b. Pancreatic Enzymes.
(1) Trypsin, chymotrypsin, and carboxypolypeptidase. Trypsin,
chymotrypsin, and carboxypolypeptidase are proteolytic enzymes secreted by the
pancreas. Trypsin and chymotrypsin split whole and partially digested proteins into
amino acids and polypeptides. Carboxypolypeptidase hydrolyzes some polypeptides to
(2) Pancreatic amylase. Pancreatic amylase hydrolyzes starches,
glycogen, and other carbohydrates, with the exception of cellulose, and forms
(3) Pancreatic lipase. Pancreatic lipase hydrolyzes neutral fat into glycerol
and fatty acids.
c. Nervous Regulation. When certain secretions are produced by the
stomach, impulses are simultaneously transmitted by the vagus nerve to the pancreas.
The pancreas in turn produces enzymes and releases them into the pancreatic acini
where they are stored. When food enters the small intestine, the stimulus releases the
218. INTESTINAL SECRETION
a. Hormonal Control. Food in the small intestine causes the secretion of a
hormone known as enterocrinin. This hormone is said to stimulate the secretion of
intestinal enzymes. Enterocrinin, however, is thought to be a very weak hormone and
not of any great importance in the regulation of intestinal secretion.
b. Intestinal Enzymes. Over the whole surface of the small intestine are small
tubular glands known as crypts of Lieberkuhn. At the base of these glands are located
Paneth's cells which secrete the following digestive enzymes:
(1) Peptidase. Several different peptidases are formed in the small
intestine, which serve the purpose of splitting polypeptides into amino acids.
(2) Disaccharidase. The disaccharidases (maltase, lactase, and sucrase)
are formed in the small intestine for splitting their respective disaccharides (maltose,
lactose, and sucrose) into monosaccharides.
(3) Intestinal lipase. Small amounts of lipase are formed in the small
intestine to help split neutral fats into glycerol and fatty acids.
(4) Intestinal amylase. A small amount of amylase is produced in the small
intestine. This amylase is used to break any remaining carbohydrates into