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Pancreas: Anatomy

The pancreas lies mostly posterior to the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy and extends across the posterior abdominal wall Abdominal wall The outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum. Surgical Anatomy of the Abdomen from the duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy on the right to the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy on the left. The pancreas is covered with a very thin connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides that extends inward as septa, partitioning the gland into lobules Lobules Breasts: Anatomy. This organ has both exocrine and endocrine tissue. The exocrine portion is organized in grape-like clusters of acini, which are small sacs surrounding the terminal ends of pancreatic ducts. The cells lining the acini and ducts secrete products that make up pancreatic juices, which play a major role in digestion Digestion Digestion refers to the process of the mechanical and chemical breakdown of food into smaller particles, which can then be absorbed and utilized by the body. Digestion and Absorption. The endocrine portion of the gland consists of circular islets interspersed between acini, which secrete glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions, insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin, and somatostatin Somatostatin A 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal. Gastrointestinal Secretions.

Last updated: Mar 9, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Development

The pancreas is a leaf-shaped organ that lies transversely on the posterior abdominal wall Abdominal wall The outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum. Surgical Anatomy of the Abdomen

Gross Anatomy

Structure and anatomic relations

The pancreas is a leaf-shaped organ with 5 major parts:

  • Head:
    • Right lateral end of the pancreas
    • Lies within the C-shaped concavity of the duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy
    • Contains the main pancreatic duct and the common bile Bile An emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum. Gallbladder and Biliary Tract: Anatomy duct
    • Most common location for pancreatic malignancies
    • Uncinate process of the head: 
      • End of the pancreatic head that curves down, back, and medially to form a hook-like process
      • Posterior to the superior mesenteric vessels
  • Neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess
    • Relatively short region connecting the head to the body
    • Splenic vein runs posterior to the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, where it joins with the superior mesenteric vein (SMV), forming the hepatic portal Hepatic portal Liver: Anatomy vein.
  • Body: 
    • Elongated portion of the organ extending from the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess to the tail
    • Lies transversely along the posterior abdominal wall Abdominal wall The outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum. Surgical Anatomy of the Abdomen at the level of the L1–L2 vertebrae
    • Posterior to the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy
  • Tail: 
    • Left lateral end of the organ
    • Lies in front of the left kidney 
    • “Points toward” the hilum Hilum Lungs: Anatomy of the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy within the splenorenal ligament Splenorenal ligament Spleen: Anatomy
  • Note: The SMA and SMV/hepatic veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology run posterior to the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess/body but anterior to the uncinate process
Anatomic relationships of the pancreas to surrounding organs

Anatomic relationships of the pancreas to surrounding organs:
Note that the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy and stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy are light gray and that the intestines have been removed completely in order to allow better visualization of this posterior organ.

Image by BioDigital, edited by Lecturio

Ducts

The exocrine glands Exocrine glands Glands of external secretion that release its secretions to the body’s cavities, organs, or surface, through a duct. Glandular Epithelium: Histology within the pancreas secrete their products into a network of ducts. These ducts ultimately drain into the main pancreatic duct.

  • Main pancreatic duct (Wirsung duct): 
    • Combines with the common bile Bile An emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum. Gallbladder and Biliary Tract: Anatomy duct at the hepatopancreatic ampulla (i.e., ampulla of Vater)
    • Ampulla enters the descending part of the duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy at the major duodenal papilla:
      • Contains the hepatopancreatic sphincter (i.e., sphincter of Oddi) 
      • Sphincter regulates the secretion Secretion Coagulation Studies of bile Bile An emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum. Gallbladder and Biliary Tract: Anatomy and pancreatic fluid into the intestines.
      • Controlled by the autonomic nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. Nervous System: Anatomy, Structure, and Classification
  • Accessory pancreatic duct (duct of Santorini): 
    • A branch off the main pancreatic duct
    • Empties into the duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy at the minor duodenal papilla (located just above the major duodenal papilla)
    • Allows pancreatic juice to be released into the duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy even when bile Bile An emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum. Gallbladder and Biliary Tract: Anatomy is not

Microscopic Anatomy and Function

There are 2 primary functional and histologic tissue types in the pancreas. The exocrine pancreas secretes digestive enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes into the intestinal lumens, and the endocrine pancreas secretes hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types into the bloodstream.

