The pancreas, an organ located behind the stomach in the upper abdomen, plays a dual role in the body. It functions as both a digestive gland and a hormone-producing organ. This unique gland supports the body in breaking down food and managing sugar levels.
Cells for Digestion: The Exocrine Pancreas
The majority of the pancreas, about 95%, is made up of exocrine tissue responsible for digestion. This exocrine tissue contains specialized acinar and duct cells, which produce pancreatic juice. Pancreatic juice breaks down food in the small intestine.
Acinar cells produce and secrete a variety of digestive enzymes, including amylase for carbohydrates, lipase for fats, and proteases like trypsin and chymotrypsin for proteins. These enzymes are initially in an inactive form to prevent them from digesting the pancreas itself. They become active once they reach the small intestine, specifically the duodenum, where they facilitate the breakdown of nutrients for absorption.
Duct cells line the pancreatic ducts and have an important role. They secrete bicarbonate, which neutralizes acidic chyme entering the small intestine from the stomach. This bicarbonate creates an optimal alkaline environment for pancreatic digestive enzymes to function effectively. Duct cells also transport enzymes from acinar cells into the duodenum.
Cells for Hormones: The Endocrine Pancreas
Beyond digestion, the pancreas also functions as an endocrine gland, producing hormones that regulate various bodily processes. This function is carried out by specialized cell clusters known as the Islets of Langerhans. These islets are scattered throughout the pancreatic tissue, making up a small but significant portion of the organ’s mass.
The Islets of Langerhans primarily maintain stable blood sugar levels. They release hormones directly into the bloodstream, which travel to target cells throughout the body. The islets contain several types of hormone-producing cells, ensuring glucose homeostasis by balancing sugar for energy and storage.
Key Endocrine Cell Types
The Islets of Langerhans house several distinct cell types, each producing a specific hormone for blood sugar regulation and other metabolic functions. These cells communicate to finely tune hormone release. Understanding these individual cell types reveals the intricate control mechanisms within the pancreas.
Alpha cells, about 20% of islet cells, produce glucagon. Glucagon raises blood glucose levels when they fall too low, such as between meals or during fasting. It signals the liver to convert stored glycogen into glucose and release it into the bloodstream (glycogenolysis). Glucagon also promotes the liver and kidneys to create new glucose from other sources, like amino acids.
Beta cells are the most abundant islet cell type (50-70%), producing insulin. Insulin’s primary function is to lower blood glucose levels after a meal by promoting glucose absorption into cells for energy or storage. It helps liver, fat, and muscle cells take up glucose, converting it into glycogen or fats. Problems with beta cells can lead to conditions like diabetes.
Delta cells secrete somatostatin, which influences the release of other pancreatic hormones. Somatostatin inhibits both insulin and glucagon secretion, creating a regulatory feedback loop that maintains balanced blood sugar levels. These cells are distributed throughout the islets and respond to factors such as glucose levels.
PP cells (pancreatic polypeptide cells) produce pancreatic polypeptide. This hormone influences various digestive processes. Pancreatic polypeptide inhibits pancreatic exocrine secretion and gallbladder contraction, affecting how food is processed and absorbed. Its release is stimulated by eating (especially high-protein meals), fasting, and exercise.