The pancreas (plural pancreases or pancreata) is a crucial organ integral to both the digestive and endocrine systems of vertebrates. In humans, it is located in the abdomen, posterior to the stomach, functioning as a gland. This organ is classified as a mixed or heterocrine gland, possessing distinct endocrine and exocrine capabilities. Approximately ninety-nine percent of the pancreas is dedicated to exocrine functions, while one percent serves endocrine roles. As an endocrine gland, its primary responsibility is the regulation of blood sugar levels through the secretion of hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide. Conversely, its exocrine function within the digestive system involves secreting pancreatic juice into the duodenum via the pancreatic duct. This juice contains bicarbonate, which neutralizes gastric acid entering the duodenum, and digestive enzymes vital for the breakdown of carbohydrates, proteins, and fats from food.
The pancreas (plural pancreases, or pancreata) 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 is a mixed or heterocrine gland, i.e., it has both an endocrine and a digestive exocrine function. Ninety-nine percent of the pancreas is exocrine and 1% is endocrine. 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.
Inflammation of the pancreas is medically termed pancreatitis, with common etiologies including chronic alcohol consumption and gallstones. Due to its critical function in blood sugar regulation, the pancreas is also a pivotal organ in the pathology of diabetes. Pancreatic cancer, which can develop following chronic pancreatitis or from other causes, generally carries a very poor prognosis, as it is frequently diagnosed only after it has metastasized to other regions of the body.
The etymology of the term 'pancreas' originates from the Greek words πᾶν (pân, meaning 'all') and κρέας (kréas, meaning 'flesh'). The pancreatic involvement in diabetes was recognized as early as 1889, with its specific role in insulin production being elucidated in 1921.
Anatomical Structure
In humans, the pancreas is an abdominal organ extending from its position posterior to the stomach towards the left upper abdomen, in proximity to the spleen. In adult individuals, it typically measures approximately 12–15 centimeters (4.7–5.9 inches) in length, exhibiting a lobulated morphology and a characteristic salmon coloration.
Anatomically, the pancreas is segmented into four principal regions: the head, neck, body, and tail. The organ originates at the inner curvature of the duodenum, where its head encircles the superior mesenteric artery and vein. The body, representing the longest segment of the pancreas, extends transversely posterior to the stomach, while the tail terminates in close proximity to the spleen.
The pancreatic ductal system comprises two primary conduits: the main pancreatic duct and a smaller accessory pancreatic duct, both traversing the pancreatic body. The main pancreatic duct converges with the common bile duct to form a dilated structure known as the ampulla of Vater (or hepatopancreatic ampulla). This ampulla is enveloped by a muscular valve, the sphincter of Oddi, and subsequently opens into the descending segment of the duodenum. The entry of the common bile duct into the main pancreatic duct is regulated by the sphincter of Boyden. The accessory pancreatic duct possesses distinct openings into the duodenum, situated superior to the orifice of the main pancreatic duct.
Pancreatic Regions
The head of the pancreas is positioned within the duodenal curvature, encircling the superior mesenteric artery and vein. Laterally to its right lies the descending portion of the duodenum, with the superior and inferior pancreaticoduodenal arteries traversing the space between them. Posteriorly, the head is contiguous with the inferior vena cava and the common bile duct. Anteriorly, it is covered by the peritoneal membrane and the transverse colon. A distinct uncinate process projects inferiorly from the head, situated posterior to the superior mesenteric vein and occasionally the superior mesenteric artery. The pancreatic notch delineates the boundary between the pancreatic neck and the uncinate process.
The neck of the pancreas serves as a transitional segment, separating the pancreatic head, which resides within the duodenal curvature, from the pancreatic body. This region measures approximately 2 centimeters (0.79 inches) in width and is situated anterior to the confluence forming the portal vein. Primarily located posterior to the pylorus of the stomach, the neck is largely enveloped by the peritoneum. The anterior superior pancreaticoduodenal artery courses anterior to the pancreatic neck.
