Many people are unfamiliar with the position and function of the pancreas beyond knowing that "it has something to do with diabetes, doesn't it?" In fact, this organ plays important roles in both digestion and homeostasis, and a good place to begin the tour is John Hopkins University. The introductory pages include instructions on how to locate your own pancreas using the fingers of your right hand – probably best attempted if you can cope with poorly translated assembly instructions and are an advanced practitioner of yoga!

If you want greater detail about the gross structure of the pancreas, and its relation to other organs, there is probably no greater authority than the online Gray's Anatomy. This has a section on the organ's development from dorsal and ventral buds, but the Mammalian Genetics Unit site covers this subject at a cellular level. It points put that exocrine cells, which secrete food-processing enzymes into the duodenum, make up 98% of the pancreas. Endocrine cells, which comprise the remaining 2%, secrete hormones into the bloodstream to maintain blood glucose levels and are clustered together in structures call the Islets of Langerhans. There are four main cell types: a, b, d and PP, which secrete glucagon, insulin, somatostatin and pancreatic polypeptide respectively. Microscope slides of the islets, embedded within the exocrine tissue, can be found here, while there is a good photograph of the acinar structure of the exocrine pancreas here.

The simple outline found here explains that the exocrine pancreas secretes about 20 digestive enzymes and co-factors, and that these account for much of the digestion of dietary proteins, triglycerides and carbohydrates. They also have a role in the cleavage of certain vitamins – including Vitamins A and B12 – from carrier molecules, thereby allowing efficient absorption. With regard to endocrine function, it makes the point that glucagon is a catabolic hormone that mobilises glucose, fatty acids and amino acids from storage into the bloodstream, while insulin has the opposite effect.

Glucagon increases the plasma concentration of glucose via two important metabolic pathways: by stimulating the breakdown of glycogen in the liver and by converting non-sugar substrates, such as amino acids, to glucose (gluconeogenesis). The release of glucagon is triggered by hypoglycaemia, elevated blood levels of amino acids and exercise. Many different aspects of glucagon function and metabolism are covered here.

Insulin is a small protein consisting of an alpha chain of 21 amino acids, linked by two disulphide bridges to a beta chain of 30 amino acids. It has effects on many organs, including the liver, skeletal muscle fibres and fat cells, which result in nutrients from the intestine being stored in the form of insoluble, energy-rich products (glycogen, protein, fat). For a (very!) comprehensive account of the biochemistry involved, take a deep breath and click here.

Diabetes mellitus is a metabolic disorder in which there is an inability to oxidise carbohydrate owing to disturbances in insulin function, giving rise to elevated plasma glucose levels. Sufferers experience extreme thirst and produce copious volumes of glucose-containing urine. If left untreated the disease may lead to fatal ketoacidosis. It is estimated that at least 11 million people have diabetes mellitus in the USA, where it is the leading cause of adult blindness, kidney failure and the amputation of legs or feet.

Insulin-dependent or Type I diabetes mellitus results from destruction of the b cells of the Islets of Langerhans. It is characterised by a reduction in the amount of circulating insulin, most commonly appears in childhood, and is treated by injections of insulin. When the disease has led to kidney failure, patients may now be considered for a combined pancreas and kidney transplant. Data from a UK study carried out in 2002 indicate that the incidence of childhood Type I diabetes will increase by around 10% by the year 2008, despite a decrease in population.

Most cases of diabetes are Type II or non-insulin-dependent. Sufferers tend to be over 30 years old and the incidence increases with age. These patients still produce insulin, although the amount may be inadequate, but the cells of the body, especially fat and muscle cells, lack sensitivity to the hormone. Many people with type 2 diabetes can control their blood glucose by following a careful diet and exercise programme, losing excess weight and taking oral medication. Today there is an alarming increase in the number of people with this condition and the age of onset is becoming younger and younger – some victims are barely in their teens. Most cases are a direct result of poor eating habits, higher body weight, and lack of exercise.

Somatostatin is secreted by the pancreas and also by the intestinal tract and the central nervous system. Its essential function is to inhibit the secretion of other hormones including growth hormone, glucagon and insulin, and many gastrointestinal hormones. Clinically, it is effective in combating giantism and acromegaly, and is also used to treat a variety of neoplasms.

Inflammation of the pancreas – pancreatitis – can lead to life-threatening conditions such as acute respiratory distress syndrome, renal failure, cardiac depression, haemorrhage and hypotensive shock. The most common causes are alcohol abuse and biliary stone disease. Interestingly, age and ethnic origin have a striking effect upon the incidence; in the US, the risk for African Americans aged between 35 and 64 is 10 times higher than for any other group.

Pancreatic cancer is a leading cause of cancer death, and 29,000 new cases are diagnosed in the United States each year. According to the patient-orientated information at, risk factors include smoking, increasing age, diabetes, a family history and chronic pancreatitis. This site also has a clear explanation of the symptoms, diagnosis and all aspects of treatment. For a professional perspective, try the University of Bonn site. It points out that the incidence of carcinoma of the pancreas has increased markedly over the past few decades, and despite the high mortality rate its aetiology is poorly understood. Nevertheless, there are some promising lines of research which could lead to improved treatment in the future, in fields as diverse as gene therapy, monoclonal antibodies and therapeutic vaccination.

This tour was submitted by Derrick Garwood, a Freelance Medical Writer and Editor. If you have any comments on this article, please feel free to email Derrick.

The tours presented here were accurate at the time of publication, but remember that information on the Web has a tendency to change without notice!

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