Pancreas – Anatomy, Types, Structure, Functions

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The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas has both an endocrine and a digestive exocrine function. As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide. As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct. This juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and digestive enzymes, which break down carbohydrates, proteins, and fats in food entering the duodenum from the stomach.

The pancreas is an extended, accessory digestive gland that is found retroperitoneally, crossing the bodies of the L1 and L2 vertebra on the posterior abdominal wall. The pancreas lies transversely in the upper abdomen between the duodenum on the right and the spleen on the left. It is divided into the head, neck, body, and tail. The head lies on the inferior vena cava and the renal vein and is surrounded by the C loop of the duodenum. The tail of the pancreas extends up to the splenic hilum. The pancreas produces an exocrine secretion (pancreatic juice from the acinar cells) which then enters the duodenum through the main and accessory pancreatic ducts and endocrine secretions (glucagon and insulin from the pancreatic islets of Langerhans) that enter the blood.

Structure

The Parts of the Pancreas

Your doctor may refer to the parts of the pancreas when discussing your disease. The tumor’s location in the pancreas is important since it affects the symptoms and treatment of your disease.
FOUR MAIN PARTS
  • Head – The head is the widest part of the pancreas. The head of the pancreas is found in the right side of abdomen, nestled in the curve of the duodenum (first part of the small intestine).
  • Neck – The neck is the thin section of the gland between the head and the body of the pancreas.
  • Body – The body is the middle part of the pancreas between the neck and the tail. The superior mesenteric artery and vein run behind this part of the pancreas.
  • Tail – The tail is the thin tip of the pancreas in the left side of the abdomen, in close proximity to the spleen.

[Uncinate process – The uncinate is the part of the head that hooks towards the back of the abdomen around two very important blood vessels—the superior mesenteric artery and the superior mesenteric vein.

The pancreas (shown here in pink) sits behind the stomach, with the body near the curvature of the duodenum, and the tail stretching to touch the spleen.

The pancreas is an organ that in humans lies in the abdomen, stretching from behind the stomach to the left upper abdomen near the spleen. In adults, it is about 12–15 centimeters (4.7–5.9 in) long, lobulated, and salmon-colored in appearance.

Anatomically, the pancreas is divided into the headneckbody, and tail. The pancreas stretches from the inner curvature of the duodenum, where the head surrounds two blood vessels: the superior mesenteric artery, and vein. The longest part of the pancreas, the body, stretches across behind the stomach, and the tail of the pancreas ends adjacent to the spleen.[rx]

Two ducts, the main pancreatic duct, and a smaller accessory pancreatic duct, run through the body of the pancreas, joining with the common bile duct near a small ballooning called the ampulla of Vater. Surrounded by a muscle, the sphincter of Oddi, this opens into the descending part of the duodenum.[rx]

Parts

The head of the pancreas sits within the curvature of the duodenum and wraps around the superior mesenteric artery and vein. To the right sits the descending part of the duodenum and between these travel the superior and inferior pancreaticoduodenal arteries. Behind rests the inferior vena cava, and the common bile duct. In front sits the peritoneal membrane and the transverse colon.[rx] A small uncinate process emerges from below the head, situated behind the superior mesenteric vein and sometimes the artery.[rx]

The neck of the pancreas separates the head of the pancreas, located in the curvature of the duodenum, from the body. The neck is about 2 cm (0.79 in) wide and sits in front of where the portal vein is formed. The neck lies mostly behind the pylorus of the stomach and is covered with the peritoneum. The anterior superior pancreaticoduodenal artery travels in front of the neck of the pancreas.[rx]

The body is the largest part of the pancreas and mostly lies behind the stomach, tapering along its length. The peritoneum sits on top of the body of the pancreas, and the transverse colon in front of the peritoneum.[rx] Behind the pancreas are several blood vessels, including the aorta, the splenic vein, and the left renal vein, as well as the beginning of the superior mesenteric artery.[rx] Below the body of the pancreas sits some of the small intestines, specifically the last part of the duodenum and the jejunum to which it connects, as well as the suspensory ligament of the duodenum which falls between these two. In front of the pancreas sits the transverse colon.[rx]

The pancreas narrows towards the tail, which sits near to the spleen.[rx] It is usually between 1.3–3.5 cm (0.51–1.38 in) long, and sits between the layers of the ligament between the spleen and the left kidney. The splenic artery and vein, which also passes behind the body of the pancreas, pass behind the tail of the pancreas.[rx]

