What is the pancreas? What is its function?

Basic understanding and historical origins of the pancreas

pancreasThis organ, hidden deep within the human abdominal cavity, has been the subject of medical exploration since ancient times. Its discovery can be traced back to the 3rd century BC, when the ancient Greek anatomist Herophilus first described this glandular structure, but at that time, he knew nothing about its function. Centuries later, another ancient Greek physician, Galen, named it "pancreas," derived from the Greek words "pan" (all) and "kreas" (flesh), meaning "whole flesh," reflecting the intuitive understanding of its structure at that time.

Today, we know that the pancreas is a long, slender gland located deep in the upper abdomen, stretching across the retroperitoneal cavity. It is about 12-15 centimeters long and weighs only 70-100 grams, roughly the weight of a smartphone. Its anatomical location is extremely concealed: it is shielded from view by the stomach in front, closely attached to the spine behind, surrounded by the duodenum on the right, and extends to the vicinity of the spleen on the left (Figure 1). This well-hidden location serves as both a protective mechanism and a challenge for clinical diagnosis.

Schematic diagram of the anatomical location of the pancreas

The diagram shows a cross-section of the human abdomen, marking the relative positions of the pancreas and surrounding organs: stomach (front), duodenum (right side), common bile duct (passing through the head of the pancreas), spleen (left side), and spine (posterior side).

The pancreas's dual role: exocrine and endocrine system

The pancreas is unique in that it possesses both exocrine and endocrine functions, a dual identity that was not fully elucidated until the late 19th century. In 1889, German physicians Joseph von Mering and Oskar Minkowski, after removing the pancreas from dogs in an experiment, observed diabetic symptoms in the animals, thus establishing for the first time the link between the pancreas and glucose metabolism. In 1921, Canadian scientists Frederick Banting and Charles Best successfully isolated insulin, revolutionizing the history of diabetes treatment.

Structurally, the pancreas consists of two main functional tissues: exocrine acini and endocrine islets. The exocrine portion, comprising 95% of the pancreatic tissue, is responsible for producing digestive enzymes; while the endocrine islets, comprising only 1-2% of the pancreatic tissue, play a crucial role in regulating metabolism. This ingenious division of functions makes the pancreas the core hub of the human digestive and metabolic system.

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The intricate functions and operating mechanisms of the pancreas

Exocrine function: the chemical factory of the digestive system

The pancreas's exocrine function is arguably one of the most efficient chemical factories in the human body. Daily, a healthy pancreas secretes approximately 1.5-2 liters of pancreatic juice, containing a large amount of digestive enzymes and bicarbonate. These digestive enzymes are divided into three main categories:

1. amylaseResponsible for breaking down carbohydrates
2. protease(e.g., trypsinogen, chymotrypsinogen): responsible for breaking down proteins.
3. LipaseResponsible for breaking down fat

These enzymes are initially stored in an inactive form (zymogens) and are only activated after entering the duodenum, thus preventing the digestion of the pancreas itself. If this self-protective mechanism malfunctions, it can lead to acute pancreatitis.

The regulation of pancreatic juice secretion is a sophisticated process controlled by both nerves and hormones. After food enters the duodenum, intestinal mucosal cells secrete secretin and cholecystokinin, which stimulate the pancreas to increase secretion through blood circulation. This reaction is extremely rapid, usually starting within 1-2 minutes after food enters the small intestine (Table 1).

Pancreatic exocrine response timeline

stage	Time	Secretion characteristics	Stimuli
First installment	0-2 minutes	Enzyme-rich secretion	Sense of smell, taste, and chewing
stomach period	2-5 minutes	moderate secretion	Gastric dilatation, food chemicals
Intestinal phase	5+ minutes	Large amounts of fluid and enzyme secretion	Acidity and fat content of chyme in the duodenum

Endocrine function: the command center for blood glucose regulation

The endocrine function of the pancreas is mainly carried out by 1-1.5 million Langerhans islets scattered throughout the gland. Each islet is a miniature biochemical regulatory center, containing various hormone-secreting cells:

• α cells: Secretes glucagon, increasing blood glucose concentration
• β cells: Secretes insulin to lower blood glucose levels
• δ cellsSecreting hormones regulates α and β cell function.
• PP cellsSecretion of pancreatic polypeptides regulates exocrine function.

These cells together form a sophisticated blood glucose feedback system. When blood glucose rises (such as after a meal), β cells rapidly release insulin within 10 minutes to promote glucose uptake by the cells; when blood glucose falls, α cells release glucagon within 5-15 minutes to prompt the liver to release stored glucose (Figure 2).

