The pancreas is a glandular organ in the digestive system and endocrine system of vertebrates. It is both an endocrine gland that produces several important hormones—including insulin, glucagon, somatostatin, and pancreatic polypeptide—and a digestive organ that secretes pancreatic juice that has digestive enzymes that assist the absorption of nutrients and digestion in the small intestine.
These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme. Pancreatic juice is a liquid secreted by the pancreas that contains a variety of enzymes, including trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, pancreatic lipase, nucleases, and amylase.
Pancreatic fluid : A schematic diagram that shows pancreatic acini and the ducts where fluid is created and released. Pancreatic juice is alkaline in nature due to its high concentration of bicarbonate ions that neutralize the gastric acid and allow effective enzymic action. Pancreatic juice secretion is regulated by the hormones secretin and cholecystokinin. It is produced by the walls of the duodenum upon detection of acid food, proteins, fats, and vitamins.
Pancreatic secretion consists of an aqueous bicarbonate component from the duct cells and an enzymatic component from the acinar cells. The main pancreatic enzymes are pancreatic amylase breaks down starch into sugar s , pancreatic lipase breaks down triglyceride s into monoglyceride s and fatty acid s , and pancreatic proteases e. Other components include the nucleases that break down nucleic acids into nucleotides and various peptidases. The secretion of pancreatic juice is regulated by the release of secretin and cholecystokinin from the duodenum when cued by the presence of food components such as protein s, fat s, carbohydrates, etc.
Histologically, the darkly-staining cluster of cells called acini are the cells involved in the secretion of pancreatic enzymes. The lightly-staining cluster of cells are the islets of Langerhans See also:.
Reference s : 1 Khurana, I. Medical Physiology for Undergraduate Students 2nd ed. Elsevier Health Sciences. Nelson Thornes. The evolution of the species of the genus "Homo" led to the emergence of modern humans. Find out more about human evolut.. Once trypsin is formed it activates chymotrypsinogen, as well as additional molecules of trypsinogen. The net result is a rather explosive appearance of active protease once the pancreatic secretions reach the small intestine.
Trypsin and chymotrypsin digest proteins into peptides and peptides into smaller peptides, but they cannot digest proteins and peptides to single amino acids. Some of the other proteases from the pancreas, for instance carboxypeptidase, have that ability, but the final digestion of peptides into amino acids is largely the effect of peptidases on the surface of small intestinal epithelial cells.
More on this later. A major component of dietary fat is triglyceride, or neutral lipid. A triglyceride molecule cannot be directly absorbed across the intestinal mucosa. Rather, it must first be digested into a 2-monoglyceride and two free fatty acids. The enzyme that performs this hydrolysis is pancreatic lipase, which is delivered into the lumen of the gut as a constituent of pancreatic juice. Sufficient quantities of bile salts must also be present in the lumen of the intestine in order for lipase to efficiently digest dietary triglyceride and for the resulting fatty acids and monoglyceride to be absorbed.
This means that normal digestion and absorption of dietary fat is critically dependent on secretions from both the pancreas and liver. Pancreatic lipase has recently been in the limelight as a target for management of obesity.
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