Blood supply

The pancreas has a rich blood supply, with vessels originating as branches of both the coeliac artery and the superior mesenteric artery.[rx] The splenic artery runs along the top of the pancreas and supplies the left part of the body and the tail of the pancreas through its pancreatic branches, the largest of which is called the greater pancreatic artery.[rx] The superior and inferior pancreaticoduodenal arteries run along the back and front surfaces of the head of the pancreas adjacent to the duodenum. These supply the head of the pancreas. These vessels join together (anastomose) in the middle.[rx]

The body and neck of the pancreas drain into the splenic vein, which sits behind the pancreas.[rx] The head drains into, and wraps around, the superior mesenteric and portal veins, via the pancreaticoduodenal veins.[rx]

The pancreas drains into lymphatic vessels that travel alongside its arteries and has a rich lymphatic supply.[rx] The lymphatic vessels of the body and tail drain into splenic lymph nodes, and eventually into lymph nodes that lie in front of the aorta, between the coeliac and superior mesenteric arteries. The lymphatic vessels of the head and neck drain into intermediate lymphatic vessels around the pancreaticoduodenal, mesenteric and hepatic arteries, and from there into the lymph nodes that lie in front of the aorta.[rx]

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Arterial Supply

Branches of the splenic artery (a branch of the celiac trunk), superior mesenteric artery (SMA), and the common hepatic artery provide blood supply to the pancreas .

  • Pancreatic head: The gastroduodenal artery (a branch of the common hepatic artery) supplies the head and the uncinate process of the pancreas in the form of the pancreaticoduodenal artery (PDA). Part of the inferior portion of the head is supplied by the inferior PDA which arises from the SMA.
  • Body and the tail: The splenic artery and its branches supply these.

Venous Supply

  • Pancreatic head: The head drains into the superior mesenteric vein (SMV).
  • Body and the neck: The splenic vein drains these.

The SMV and splenic vein merge to form the portal vein.

Nerves

The pancreas has a complex network of parasympathetic, sympathetic, and sensory innervations . It also has an intrinsic nerve plexus. Sympathetic and parasympathetic fibers are dispersed to pancreatic acinar cells. The parasympathetic fibers arise from the posterior vagal trunk and are secretomotor, but the secretions from the pancreas are predominantly mediated by cholecystokinin and secretin, which are hormones produced by the epithelial cells of the duodenum and proximal intestinal mucosa regulated by acidic compounds from the stomach. Sympathetic innervation is via the T6-T10 thoracic splanchnic nerves and the celiac plexus.

Overview of Pancreatic Islets

Pancreatic islets, also called the islets of Langerhans, are regions of the pancreas that contain its hormone-producing endocrine cells.

Key Points

The pancreatic islets are small islands of cells that produce hormones that regulate blood glucose levels. Hormones produced in the pancreatic islets are secreted directly into the bloodstream by five different types of cells.

The alpha cells produce glucagon and makeup 15–20% of total islet cells. The beta cells produce insulin and amylin and makeup 65–80% of the total islet cells. The delta cells produce somatostatin and makeup 3–10% of the total islet cells.

The gamma cells produce pancreatic polypeptide and makeup 3–5% of the total islet cells. The epsilon cells produce ghrelin and make up less than 1% of the total islet cells.

The feedback system of the pancreatic islets is paracrine and is based on the activation and inhibition of the islet cells by the endocrine hormones produced in the islets.

Key Terms

endocrine: Produces internal secretions that are transported around the body by the bloodstream.

paracrine: Describes a hormone or other secretion released from endocrine cells into the surrounding tissue rather than into the bloodstream.

exocrine: Produces external secretions that are released through a duct.

The pancreas serves two functions, endocrine and exocrine. The exocrine function of the pancreas is involved in digestion, and these associated structures are known as the pancreatic acini.

The pancreatic acini are clusters of cells that produce digestive enzymes and secretions and make up the bulk of the pancreas. The endocrine function of the pancreas helps maintain blood glucose levels, and the structures involved are known as the pancreatic islets, or the islets of Langerhans.

This is an illustration of the pancreas with a detailed view of a pancreatic islet with endocrine cells. The islet is surround by the pancreatic acini and pancreatic duct.

Pancreatic islets or islets of Langerhans: The islets of Langerhans are the regions of the pancreas that contain its endocrine (hormone-producing) cells.