The body of the pancreas, the largest segment of the organ, is primarily situated posterior to the stomach and gradually attenuates along its longitudinal axis. The peritoneum is positioned superior to the pancreatic body, with the transverse colon located anterior to the peritoneum. Posterior to the pancreas lie several crucial blood vessels, including the aorta, the splenic vein, the left renal vein, and the proximal portion of the superior mesenteric artery. Inferior to the pancreatic body are located segments of the small intestine, specifically the terminal segment of the duodenum and its contiguous jejunum, along with the suspensory ligament of the duodenum interposed between these structures.
The pancreas attenuates into the tail of the pancreas, which is situated in proximity to the spleen. Typically measuring between 1.3–3.5 cm (0.51–1.38 in) in length, it is enveloped within the layers of the ligament connecting the spleen and the left kidney. The splenic artery and vein traverse posterior to both the body and tail of the pancreas.
Blood Supply
The pancreas exhibits extensive vascularization, with vessels derived from branches of both the celiac artery and the superior mesenteric artery. The splenic artery, which is the largest branch of the celiac trunk, courses superior to the pancreas and vascularizes the left aspect of the body and the pancreatic tail via its pancreatic ramifications, notably including the greater pancreatic artery. The superior and inferior pancreaticoduodenal arteries traverse the posterior and anterior surfaces of the pancreatic head in close proximity to the duodenum. These vessels provide arterial supply to the pancreatic head and form anastomoses centrally.
The body and neck of the pancreas are drained by the splenic vein, which is situated posterior to the organ. The pancreatic head drains into and encircles the superior mesenteric and portal veins through the pancreaticoduodenal veins.
The pancreas possesses an extensive lymphatic drainage system, with vessels accompanying its arterial supply. Lymphatic drainage from the pancreatic body and tail converges into splenic lymph nodes, ultimately progressing to pre-aortic lymph nodes situated between the celiac and superior mesenteric arteries. Conversely, the lymphatic vessels of the head and neck empty into intermediate lymphatic channels surrounding the pancreaticoduodenal, mesenteric, and hepatic arteries, subsequently reaching the pre-aortic lymph nodes.
Microanatomy
The pancreas comprises tissues performing both endocrine and exocrine functions. This functional dichotomy is discernible upon microscopic examination of pancreatic tissue.
The predominant pancreatic tissue component is dedicated to digestive functions. These cells aggregate into clusters, known as acini, which encircle small ducts and are organized into lobules demarcated by slender fibrous septa. The cells of each acinus excrete inactive digestive enzymes, termed zymogens, into the small intercalated ducts that they encompass. Within each acinus, the cells exhibit a pyramidal morphology, arrayed around the intercalated ducts, characterized by nuclei positioned on the basement membrane, an extensive endoplasmic reticulum, and numerous zymogen granules discernible within their cytoplasm. These intercalated ducts subsequently converge into larger intralobular ducts within each lobule, ultimately leading to interlobular ducts. Initially, the ducts are lined by a single layer of columnar epithelial cells; however, as ductal diameter increases, the epithelial lining becomes multilayered.
Pancreatic tissues with an endocrine function are organized into discrete cellular clusters known as pancreatic islets (or islets of Langerhans), which are disseminated throughout the organ. These islets comprise alpha, beta, and delta cells, each type responsible for secreting distinct hormones. A characteristic spatial arrangement is observed, with alpha cells (secreting glucagon) typically localized to the islet periphery, while the more abundant beta cells (secreting insulin) are distributed throughout the islet core. Additionally, enterochromaffin cells are interspersed within the islet parenchyma. Each islet may consist of up to 3,000 secretory cells and is vascularized by multiple small arterioles for blood supply, alongside venules facilitating the entry of secreted hormones into the systemic circulation.