Postprandial blood glucose regulation time series

Time (minutes)	Blood glucose level (mg/dL)	Insulin concentration (μU/mL)	Physiological stages and explanations
0	95	12	Fasting baseline statusBlood sugar and insulin levels are both at baseline.
30	165	75	Rapid reaction periodBlood sugar rises rapidly;Insulin secretion reaches its peakTo cope with soaring blood sugar.
60	185	65	Peak blood glucose period:Blood glucose concentration reaches its peakInsulin maintains a high level of secretion.
90	155	45	pullback periodThe insulin effect becomes apparent, and blood sugar begins to decline steadily; insulin secretion then decreases accordingly.
120	125	25	Key diagnostic pointsClinically, the 120-minute value is often used as an important basis for the diagnosis of diabetes.
150	105	18	Recovery periodBlood sugar is close to the normal range, and insulin secretion is close to the basal level.
180	97	14	Restore basic stateBlood sugar and insulin levels have basically returned to fasting levels.

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Data Interpretation and Key Conclusions

1. Rapid response of insulinAs can be seen from the table, insulin concentration rises sharply to a peak (75 μU/mL) within 30 minutes of the onset of blood glucose rise, which shows that healthy pancreatic β-cells are highly sensitive and efficient.
2. Blood sugar peaks and declinesBlood glucose levels peaked at around 185 mg/dL at approximately 60 minutes, then continued to decline under the influence of insulin, dropping significantly to 125 mg/dL at 120 minutes, and almost returning to fasting levels at 180 minutes. This reflects the body's effective glucose regulation capacity.
3. dynamic equilibriumThe changing trends of the two sets of data clearly demonstrate... "Elevated blood sugar → Stimulation of insulin secretion → Blood sugar is utilized and stored → Blood sugar decreases → Reduced insulin secretion" This perfect negative feedback regulatory mechanism is one of the core functions of the pancreas.

Maintaining this dynamic balance is crucial for the human body. Studies have shown that various cells within the pancreas regulate each other through paracrine mechanisms, forming a highly autonomous microregulatory system capable of responding to changes in blood glucose levels within seconds.

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Pancreas-related diseases and health threats

disease	Incidence	mortality rate	15-Year Trend (2010→2025)	Major risk factors
Acute pancreatitis	34	1.2	↑ 22 %	Gallstones, alcoholism
Chronic pancreatitis	9	0.8	↑ 15 %	Long-term alcoholism and smoking
pancreatic cancer	7.2	6.6	↑ 30 %	Smoking, obesity, diabetes
Newly diagnosed insulin-dependent diabetes mellitus	15	0.2	↑ 18 %	Autoimmunity, environmental triggers
Type 2 diabetes (newly diagnosed)	520	12	↑ 40 %	Obesity, sedentary lifestyle, high-calorie diet

Inflammatory diseases of the pancreas: Acute and chronic pancreatitis

Pancreatitis is one of the most common diseases of the pancreas, and can be divided into acute and chronic types. Acute pancreatitis is usually a sudden onset of inflammation, with a global annual incidence of approximately 13-45 cases per 100,000 people. Its main causes include gallstones (40%) and alcohol abuse (35%), while other causes include hypertriglyceridemia, certain medications, and genetic factors.

The clinical course of acute pancreatitis can be divided into three time phases:

1. Initial stage (0-7 days)Local inflammatory reactions may lead to organ failure.
2. Mid-term (1-2 weeks)Necrotic tissue formation may lead to secondary infection.
3. Later stage (2 weeks or more)Complications appear or gradually recover

Chronic pancreatitis is a long-term, irreversible inflammatory process characterized by pancreatic parenchymal fibrosis and loss of function. Chronic alcohol abuse is a major risk factor, accounting for 70-80% of cases. Patients with chronic pancreatitis have a significantly increased risk of pancreatic cancer, 15-20 times higher than the general population.

Comparison of acute and chronic pancreatitis

feature	Acute pancreatitis	Chronic pancreatitis
Pathological changes	Reversible inflammation	Irreversible fibrosis
Main symptoms	Severe upper abdominal pain	Recurrent abdominal pain, steatorrhea
Endocrine function	Usually reserved	Later loss (diabetes)
Exocrine function	Temporarily affected	Progressive loss
Peak age of onset	50-60 years old	40-50 years old

Metabolic diseases: The link between diabetes and the pancreas

Diabetes, the most well-known pancreas-related disease, has become a global health crisis. According to data from the International Diabetes Federation (IDF) in 2021, approximately 537 million adults worldwide have diabetes, a number projected to rise to 783 million by 2045. Diabetes is mainly divided into two categories:

1. Type 1 diabetes: Caused by the destruction of pancreatic β cells by autoimmune disease, usually occurs in childhood and adolescence, accounting for 5-10% of diabetes cases.
2. Type 2 diabetesCaused by insulin resistance and gradual decline in β-cell function, accounting for 90-95% of TP3T cases.

diabetesThe development of diabetes can take years or even decades. In the prediabetes stage, pancreatic beta cells proliferate compensatorily and over-secrete insulin to overcome insulin resistance. Over time, beta cells gradually deplete, insulin secretion becomes insufficient, eventually leading to elevated fasting blood glucose and a diagnosis of diabetes (Figure 3).