The pancreatic islets are small islands of cells that produce hormones that regulate blood glucose levels. Hormones produced in the pancreatic islets are secreted directly into the blood flow by five different types of cells.

This is a photo taken through a microscope of pancreatic tissue. The small cells in the middle are beta cells, and the surrounding larger cells are alpha, delta, gamma, and epsilon cells.

Pancreatic tissue: The small cells in the middle are beta cells, and the surrounding larger cells are alpha, delta, gamma, and epsilon cells.

The endocrine cell subsets are:
  • Alpha cells produce glucagon and make up 15–20% of total islet cells. Glucagon is a hormone that raises blood glucose levels by stimulating the liver to convert its glycogen into glucose.
  • Beta cells produce insulin and amylin and makeup 65–80% of the total islet cells. Insulin lowers blood glucose levels by stimulating cells to take up glucose out of the bloodstream. Amylin slows gastric emptying, preventing spikes in blood glucose levels.
  • Delta cells produce somatostatin and makeup 3–10% of the total islet cells. Somatostatin is a hormone that suppresses the release of the other hormones made in the pancreas.
  • Gamma cells produce pancreatic polypeptide and makeup 3–5% of the total islet cells. Pancreatic polypeptide regulates both the endocrine and exocrine pancreatic secretions.
  • Epsilon cells produce ghrelin and make up less than 1% of the total islet cells. Ghrelin is a protein that stimulates hunger.

The feedback system of the pancreatic islets is paracrine—it is based on the activation and inhibition of the islet cells by the endocrine hormones produced in the islets. Insulin activates beta cells and inhibits alpha cells, while glucagon activates alpha cells, which activates beta cells and delta cells. Somatostatin inhibits the activity of alpha cells and beta cells.

Types of Cells in the Pancreas

The islets of Langerhans are the regions of the pancreas that contain many hormone-producing endocrine cells.

Key Points

The pancreas reveals two different types of parenchymal tissue: exocrine acini ducts and the endocrine islets of Langerhans.

The hormones produced in the islets of Langerhans are insulin, glucagon, somatostatin, pancreatic polypeptide, and ghrelin.

The pancreatic hormones are secreted by alpha, beta, delta, gamma, and epsilon cells.

Key Terms

somatostatin: A polypeptide hormone, secreted by the pancreas, that inhibits the production of certain other hormones.

insulin: A polypeptide hormone that regulates carbohydrate metabolism.

glucagon: A hormone, produced by the pancreas, that opposes the action of insulin by stimulating the production of sugar.

Pancreatic Cells

The pancreas is a glandular organ that belongs to both the digestive and the endocrine systems of vertebrates. It is an endocrine gland that produces several important hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide.

It is also a digestive, exocrine organ, that secretes pancreatic juice that contains digestive enzymes to assist with digestion and the absorption of nutrients in the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.

Under a microscope, stained sections of the pancreas reveal two different types of parenchymal tissue. The light-stained clusters of cells are called islets of Langerhans, which produce hormones that underlie the endocrine functions of the pancreas.

The dark-stained cells form acini, connected to ducts. Acinar cells belong to the exocrine pancreas and secrete digestive enzymes into the gut via a system of ducts.

Islets of Langerhans

This is a microscope photograph of a porcine islet of Langerhans. On the left is a brightfield image created using hematoxylin stain; nuclei are dark circles and the acinar pancreatic tissue is darker than the islet tissue. The right image is the same section stained by immunofluorescence against insulin, indicating beta cells.

Islets of Langerhans: A porcine islet of Langerhans. On the left is a brightfield image created using hematoxylin stain; nuclei are dark circles and the acinar pancreatic tissue is darker than the islet tissue. The right image is the same section stained by immunofluorescence against insulin, indicating beta cells.

The pancreatic islets are small islands of cells that produce hormones that regulate blood glucose levels. Hormones produced in the pancreatic islets are secreted directly into the blood flow by five different types of cells. The endocrine cell subsets are:

  • Alpha cells produce glucagon and make up 15–20% of total islet cells. Glucagon is a hormone that raises blood glucose levels by stimulating the liver to convert its glycogen into glucose.
  • Beta cells produce insulin and amylin, and makeup 65–80% of the total islet cells. Insulin lowers blood glucose levels by stimulating cells to take up glucose out of the bloodstream. Amylin slows gastric emptying, preventing spikes in blood glucose levels.
  • Delta cells produce somatostatin and makeup 3–10% of the total islet cells. Somatostatin is a hormone that suppresses the release of the other hormones made in the pancreas.
  • Gamma cells produce pancreatic polypeptide and makeup 3–5% of the total islet cells. Pancreatic polypeptide regulates both the endocrine and exocrine pancreatic secretions.
  • Epsilon cells that produce ghrelin, and make up less than 1% of the total islet cells. Ghrelin is a protein that stimulates hunger.
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The islets of Langerhans can influence each other through paracrine and autocrine communication. The paracrine feedback system is based on the following correlations:

  • The insulin hormone activates beta cells and inhibits alpha cells.
  • The hormone glucagon activates alpha cells which then activate beta cells and delta cells.
  • Somatostatin hormone inhibits alpha cells and beta cells.

Insulin Secretion and Regulation of Glucagon

Glucagon is a peptide hormone that works in conjunction with insulin to maintain a stable blood glucose level.

Key Points

Glucagon and insulin are peptide hormones secreted by the pancreas that plays a key role in maintaining a stable blood glucose level.

Glucagon is produced by alpha cells in the pancreas and acts to raise blood sugar levels.

Insulin is produced by beta cells in the pancreas and acts to lower blood sugar levels.

Key Terms

insulin: A polypeptide hormone that regulates carbohydrate metabolism.

glycogen: A polysaccharide that is the main form of carbohydrate storage in animals and also converts to glucose as needed.

glucagon: A hormone, produced by the pancreas, that opposes the action of insulin by stimulating the production of sugar.

Glucagon and insulin are peptide hormones secreted by the pancreas that play a key role in maintaining a stable blood glucose level. The blood glucose level is carefully monitored by cells within the pancreas that respond by secreting key hormones.

Glucagon

This is an image from a microscope stained for glucagon.

Glucagon staining: This is an image from a microscope stained for glucagon.

Glucagon is produced by alpha cells in the pancreas and elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis. Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan.

Liver cells have glucagon receptors and when glucagon binds to the liver cells they convert glycogen into individual glucose molecules and release them into the bloodstream—this process is known as glycogenolysis. As these stores become depleted, glucagon then encourages the liver and kidney to synthesize additional glucose by gluconeogenesis. Glucagon also turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis that can induce lipolysis to produce glucose from fat.

Insulin

Insulin is produced by beta cells in the pancreas and acts to oppose the functions of glucagon. It’s main role is to promote the conversion of circulating glucose into glycogen via glycogenesis in the liver and muscle cells.

Insulin also inhibits
gluconeogenesis and promotes the storage of glucose in fat through lipid synthesis and also by inhibiting lipolysis.

In Disease

When control of insulin levels fails, diabetes mellitus can result. As a consequence, insulin is used medically to treat some forms of diabetes mellitus.

Patients with type 1 diabetes depend on external insulin (most commonly injected subcutaneously) for their survival because the hormone is no longer produced internally.

Patients with type 2 diabetes are often insulin resistant and, because of such resistance, they may suffer from a relative insulin deficiency. Some patients with type 2 diabetes may eventually require insulin if other medications fail to control blood glucose levels adequately.

Pancreatic enzymes

Your pancreas creates natural juices called pancreatic enzymes to break down foods. These juices travel through your pancreas via ducts. They empty into the upper part of your small intestine called the duodenum. Each day, your pancreas makes about 8 ounces of digestive juice filled with enzymes. These are the different enzymes:

  • Lipase. This enzyme works together with bile, which your liver produces, to break down fat in your diet. If you don’t have enough lipase, your body will have trouble absorbing fat and the important fat-soluble vitamins (A, D, E, K). Symptoms of poor fat absorption include diarrhea and fatty bowel movements.
  • Protease. This enzyme breaks down proteins in your diet. It also helps protect you from germs that may live in your intestines, like certain bacteria and yeast. Undigested proteins can cause allergic reactions in some people.
  • Amylase. This enzyme helps break down starches into sugar, which your body can use for energy. If you don’t have enough amylase, you may get diarrhea from undigested carbohydrates.

Pancreatic hormones

Many groups of cells produce hormones inside your pancreas. Unlike enzymes that are released into your digestive system, hormones are released into your blood and carry messages to other parts of your digestive system. Pancreatic hormones include:

  • Insulin. This hormone is made in cells of the pancreas known as beta cells. Beta cells make up about 75% of pancreatic hormone cells. Insulin is the hormone that helps your body use sugar for energy. Without enough insulin, your sugar levels rise in your blood and you develop diabetes.
  • Glucagon. Alpha cells make up about 20% of the cells in your pancreas that produce hormones. They produce glucagon. If your blood sugar gets too low, glucagon helps raise it by sending a message to your liver to release stored sugar.
  • Gastrin and amylin. Gastrin is primarily made in the G cells in your stomach, but some is made in the pancreas, too. It stimulates your stomach to make gastric acid. Amylin is made in beta cells and helps control appetite and stomach emptying.