Variation
The pancreas exhibits significant variability in size. Anatomical variations are common, stemming from the embryological development of its two distinct pancreatic buds. These buds originate on opposing sides of the duodenum during pancreatic formation. The ventral bud subsequently rotates to an adjacent position relative to the dorsal bud, ultimately undergoing fusion. Approximately 10% of adults may possess an accessory pancreatic duct, which persists if the primary duct of the dorsal pancreatic bud fails to regress; this accessory duct typically drains into the minor duodenal papilla. Should the two pancreatic buds, each equipped with its own duct, fail to fuse, the pancreas may develop with two distinct duct systems, a condition termed pancreas divisum. This anatomical variation generally presents no physiological ramifications. In instances where the ventral bud's rotation is incomplete, an annular pancreas can form, characterized by the encirclement of a segment or the entirety of the duodenum by pancreatic tissue. This anomaly can be correlated with duodenal atresia.
Gene and Protein Expression
Approximately 10,000 protein-coding genes, constituting about 50% of the total human genome, are expressed within the normal human pancreas. Of these, fewer than 100 genes exhibit pancreas-specific expression. Analogous to salivary glands, the majority of pancreas-specific genes transcribe proteins destined for secretion. These pancreas-specific proteins are either synthesized within the exocrine cellular compartment, performing roles in digestion and nutrient assimilation, exemplified by digestive chymotrypsinogen enzymes and pancreatic lipase PNLIP, or they are produced by the diverse cell types within the endocrine pancreatic islets, where they function as secreted hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide.
Development
During embryonic development, the pancreas originates from two pancreatic buds that emerge from the duodenal segment of the foregut, an embryonic tube that serves as a precursor to the gastrointestinal tract. Its cellular lineage is endodermal. Pancreatic morphogenesis commences with the differentiation of distinct dorsal and ventral pancreatic buds. Each bud establishes a connection with the foregut via a dedicated duct. The dorsal pancreatic bud subsequently differentiates into the neck, body, and tail of the mature pancreas, while the ventral pancreatic bud gives rise to the head and uncinate process.
The formation of the definitive pancreas is contingent upon the rotation of the ventral bud and the subsequent fusion of both pancreatic buds. As development progresses, the duodenum undergoes a rightward rotation, carrying the ventral bud along with it to a more dorsal anatomical position. Once positioned, the ventral pancreatic bud lies inferior to the larger dorsal bud, ultimately fusing with it. This fusion point facilitates the coalescence of the primary ducts from both ventral and dorsal pancreatic buds, thereby establishing the main pancreatic duct. Typically, the duct of the dorsal bud undergoes regression, leaving the main pancreatic duct as the predominant drainage pathway.
Cellular Development
Pancreatic progenitor cells represent precursor cells capable of differentiating into the various functional cell types of the pancreas, encompassing exocrine centroacinar cells, endocrine islet cells, and ductal cells. These progenitor cells are distinguished by the concurrent expression of the transcription factors PDX1 and NKX6-1.
Exocrine pancreatic cells undergo differentiation influenced by specific inducing molecules, such as follistatin, fibroblast growth factors, and the activation of the Notch receptor system. The morphogenesis of exocrine acini proceeds through three sequential stages. These stages are designated as predifferentiated, protodifferentiated, and differentiated, correlating respectively with undetectable, low, and high levels of digestive enzyme activity.
Pancreatic progenitor cells differentiate into endocrine islet cells under the regulatory influence of neurogenin-3 and ISL1, a process contingent upon the absence of Notch receptor signaling. Guided by a Pax gene, endocrine precursor cells differentiate into alpha and gamma cells. Conversely, under the influence of Pax-6, these endocrine precursor cells develop into beta and delta cells. Pancreatic islets are formed as endocrine cells migrate from the ductal system to aggregate into small clusters adjacent to capillaries. This developmental event typically transpires around the third month of gestation, with insulin and glucagon becoming detectable in the human fetal circulation by the fourth or fifth month of development.
Function
The pancreas plays a dual role in the body, contributing to both blood glucose regulation and metabolic processes, as well as secreting pancreatic juice, which aids digestion. These functions are categorized into an endocrine capacity, involving the release of insulin and other hormones from pancreatic islets to manage blood sugar and metabolism, and an exocrine capacity, focused on the secretion of digestive enzymes.
