The pancreas is both an exocrine and an endocrine gland of the gastrointestinal system. It produces both digestive enzymes and insulin (via β-islet cells). The pancreas makes insulin and secretes it into the bloodstream to regulate blood sugar and help the body use sugar, without which diabetes would result. The pancreas also makes digestive enzymes used in the small intestine. Even if a pancreas could not make insulin, it still produces the enzymes amylase and lipase, which digest food in the small intestine  .
The pancreas lies across the posterior abdominal wall in the transpyloric plane, extending from the right side of the upper lumbar vertebrae to roughly the hilum of the spleen on the left. It has not retained a mesentery, and so rests on the vertebral bodies, inferior vena cava and aorta. The pancreas has four parts:
- head (an expanded flat part that fits into the concavity of the duodenum)
The lower part of the pancreas projects to the left behind the superior mesenteric vessels as the uncinate process. The narrow neck continues to the left, before expanding again into the elongated body, which passes anterior to the aorta and the left kidney, before tapering into the tail. The main duct of the pancreas usually joins the common bile duct, but there may be a smaller, accessory duct which opens into the duodenum superior to the main duct. The upper, anterior surface of the pancreas is partly related to the lesser sac of the abdominal cavity, which intervenes between it and the stomach, while the lower anterior surface is related to loops of small intestine. The splenic artery courses along the superior border of the pancreas while the splenic vein and terminal parts of the superior and inferior mesenteric veins pass posterior to it.
- The exocrine pancreas is classified as a compound tubuloacinous gland
- The cells that synthesize and secrete digestive enzymes are arranged in grape-like clusters called acini
- These are very similar to what is seen in salivary glands
- In standard histologic sections, most acini are cut obliquely, making it difficult to discern their characteristic shape
- Source: 
|Enzyme||Raw Material||End product|
|Trypsinogen||Reduced proteins||Amino acids|
|Lipase||Fats||Fatty acid and glycerol|
|Amylase||Starch and glycogen||Maltose|