreatic ducts exhibits fingerlike or leaflike villi few goblet cells
The duodenum consists of four parts, with the first three forming a "C" shape. › first or superior part begins at the pylors, passing laterally for a short distance before curving into the superior duodenal flexure › second or descending part passes from the superior into the inferior duodenal flexure › third or inferior part passes from the inferior flexure, crossing the major artery and the major vein and also the spinal column › forth or ascending part passes over the aorta, and curves past the pancreas to the duodenojejunal flexure
has long leaflike vilii many plicae circulares an intermediate number of goblet cellsThe key to its identification is that although it has villi (part of the small intestine), it doesn’t contain Brunners glands or Peyers patches.
final and longest section of the small intestine jejunum and ileum both suspended by a double layer of peritoneum that allows these parts to move more freely within the abdomen responsible for the final stages of protein and carbohydrate digestion has fewer villi, which are short and broad- tipped (clublike) relatively abundant goblet cells