Blood Glucose Regulation
Pancreatic cells are instrumental in maintaining blood glucose homeostasis. These specialized cells reside within the pancreatic islets, which are distributed throughout the organ. The regulation of blood glucose involves the following mechanisms:
- In response to diminished blood glucose concentrations, alpha cells release glucagon, thereby elevating systemic glucose levels.
- Conversely, when blood glucose levels are elevated, beta cells secrete insulin, which acts to reduce circulating glucose.
Additionally, delta cells within the islets produce somatostatin, a hormone that modulates and diminishes the secretion of both insulin and glucagon.
Glucagon functions to elevate glucose concentrations by stimulating hepatic gluconeogenesis and glycogenolysis, the breakdown of glycogen into glucose within the liver. Furthermore, it reduces glucose uptake by adipose and muscle tissues. The secretion of glucagon is triggered by low blood glucose or insulin levels, and it is also stimulated during physical exertion.
Insulin functions to lower blood glucose by facilitating its cellular uptake, especially by skeletal muscle, and by promoting its utilization in the synthesis of proteins, lipids, and carbohydrates. Insulin is initially synthesized as preproinsulin, a precursor molecule. This is subsequently converted to proinsulin and then cleaved by C-peptide to yield active insulin, which is stored in granules within beta cells. Glucose entry into beta cells and its subsequent degradation lead to depolarization of the cell membrane, which in turn stimulates insulin secretion.
The primary determinant influencing the secretion of both insulin and glucagon is the concentration of glucose in blood plasma; hypoglycemia stimulates glucagon release, while hyperglycemia prompts insulin secretion. Additional factors also modulate the release of these hormones. Certain amino acids, generated during protein digestion, can stimulate both insulin and glucagon secretion. Somatostatin functions as an inhibitory agent for both insulin and glucagon. The autonomic nervous system also exerts influence; activation of beta-2 receptors by catecholamines from sympathetic nerves stimulates the release of both insulin and glucagon, whereas alpha-1 receptor activation inhibits their secretion. Furthermore, M3 receptors of the parasympathetic nervous system, when stimulated by the right vagus nerve, promote insulin release from beta cells.
Digestion
The pancreas performs a crucial function within the digestive system by secreting pancreatic juice, an enzyme-rich fluid, directly into the duodenum, the initial segment of the small intestine that receives chyme from the stomach. These enzymes are essential for the catabolism of carbohydrates, proteins, and lipids. This constitutes the exocrine function of the pancreas. The specialized cells responsible for this secretion are centroacinar cells, organized into glandular clusters known as acini. Secretions from the central lumen of each acinus collect in intralobular ducts, which subsequently converge into the main pancreatic duct, ultimately emptying into the duodenum. Approximately 1.5 to 3 liters of this fluid are secreted daily.
Within each acinus, cells are replete with granules containing digestive enzymes. These enzymes are initially secreted in an inactive precursor form, known as zymogens or proenzymes. Upon their release into the duodenum, they undergo activation by enterokinase, an enzyme found in the duodenal lining. This cleavage of proenzymes initiates a cascade of enzymatic activation.
- The proteolytic enzymes, responsible for protein degradation, are activated commencing with the conversion of trypsinogen to trypsin. Subsequently, the liberated trypsin catalyzes the cleavage of remaining trypsinogen, as well as chymotrypsinogen, into its active form, chymotrypsin.
- Enzymes secreted for the digestion of lipids include lipase, phospholipase A2, lysophospholipase, and cholesterol esterase.
- Amylase is among the enzymes responsible for the breakdown of starch and other carbohydrates.
These enzymes are secreted within a bicarbonate-rich fluid, which maintains an alkaline pH optimal for most enzymatic activity and neutralizes gastric acids entering the duodenum. Hormone regulation, including secretin, cholecystokinin, and vasoactive intestinal peptide (VIP), along with acetylcholine stimulation from the vagus nerve, influences this secretion. Secretin is released from duodenal S cells in response to gastric acid, and in conjunction with VIP, it enhances enzyme and bicarbonate secretion. Cholecystokinin, primarily released from Ito cells in the duodenal and jejunal lining due to long-chain fatty acids, amplifies the effects of secretin. At a cellular level, bicarbonate is secreted from centroacinar and ductal cells via a sodium-bicarbonate cotransporter, activated by membrane depolarization induced by the cystic fibrosis transmembrane conductance regulator. Secretin and VIP promote the opening of this regulator, leading to increased membrane depolarization and subsequent bicarbonate secretion.
