Biology Notes for Class 11 Science – Pancreas
Here we will discuss Pancreas, one of the important digestive gland. It covers the unit 5, chapter 16 of Class 11 Biology.
PANCREAS
The pancreas is an abdominal organ that is located behind the stomach and is surrounded by other organs, including the spleen, liver and small intestine. The pancreas is about 6 inches (15.24 centimeters) long, oblong and flat. It is located on the back of the abdomen, behind the stomach. The pancreas is connected to the duodenum (the first section of the small intestine) through a small tube called the pancreatic duct. It is an endocrine gland producing several important hormones including insulin, glucagon, somatostatin, and a pancreatic polypeptide which circulate in the blood. The pancreas is also an important digestive organ, secreting pancreatic juice containing bicarbonate to neutralize the acidity of chyme (The partly digested food mixed with gastric juices) which is expelled from the stomach, as well as digestive enzymes that assist digestion and absorption of nutrients in the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme. The pancreas is also known as a mixed gland (it acts as an exocrine as well as endocrine glands)
Pancreatic Juice
The pancreas acts both as an endocrine and exocrine gland. The exocrine part of the gland consists of acini (singular is acinus, the acinus is a small sac-like cavity in a gland, surrounded by secretory cells). The endocrine part includes many cells known as islets of Langerhans. The acinar cells discharge their secretions into the main duct of the gland that communicates with the bile duct and releases their secretion into the duodenum through the sphincter of Oddi.
The exocrine pancreas produces 1200 to 1500 ml of pancreatic juice per day. This juice is colorless and has a pH of about 8. The pancreatic juice contains 1-2% of the organic material and 1% of the inorganic material. The organic matter is mainly protein in the form of enzymes. The most important inorganic component is sodium bicarbonate which makes the pancreatic secretion alkaline. Sodium bicarbonate is secreted from the epithelial cells lining the small pancreatic ducts. The acinar cells secrete several enzymes that help in digestion. One volume of pancreatic juice can neutralize equal volume of acidic gastric content. When the acidic gastric content passes through the pylorus (part of the stomach) into the duodenum, they are partially neutralized by the bicarbonate in the pancreatic juice for the effective enzyme action.
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