Common pancreatic problems and digestion

Diabetes, pancreatitis, and pancreatic cancer are three common problems that affect the pancreas. Here is how they can affect digestion:

  • Diabetes. If your pancreatic beta cells do not produce enough insulin or your body can’t use the insulin your pancreas produces, you can develop diabetes. Diabetes can cause gastroparesis, a reduction in the motor function of the digestive system. Diabetes also affects what happens after digestion. If you don’t have enough insulin and you eat a meal high in carbohydrates, your sugar can go up and cause symptoms like hunger and weight loss. Over the long term, it can lead to heart and kidney disease among other problems.
  • Pancreatitis. Pancreatitis happens when the pancreas becomes inflamed. It is often very painful. In pancreatitis, the digestive enzymes your pancreas make attack your pancreas and cause severe abdominal pain. The main cause of acute pancreatitis is gall stones blocking the common bile duct. Too much alcohol can cause pancreatitis that does not clear up. This is known as chronic pancreatitis. Pancreatitis affects digestion because enzymes are not available. This leads to diarrhea, weight loss, and malnutrition. About 90% of the pancreas must stop working to cause these symptoms.
  • Pancreatic cancer. About 95% of pancreatic cancers begin in the cells that make enzymes for digestion. Not having enough pancreatic enzymes for normal digestion is very common in pancreatic cancer. Symptoms can include weight loss, loss of appetite, indigestion, and fatty stools.
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Your pancreas is important for digesting food and managing your use of sugar for energy after digestion. If you have any symptoms of pancreatic digestion problems, like loss of appetite, abdominal pain, fatty stools, or weight loss, call your healthcare provider.

Function

Pancreatic Hormones and Their Function[1][2][3]

Insulin

Source: Beta cells of islets of the pancreas.

Synthesis: Insulin is a peptide hormone. The insulin mRNA is translated as a single-chain precursor called preproinsulin, and removal of its signal peptide during insertion into the endoplasmic reticulum generates proinsulin. Within the endoplasmic reticulum, proinsulin is exposed to several specific endopeptidases, which excise the C peptide (one of three domains of proinsulin), thereby generating the mature form of insulin. Insulin is secreted from the cell by exocytosis and diffuses into islet capillary blood. C-peptide is also secreted into the blood in a 1:1 molar ratio with insulin. Although C-peptide has no established biological action, it is used as a useful marker for insulin secretion.

Transport: insulin circulates entirely in unbound form (T1/2 = 6 min).

Main Target cells: hepatic, muscle and adipocyte cells (i.e., cells specialized for energy storage).

Mechanism of action: Insulin binds to a specific receptor tyrosine kinase on the plasma membrane and increases its activity to phosphorylate numerous regulatory enzymes and other protein substrates.

Regulation of its secretion: Plasma glucose level is the main regulator of insulin secretion. The change in the concentration of plasma glucose that occurs in response to feeding or fasting is the main determinant of insulin secretion. Modest increases in plasma glucose level provoke a marked increase in plasma insulin concentration. Glucose is taken up by beta cells via glucose transporters (GLUT2). The subsequent metabolism of glucose increases cellular adenosine triphosphate (ATP) concentrations and closes ATP-dependent potassium (KATP) channels in the beta cell membrane, causing membrane depolarization and an influx of calcium. Increased calcium intracellular concentration results in an increase of insulin secretion. Increased plasma amino acid and free fatty acid concentrations induce insulin secretion as well. Glucagon is also known to be a strong insulin secretagogue.

Physiological functions: Insulin plays an important role to keep plasma glucose values within a relatively narrow range throughout the day (glucose homeostasis). Insulin’s main actions are

  • (1) In the liver, insulin promotes glycolysis and storage of glucose as glycogen (glycogenesis), as well as the conversion of glucose to triglycerides,
  • (2) In muscle, insulin promotes the uptake of glucose and its storage as glycogen, and
  • (3) in adipose tissue, insulin promotes the uptake of glucose and its conversion to triglycerides for storage.