Various mechanisms are in place to prevent the pancreas's digestive enzymes from damaging its own tissue. These include the secretion of inactive enzyme precursors (zymogens), the release of the protective trypsin inhibitor which deactivates trypsin, pH changes associated with bicarbonate secretion that activate digestion only when the pancreas is stimulated, and the inactivation of trypsin due to low intracellular calcium concentrations.
Additional Functions
The pancreas also secretes vasoactive intestinal peptide and pancreatic polypeptide. Enterochromaffin cells within the pancreas produce the hormones motilin, serotonin, and substance P. Research has demonstrated that pancreatic tissue effectively accumulates and secretes radioactive cesium (Cs-137) into the intestine.
Clinical Significance
Inflammation
Pancreatitis refers to inflammation of the pancreas, most frequently linked to recurrent gallstones or chronic alcohol consumption. Other common etiologies include traumatic injury, complications following endoscopic retrograde cholangiopancreatography (ERCP), certain medications, infections such as mumps, and extremely elevated blood triglyceride levels. Acute pancreatitis typically manifests as severe pain in the central abdomen, often radiating to the back, and may be accompanied by nausea or vomiting. Severe cases can result in hemorrhage or pancreatic perforation, leading to shock or systemic inflammatory response syndrome, and bruising in the flanks or around the umbilicus. Such critical complications often necessitate management in an intensive care unit.
In pancreatitis, the exocrine pancreatic enzymes cause damage to the pancreatic structure and tissue. The detection of these enzymes, such as amylase and lipase, in the bloodstream, combined with characteristic symptoms and findings from medical imaging like ultrasound or CT scans, frequently indicates a diagnosis of pancreatitis. Medical management typically involves pain relief, monitoring to prevent or treat shock, and addressing any identified underlying causes. This may include the removal of gallstones, reduction of blood triglyceride or glucose levels, corticosteroid use for autoimmune pancreatitis, and the discontinuation of any triggering medications.
Chronic pancreatitis involves the progressive development of pancreatic inflammation over time. It shares many causes with acute pancreatitis, with chronic alcohol use being the most prevalent, alongside recurrent acute episodes and cystic fibrosis. Abdominal pain, characteristically alleviated by sitting forward or consuming alcohol, is the most common symptom. Severe impairment of the pancreas's digestive function can lead to fat maldigestion and steatorrhea, while compromised endocrine function may result in diabetes. Chronic pancreatitis is investigated similarly to acute pancreatitis. In addition to managing pain and nausea, and addressing identified causes (which may include alcohol cessation), enzyme replacement therapy may be necessary to prevent malabsorption due to the pancreas's digestive role.
Cancer
Pancreatic cancers, particularly pancreatic adenocarcinoma, the most prevalent subtype, present significant therapeutic challenges and are frequently identified at advanced stages, precluding surgical intervention, which is the sole potentially curative modality. Pancreatic cancer is infrequent in individuals under 40 years of age, with a median diagnostic age of 71 years. Associated risk factors encompass chronic pancreatitis, advanced age, smoking, obesity, diabetes, and specific rare genetic predispositions, such as multiple endocrine neoplasia type 1, hereditary nonpolyposis colon cancer, and dysplastic nevus syndrome. Approximately 25% of diagnoses are linked to tobacco use, with 5–10% attributed to inherited genetic factors.
Pancreatic adenocarcinoma, the predominant subtype of pancreatic malignancy, originates from the exocrine digestive tissue of the pancreas. The majority of cases manifest in the pancreatic head. Clinical manifestations typically emerge at advanced disease stages, presenting as abdominal discomfort, unexplained weight loss, or icterus (jaundice). Icterus results from biliary obstruction caused by the tumor. Less frequent symptoms may encompass nausea, emesis, pancreatitis, new-onset diabetes, or recurrent venous thrombosis. Diagnosis of pancreatic cancer commonly relies on medical imaging, specifically ultrasound or contrast-enhanced CT scans. Endoscopic ultrasound may be employed for tumors being evaluated for surgical resection, and biopsy guided by endoscopic retrograde cholangiopancreatography (ERCP) or ultrasound can corroborate an equivocal diagnosis.