Figure 3: The multi-stage physiological evolution from health to diabetes

stage	Time span	Blood sugar status	Insulin sensitivity	pancreatic β-cell function	Insulin levels	Key features and descriptions
1. Normal glucose tolerance	–	normal	normal	normal	normal	The body can effectively process glucose, and blood sugar levels are consistently maintained within the normal range. This is an ideal state of health.
2. Insulin resistance	Initial period (May last for many years)	normal (on an empty stomach and after a meal)	Started to fall	Compensatory enhancement	Slightly elevated	Muscle, fat, and liver cells become less responsive to insulin. To maintain normal blood sugar levels, the pancreas must work harder. This stage is usually asymptomatic but may be accompanied by metabolic problems such as obesity and high blood pressure.
3. Compensatory hyperinsulinemia	Compensation period (Sustainable for 5-10 years or longer)	normal (fasting) Minor abnormality (After the meal)	Significant decline	Overcompensation	Significantly increased	Pancreatic beta cells overcome insulin resistance by secreting excessive amounts of insulin, barely maintaining fasting blood glucose within the normal range, but postprandial blood glucose may begin to fluctuate slightly and rise.
4. Decline in β-cell function	Pre-compensation	abnormal fasting blood glucose (IFG) Glucose intolerance (IGT)	Severe decline	The decline began	Gradually declining from the peak	Due to prolonged overwork, pancreatic beta cells begin to fatigue, experience functional decline, and may even undergo apoptosis. Their ability to secrete insulin decreases, making it unable to suppress hepatic glucose output, leading to elevated fasting blood glucose. This stage is known as "prediabetes."
5. Impaired glucose tolerance (Prediabetes)	Decompensation period	IFG + IGT	Severe resistance	Continued recession	decline	Blood sugar levels are significantly higher than normal, but have not yet met the diagnostic criteria for diabetes. This is the last critical window of opportunity for diabetes prevention.
6. Obvious diabetes	Diagnosis and progression	Diagnostic criteria for diabetes (fasting ≥126 mg/dL) ≥200 mg/dL after a meal	Severe resistance	Significant failure	low	The function of pancreatic β cells is severely impaired, resulting in a severe deficiency of insulin secretion and an inability to control blood sugar. Both fasting and postprandial blood sugar levels remain consistently high, exhibiting typical diabetic symptoms such as polyuria, polydipsia, polyphagia, and weight loss. Blood sugar control requires lifestyle interventions and medication.

This table clearly demonstrates why type 2 diabetes is a progressive disease and highlights the extreme importance of early screening and intervention before symptoms appear.

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Key points

1. Long incubation periodThe development of type 2 diabetes is a gradual process that can take years or even decades, which provides...Early intervention and preventionIt provided a valuable window of time.
2. Insulin resistance is the starting pointThis is usually the triggering factor for the whole process, and it is closely related to obesity, lack of exercise, genetics, etc.
3. β-cell exhaustion is a key turning pointThe progression from "compensatory hyperinsulinemia" to "β-cell dysfunction" represents a shift from normal to abnormal blood glucose levels.Key turning pointOnce beta cell function declines to a certain extent, diabetes is almost inevitable.
4. Prediabetes is reversible.In the "impaired glucose tolerance" stage, there is a high chance that intensive lifestyle changes (weight loss, exercise, dietary adjustments) can slow or reverse disease progression and prevent the development of full-blown diabetes.

Pancreatic tumors: the silent killer

The most worrying type of pancreatic cancer is pancreatic ductal adenocarcinoma, known as the "silent killer" due to its extremely high mortality rate. According to global cancer statistics (GLOBOCAN 2020), there are approximately 496,000 new cases of pancreatic cancer and 466,000 deaths annually, with the mortality rate almost equal to the incidence rate, reflecting its extremely poor prognosis.

