The Pancreas: A Marvel of the Digestive System

The pancreas is unique in that it is involved in both the digestive and endocrine systems. As part of the former, it secretes enzymes into the small intestine, which help break down food into smaller components for proper digestion and absorption. As an endocrine gland, it secretes two hormones crucial to metabolism.

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As part of the endocrine system, the pancreas releases insulin and glucagon, both of which help regulate blood glucose levels. Without them, there would be no way to control the amount of sugar in the bloodstream. Proper secretion of these regulatory substances is essential for normal function; conditions such as diabetes can result from imbalances in insulin and glucagon.

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One of the pancreas' main functions is to aid in digestion. More specifically, the gland releases pancreatic juices into the small intestine through a small duct — one that is normally covered in thin mucus — when there is food in the stomach. Together with bile released from the liver, the enzyme helps the body digest and absorb food.

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If blood glucose levels are too high, the pancreas releases insulin, a hormone that stems from the gland's beta cells. In response, the liver absorbs glucose and stores it as glycogen. Fat and skeletal muscle cells also absorb sugar from the bloodstream. If the pancreas does not produce enough insulin, blood sugar levels will be abnormally high; this is one of the main causes of diabetes.

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In response to low blood sugar levels, the pancreas secretes glucagon, a hormone originating from the organ's alpha cells. Similar to insulin in that it acts on the liver, glucagon's main role is to prevent blood glucose levels from dropping too low. In addition to stimulating the conversion of glycogen to glucose — a process called glycogenolysis — glucagon also promotes the production of glucose from amino acids and reduces the amount of glucose consumed by the liver.

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The pancreas also secretes somatostatin, a hormone that inhibits the secretion of insulin and glucagon. As it moves through the bloodstream, somatostatin also helps regulate the release of other substances such as gastrin and growth hormone; in doing so, the hormone maintains a wide variety of physiological functions. In the nervous system, it acts as a neurotransmitter or chemical messenger.

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Following a meal, the epithelial cells of the pancreas secrete pancreatic juice — an alkaline liquid that contains high concentrations of bicarbonate. These juices are crucial for proper digestion, helping to neutralize stomach acid before it enters the small intestine. A hormone called secretin, which comes from the small intestine, regulates these pancreatic secretions; a deficiency of this regulatory substance may lead to peptic ulcer disease.

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The body cannot absorb dietary fat in its original form. Instead, enzymes must first break down the fats into basic components: fatty acids and glycerol; a pancreatic enzyme called lipase is responsible for this process. Without lipase, the body would be unable to break down fats from digested food, which leads to diarrhea or fatty stools. Significantly low levels of lipase can cause permanent damage to the pancreas.

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Similar to fats, carbohydrates are broken down into simpler compounds prior to absorption. An enzyme called amylase — which is produced and secreted by the pancreas and the salivary glands — carries out this role. People with a shortage of amylase may experience diarrhea due to the effects of undigested starch in the large intestine.

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The pancreas produces two types of proteases or enzymes that break down proteins: trypsin and chymotrypsin. Together with pepsin, a stomach enzyme, they break down protein into amino acids. In addition, proteases help keep the intestine free of pathogens like bacteria. People with protease deficiencies may experience irritability, mood swings, edema, and insomnia; recovery from infections such as those caused by bacteria and viruses may be slower because protease also digests impurities in the blood.

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