The delayed onset of symptoms typically results in the presentation of most cancers at an advanced stage. Consequently, only 10% to 15% of tumors are amenable to surgical resection. As of 2018, the FOLFIRINOX chemotherapy regimen, comprising fluorouracil, irinotecan, oxaliplatin, and leucovorin, has demonstrated improved survival outcomes compared to conventional gemcitabine-based treatments. Predominantly, treatment is palliative, concentrating on managing emergent symptoms. Palliative interventions may involve addressing pruritus, performing a choledochojejunostomy, inserting stents via ERCP to restore bile drainage, and administering pharmacotherapy for pain management. In the United States, pancreatic cancer ranks as the fourth leading cause of cancer-related mortality. The incidence of this disease is higher in developed nations, accounting for 68% of new cases in 2012. Pancreatic adenocarcinoma is generally associated with unfavorable prognoses, with average one-year and five-year survival rates post-diagnosis being 25% and 5%, respectively. For localized disease, specifically tumors smaller than 2 cm, the five-year survival rate is approximately 20%.
Pancreatic cancer encompasses various types, affecting both endocrine and exocrine tissues. Numerous forms of pancreatic endocrine tumors exist, all of which are uncommon or rare, presenting diverse prognoses. Nevertheless, the incidence of these malignancies has significantly increased; the extent to which this trend reflects enhanced detection, particularly via medical imaging, of indolent tumors remains uncertain. Insulinomas (predominantly benign) and gastrinomas represent the most frequently encountered types. Patients diagnosed with neuroendocrine cancers exhibit a substantially improved five-year survival rate of 65%, though this varies considerably by specific tumor type.
A solid pseudopapillary tumor is characterized as a low-grade malignant pancreatic neoplasm with a papillary architecture, predominantly affecting young women.
Diabetes Mellitus
Type 1 Diabetes
Type 1 diabetes mellitus is a chronic autoimmune disorder characterized by the immune system's destruction of the insulin-producing beta cells within the pancreas. Insulin is essential for maintaining optimal blood glucose levels; its deficiency results in hyperglycemia. If left untreated, this chronic condition can lead to complications such as accelerated vascular disease, diabetic retinopathy, nephropathy, and neuropathy. Furthermore, insufficient insulin for cellular glucose utilization can precipitate diabetic ketoacidosis, a medical emergency frequently presenting as the initial symptom of type 1 diabetes. While type 1 diabetes can manifest at any age, diagnosis most commonly occurs before 40 years of age. For individuals with type 1 diabetes, exogenous insulin administration is vital for survival. Experimental therapeutic approaches for type 1 diabetes include whole pancreas transplantation or isolated islet cell transplantation, aiming to provide the recipient with functional beta cells.
Type 2 Diabetes
Type 2 diabetes mellitus represents the most prevalent form of diabetes. Elevated blood glucose levels in this condition typically result from a confluence of insulin resistance and diminished insulin secretion, with both genetic predispositions and environmental influences contributing to its pathogenesis. Progressively, pancreatic beta cells can experience functional decline and exhaustion. Therapeutic strategies for type 2 diabetes encompass lifestyle modifications, pharmacological interventions when necessary, and potentially insulin therapy. Regarding pancreatic function, several medications are designed to augment insulin secretion from beta cells. These include sulfonylureas, which directly stimulate beta cells; incretins, which mimic the effects of glucagon-like peptide 1 hormones, thereby increasing post-prandial insulin secretion from beta cells and exhibiting greater resistance to degradation; and DPP-4 inhibitors, which impede the breakdown of incretins.
Removal
Individuals can sustain life without a pancreas, contingent upon consistent insulin administration for precise blood glucose regulation and the intake of pancreatic enzyme supplements to facilitate digestion.