Risk factors for pancreatic cancer include:

• Smoking (increases risk by 2-3 times)
• Chronic pancreatitis (risk increased 15-20 times)
• Diabetes (risk increased by 1.5-2 times)
• Family history (5-10% cases have genetic factors)
• Obesity and advanced age

Pancreatic cancer typically develops over a latency period of many years. From the initial gene mutation to the formation of a detectable tumor, it takes an average of 10-15 years. However, once a clinically identifiable tumor forms, the disease often progresses rapidly and aggressively. Due to the lack of obvious early symptoms, patients with more than 80% are already at an advanced stage at the time of diagnosis, losing the opportunity for radical surgical treatment.

Pancreatic cancer staging and 5-year survival rate

Installments	Tumor extent	Surgical feasibility	5-year relative survival rate
Phase I	Limited to the pancreas	Resectable	25-30%
Phase II	Local diffusion	Possibly resectable	10-12%
Phase III	Invasion of major blood vessels	Margin can be excised	6-8%
Phase IV	Distant transfer	Unresectable	1-3%

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Pancreatic health maintenance and disease prevention

Lifestyle and Pancreatic Health

Maintaining pancreatic health requires a comprehensive approach, involving diet, exercise, and lifestyle habits. The following key strategies are based on extensive epidemiological studies:

1. Quit smoking and limit alcohol consumptionSmoking is the most definitive risk factor for pancreatic cancer; the risk can be reduced by 30% after quitting smoking for 10 years. Alcohol intake should be limited to the standard daily limit (≤2 drinks for men, ≤1 drink for women).
2. Balanced dietAdopt a Mediterranean diet, rich in fruits, vegetables, whole grains, and healthy fats. Pay special attention to limiting the intake of red and processed meats, which are associated with an increased risk of pancreatic cancer.
3. Weight ManagementObesity (BMI ≥ 30) increases the risk of pancreatic cancer. Maintaining a healthy weight (BMI 18.5-24.9) is crucial for pancreatic protection.
4. Blood sugar controlEven for non-diabetic individuals, maintaining stable blood sugar levels can reduce the burden on the pancreas. Avoid high-sugar diets and foods that cause rapid blood sugar spikes.

Oriented	suggestion
diet	The Mediterranean diet (high in fiber, olive oil, and deep-sea fish), limited alcohol (men <20 g/day, women <10 g/day), and avoidance of fried and processed meats.
sports	≥150 minutes of moderate-intensity aerobic exercise per week plus 2 resistance training sessions can reduce insulin resistance by 25 %.
Weight Management	BMI maintained between 18.5 and 24; waist circumference <90 cm for men and <80 cm for women.
Quit smoking	Smokers have a 70% increased risk of pancreatic cancer (TP3T), but the risk drops to the level of non-smokers after 10 years of quitting smoking.
Screening	Those with a family history or genetic mutations: annual EUS + MRI; patients with chronic pancreatitis: imaging + CA-19-9 every 6 months.
Be alert to early symptoms	If you experience persistent upper abdominal pain, jaundice, new-onset diabetes, or oily stools, you should seek medical attention immediately.

Early screening and monitoring of high-risk groups

Early screening can save lives for people at high risk of pancreatic cancer. High-risk groups include:

• A first-degree relative has a family history of pancreatic cancer.
• Known to carry related gene mutations (such as BRCA1/2, CDKN2A).
• Suffering from hereditary pancreatitis
• Newly diagnosed diabetes in individuals over 50 years of age accompanied by weight loss

Current recommended screening strategies include regular imaging examinations (endoscopic ultrasound or MRI/MRCP) and blood biomarker testing (CA19-9, etc.). Screening typically begins at age 50, or 10 years earlier than the age of the youngest patient in the family.

Medical Advances and Future Prospects

The field of pancreatic medicine is rapidly evolving. In diagnostics, liquid biopsy technology, by detecting circulating tumor DNA and exosomes in the blood, promises to enable early, non-invasive diagnosis. In treatment, immunotherapy, targeted therapy, and personalized medicine strategies offer new hope for patients with advanced-stage disease.

Artificial intelligence-assisted diagnostic systems are also beginning to be applied in the field of pancreatic diseases, improving the recognition rate of early lesions by analyzing medical images. Studies have shown that the sensitivity of AI systems in detecting early pancreatic cancer can reach over 90%, higher than that of experienced radiologists.

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Cherish the silent organs

Although the pancreas is an unsung organ in the body, it bears the dual responsibility of digestion and metabolism. Its intricate structure and function reflect the marvelous design of human physiology, while its vulnerability to disease reminds us to pay attention to this long-underestimated organ.

By understanding the pancreas's functions, diseases, and protective measures, we can better maintain the health of this vital organ. With future medical advancements, we believe we will be able to more effectively address pancreatic diseases, unlock more mysteries of this "silent organ," and bring new benefits to human health.

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