What does it look like?

The pancreas is a fairly large organ, about the size of your hand. It‘s roughly the shape of a bendy parsnip, with a bulgy head stretching out into a long tail. But it’s soft and spongy, not hard. On the outside, it is pale and a bit yellow in colour.

The pancreas is tucked away neatly behind the stomach. It is close to the liver and small intestine, which is important for its function.

A duct (tube) comes out from the bulgy head end of the pancreas. This goes into another duct going from the liver to the small intestine. This biological pipework takes the pancreas’s digestive juices into the gut. The juices enter the small intestine just below the stomach.

You can’t see where hormones are released from the pancreas because the cells release them directly into small blood vessels.

What actually is it?

The pancreas is a gland. Glands produce and release substances that are required by the body. When something is released from a gland, we say it is secreted, and can call it a secretion. There are two ways that the pancreas releases its secretions:

• Digestive enzymes go down a duct into the gut. This type of secretion is called an exocrine secretion.
• Hormones are secreted directly into the blood. This type of secretion is called an endocrine secretion.

Because it does both types of secretion, the pancreas is both an exocrine gland and an endocrine gland. You can find out why glands are named in this way, and more information about what they do, in our article What is a Gland?  

As an endocrine gland, the pancreas is part of the endocrine system. The endocrine system involves many glands which release a huge variety of hormones to control what our cells are doing, and make sure they do it at the right time.

Endocrinologists are experts on the endocrine system. They focus on the pancreas’s endocrine role of making and releasing hormones. 

Digestive enzymes and starch

When you eat food, it must be broken up before it can be absorbed into your body. Mashing it up with your teeth breaks it into small pieces, but these are still too big to be absorbed into your cells. Inside your gut, a combination of chemicals, enzymes and friendly bacteria break the food down into nutrients ready for absorption.

The pancreas helps digestion by secreting litres of liquid into the top of the small intestine every day. This liquid is alkaline, to neutralise the stomach acid. The liquid also contains important digestive enzymes. These are proteins that speed up particular chemical processes. The pancreas releases a mix of enzymes to help break down fats, proteins, and carbohydrates (sugars).

The Pancreas’s carbohydrate-digesting enzyme, Amylase, helps breaks down starch. Starch is the molecule plants use to store the sugar they make from photosynthesis. It’s made by joining sugar molecules together into long chains. White flour is mostly starch – it doesn’t taste sweet, but it can be broken apart to release sugar molecules for absorption. Starch is made from a sugar called glucose which is vital for our bodies, because it is the main energy source for cells.

When you eat a starchy meal, like potatoes, rice or bread, the starch is broken down and glucose is absorbed into the bloodstream.

Glucose in the blood

Glucose is vitally important in the body; every cell needs it as a fuel. For this reason, the body needs to make sure there is always enough glucose in the blood. It also needs to make sure there isn’t too much sugar, as this can be dangerous.

But controlling blood glucose levels is tricky, because the situation is always changing. New glucose floods in after a starchy meal, while cells use up different amounts depending on what they’re doing. Muscle and brain cells are particularly hungry – if you exercise or think hard, then your glucose will be used up faster. The body needs a way to move glucose into and out of the bloodstream to keep blood glucose levels healthy in this ever-changing environment. 

Sugar control hormones 

The pancreas is the main control centre for how sugar moves in the body. It helps cells get the fuel they need, and to avoid blood glucose levels getting too high or low. To achieve this, it uses hormones as chemical messengers. The hormones the pancreas makes include one of the best-known hormones of all: Insulin.

The pancreas cells that make hormones are grouped together in small clumps called Islets of Langerhans. These cells act as hormone factories, with different cells making different hormones. Alpha cells make a hormone called glucagon, and Insulin is made by beta cells. These hormones are stored inside the cells until it’s time to release them.

Alpha and beta cells respond to changes in glucose levels. When glucose levels are high, the beta cells release their insulin into the bloodstream. The blood transports insulin so that it can reach cells in every part of the body.

When cells receive insulin’s message, they change their biological processes. Cells in the liver and muscle take up more glucose from the blood to power their processes, and also store it for later use. Fat cells can also store spare glucose. All this activity reduces blood glucose levels back to normal, which means the pancreas stops releasing insulin. You can find out more about insulin here.

When blood glucose levels are low, the pancreas’ alpha cells release glucagon (find out more here). Glucagon ‘tells’ cells to take glucose out of storage and move back into the blood. This raises blood glucose levels.

By balancing its use of insulin, glucagon, and other hormones, the pancreas keeps blood glucose levels under control. This is a good example of homeostasis . In this way, the pancreas makes sure that cells get enough glucose, and regulates blood glucose to avoid dangerously high blood glucose levels.

The importance of the pancreas is made clear by what happens when things go wrong.

What can go wrong?

Most people will never need to think about their pancreas or what it does. But problems can happen with both its endocrine and exocrine tissues.

Diabetes mellitus

When the insulin signalling system doesn’t work properly, this causes the disease diabetes mellitus. This is by far the most common problem involving the pancreas.

There are different ways the disease can happen. In Type 1 diabetes, the body’s own immune system attacks and destroys the beta cells that make insulin. In Type 2 diabetes, the beta cells don’t produce enough insulin and other cells respond less to insulin’s signal.

Without insulin working properly, blood glucose levels can get dangerously high. But without insulin signalling for them to take in more glucose, liver and muscle cells can’t get enough and start to starve. If left untreated, this all leads to serious problems including damage to blood vessels and dehydration. Find out more about diabetes mellitus here. 

Treatment for diabetes often includes injections of insulin, which take over the job of the pancreas. People using insulin need to monitor their blood glucose levels very carefully. Just like a healthy pancreas, they have to work out when to inject insulin, and how much is required. 

Hormone-producing tumours

Very rarely, hormone-producing cells in the pancreas can mutate and start multiplying in an uncontrolled way to create a tumour. All of these extra cells produce extra hormones; many more than the body needs. This throws the body’s sugar control system out of balance. For example, if too much insulin is released, blood sugar levels can drop dangerously low.

Endocrinologists have to recognise these very rare conditions as well as the more common diseases. Diagnosing and treating unusual diseases is an important part of their job. 

Pancreatitis

The parts of the pancreas that produce and secrete digestive juices can also have problems. In the condition pancreatitis, the digestive enzymes ‘leak’ into the pancreas itself. This damages the pancreas as it starts digesting itself.

In extreme cases it can be necessary for the whole pancreas to be removed. Without a pancreas, the person is unable to make pancreatic hormones like insulin. This means they will need insulin injections like someone with Type 1 diabetes. 

Pancreatic cancer

Pancreatic cancer makes up around 3% of all cancers. It is most common in people over 60 years old. It happens when cells in the pancreas start replicating in an uncontrolled way.

Pancreatic cancer usually starts with cells in the duct that carries digestive juices out of the pancreas. The cancerous cells may also spread to other parts of the body. Pancreatic cancer is difficult to diagnose in its early stages because it doesn’t have obvious symptoms.

Researchers are working to develop better tests for pancreatic cancer. They are also trying to work out who is most at risk, and whether it might help to offer them regular testing.