Amylin (diabetes-associated peptide)

Source: Beta cells of islets of the pancreas. It is co-secreted with insulin in response to caloric intake (feeding state).

Target cells: Alpha cells of islets of pancreas and hypothalamus.

Physiological functions: it suppresses glucagon secretion from the alpha cells of the islets in the pancreas via paracrine interaction between beta cells and alpha cells. Amylin also slows gastric emptying which delays the absorption of glucose from the small intestine into the circulation. Also, it stimulates the satiety center of the brain to limit food consumption.

Glucagon

Source: Alpha cells of islets of the pancreas.

Synthesis: The initial gene product is the mRNA encoding preproglucagon. A peptidase removes the signal sequence of preproglucagon during translation of the mRNA in the rough endoplasmic reticulum to yield proglucagon. Proteases in the alpha cells subsequently cleave the proglucagon into the mature glucagon molecule.

Target cells: Hepatic cells.

Mechanism of action: glucagon binds to a receptor that activates the heterotrimeric G protein Gas, which stimulates membrane-bound adenylyl cyclase. The cAMP formed by adenylyl cyclase, in turn, activates PKA, which phosphorylates numerous regulatory enzymes and other protein substrates.

Regulation of its secretion: The amino acids released by digestion of a protein meal appear to be the main determinant of glucagon secretion.

Physiological functions: Glucagon acts exclusively on the liver to antagonize insulin effects on hepatocytes. It enhances glycogenolysis and gluconeogenesis. It also promotes the oxidation of fat, which can lead to the formation of ketone bodies.

Somatostatin

Source: Delta cells of the islets of the pancreas, hypothalamus, and D cells of gastric glands.

Target cells: Beta cells of islets of the pancreas, somatotroph cells in the anterior pituitary gland, and the G cells of the gastric glands.

Mechanism of action: Somatostatin binds to a receptor that activates the heterotrimeric inhibitory G protein, which inhibits membrane-bound adenylyl cyclase and cAMP formation.

Regulation of its secretion: Glucagon stimulates somatostatin secretion via paracrine interaction between alpha cells and delta cells of the islets of the pancreas.

Physiological functions: Somatostatin inhibits the secretion of multiple hormones, including growth hormone, insulin, glucagon, gastrin, vasoactive intestinal peptide (VIP), and thyroid-stimulating hormone.

Ghrelin

Source: Epsilon cells of the islets of the pancreas, endocrine cells in the stomach and hypothalamus.

Target cells: Beta cells of the islets of the pancreas and somatotroph cells in the anterior pituitary gland.

Physiological functions:  ghrelin inhibits the secretion of insulin from Beta cells of the islets of the pancreas via paracrine interaction between delta cells and beta cells of the islets of the pancreas. It also stimulates appetite and growth hormone secretion.

Pancreatic Polypeptide (PP)

Pancreatic polypeptide is secreted from upsilon (F) cells of the islets of the pancreas. Dietary intake of nutrients alters the secretion of the pancreatic polypeptide. Its function is not decidedly understood yet.

Paracrine Interaction Between Pancreatic Endocrine Cells

Insulin secreted by beta cells acts as a prime hormone of glucose homeostasis. Insulin and amylin inhibit glucagon secretion by alpha cells. Whereas glucagon activates insulin and somatostatin secretion, somatostatin secreted by delta cells and ghrelin by epsilon cells inhibits insulin secretion.

WHY IS THIS IMPORTANT?

Understanding the two functions of the pancreas is important because

Large tumors of the pancreas will interfere with both of these important bodily functions.

  • Exocrine: when tumors block the exocrine system, patients can develop pancreatitis and pain from the abnormal release of digestive enzymes into the substance of the pancreas instead of into the bowel, and they can develop digestive problems, such as diarrhea, from the incomplete digestion of food.
  • Endocrine: when tumors destroy the endocrine function of the pancreas, patients can develop sugar diabetes (abnormally high blood sugar levels).

Tumors can arise in either component, exocrine or endocrine.

  • Exocrine: the vast majority of tumors of the pancreas arise in the exocrine part and these cancers look like pancreatic ducts under the microscope. These tumors are therefore called ductal adenocarcinomas, or simply adenocarcinoma, or even more simply pancreatic cancer.
  • Endocrine: less commonly, tumors arise from the endocrine component of the pancreas and these endocrine tumors are called “pancreatic neuroendocrine tumors,” or “islet cell tumors” for short.

References

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