History
The pancreas was initially identified by Herophilus (335–280 BC), a Greek anatomist and surgeon. Centuries later, Rufus of Ephesus, another Greek anatomist, bestowed its current name upon the organ. Etymologically, "pancreas" derives from the modern Latin adaptation of the Greek term πάγκρεας, combining πᾶν ("all" or "whole") and κρέας ("flesh"). While literally translating to "all-flesh," likely due to its fleshy texture, the term originally referred to sweetbread. A pivotal discovery occurred in 1889 when Oskar Minkowski observed that pancreatectomy in dogs induced diabetes. Subsequently, in 1921, Frederick Banting and Charles Best successfully isolated insulin from pancreatic islets.
Methodologies for examining pancreatic tissue have evolved significantly. Historically, observation relied on basic staining techniques, such as hematoxylin and eosin (H&E) stains. Currently, immunohistochemistry offers a more precise approach for differentiating cell types. This technique utilizes visible antibodies targeting specific cellular products, thereby facilitating the identification of distinct cell populations, including alpha and beta cells.
Other Animals
Pancreatic tissue is ubiquitous across all vertebrate species, though its specific morphology and anatomical organization exhibit considerable variation. Some species may possess up to three distinct pancreases, with two originating from the pancreatic bud and one developing dorsally. In the majority of species, including humans, these structures typically fuse during adulthood; however, notable exceptions exist. Even in cases where a single pancreas is present, two or three pancreatic ducts may persist, each independently draining into the duodenum or its equivalent foregut segment. Avian species, for instance, commonly feature three such ducts.
In teleost fish and certain other species, such as rabbits, a discrete pancreas is entirely absent. Instead, pancreatic tissue is diffusely dispersed throughout the mesentery and occasionally within adjacent organs like the liver or spleen. While some teleost species exhibit a fusion of endocrine tissue into a distinct gland within the abdominal cavity, it is otherwise distributed among the exocrine components. The most rudimentary arrangement, however, is observed in lampreys and lungfish, where pancreatic tissue manifests as multiple discrete nodules embedded within the gut wall, with the exocrine elements closely resembling other intestinal glandular structures.
Cuisine
The pancreas from calves (ris de veau) or lambs (ris d'agneau), and less frequently from beef or pork, is consumed as a food item known culinarily as sweetbread.
References
Barrett, Kim E. (2019). Ganong's Review of Medical Physiology. Barman, Susan M., Brooks, Heddwen L., Yuan, Jason X.-J. (26th ed.). New York. ISBN 978-1-260-12240-4. OCLC 1076268769.{{cite book}}: CS1 maint: location missing publisher (link)
- Barrett, Kim E. (2019). Ganong's review of medical physiology. Barman, Susan M.,, Brooks, Heddwen L., Yuan, Jason X.-J. (26th ed.). New York. ISBN 978-1-260-12240-4. OCLC 1076268769.{{cite book}}: CS1 maint: location missing publisher (link)
- Beger HG, ed. (2018). The Pancreas: An Integrated Textbook of Basic Science, Medicine, and Surgery (third ed.). Hoboken, NJ. ISBN 978-1-119-18841-4. OCLC 1065547789.{{cite book}}: CS1 maint: location missing publisher (link)
- Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J (2015). Harrison's Principles of Internal Medicine (19th ed.). McGraw-Hill Professional. ISBN 978-0-07-180215-4.
- Standring, S., Borley, N. R., et al. (Eds.). (2008). Gray's Anatomy: The Anatomical Basis of Clinical Practice (40th ed.). London: Churchill Livingstone. ISBN 978-0-8089-2371-8.
{{cite book}}: CS1 maint: location missing publisher (link) - Young, B., O'Dowd, G., & Woodford, P. (2013). Wheater's Functional Histology: A Text and Colour Atlas (6th ed.). Philadelphia: Elsevier. ISBN 978-0-7020-4747-3.
- Pancreas at the Human Protein Atlas
- Pancreatic Diseases – English – The Gastro Specialist