Exocrine pancreas

Exocrine secretions are secretions into a lumen; in the case of the exocrine pancreas, its products, collectively known as pancreatic juices, are secreted into the intestinal lumen via the pancreatic duct. 

General structure:

  • Makes up approximately 80%–90% of the organ’s tissue
  • Made of up grape-like clusters of acini: 
    • Functional units of exocrine pancreas
    • Form small sacs around terminal ends of pancreatic ducts
    • Made up of centroacinar cells, which:
      • Produce and secrete enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes and zymogens into these small ducts
      • Have dense granules Dense granules Hemostasis at their apical ends (containing secretory products)
  • Ducts made up of columnar epithelial cells
  • Pancreas divided into lobules Lobules Breasts: Anatomy by septae ( connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology)

Pancreatic juice:

The fluid secreted into the ducts consists of:

  • Water and electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes
  • Enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes:
    • Pancreatic amylase Amylase A group of amylolytic enzymes that cleave starch, glycogen, and related alpha-1, 4-glucans. Digestion and Absorption → digests starch by breaking bonds in polysaccharides Polysaccharides Basics of Carbohydrates
    • Pancreatic lipase Lipase An enzyme of the hydrolase class that catalyzes the reaction of triacylglycerol and water to yield diacylglycerol and a fatty acid anion. It is produced by glands on the tongue and by the pancreas and initiates the digestion of dietary fats. Malabsorption and Maldigestion → digests fat by hydrolysis Hydrolysis The process of cleaving a chemical compound by the addition of a molecule of water. Proteins and Peptides
    • Ribonuclease Ribonuclease Enzymes that catalyze the hydrolysis of ester bonds within RNA. Interferons and deoxyribonuclease Deoxyribonuclease Enzymes which catalyze the hydrolases of ester bonds within DNA. Staphylococcus → degrades RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure and DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure, respectively
  • Zymogens ( enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes that are altered after secretion Secretion Coagulation Studies to become active): 
    • Functions: digest proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis
    • Zymogens secreted by the exocrine pancreas:
      • Trypsinogen Trypsinogen The inactive proenzyme of trypsin secreted by the pancreas, activated in the duodenum via cleavage by enteropeptidase. Pancreatic Parameters trypsin Trypsin A serine endopeptidase that is formed from trypsinogen in the pancreas. It is converted into its active form by enteropeptidase in the small intestine. It catalyzes hydrolysis of the carboxyl group of either arginine or lysine. Proteins and Peptides 
      • Chymotrypsinogen → chymotrypsin Chymotrypsin A serine endopeptidase secreted by the pancreas as its zymogen, chymotrypsinogen and carried in the pancreatic juice to the duodenum where it is activated by trypsin. It selectively cleaves aromatic amino acids on the carboxyl side. Pancreatic Parameters 
      • Procarboxypeptidase → carboxypeptidase Carboxypeptidase Enzymes that act at a free c-terminus of a polypeptide to liberate a single amino acid residue. Pancreatic Parameters
  • Sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia bicarbonate Bicarbonate Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the ph of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity. Electrolytes:
    • Secreted by ductal epithelial cells
    • Neutralizes hydrochloric acid Hydrochloric acid A strong corrosive acid that is commonly used as a laboratory reagent. It is formed by dissolving hydrogen chloride in water. Gastric acid is the hydrochloric acid component of gastric juice. Caustic Ingestion (Cleaning Products) ( HCl HCL Hairy cell leukemia (HCL) is a rare, chronic, B-cell leukemia characterized by the accumulation of small mature B lymphocytes that have “hair-like projections” visible on microscopy. The abnormal cells accumulate in the peripheral blood, bone marrow (causing fibrosis), and red pulp of the spleen, leading to cytopenias. Hairy Cell Leukemia) from the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy

Endocrine pancreas

Endocrine secretions refer to hormone secretions directly into the bloodstream. The endocrine pancreatic tissue is arranged in circular pancreatic islets, or islets of Langerhans:

  • Functional units of the endocrine pancreas
  • Well-vascularized circular groups of cells 
  • Interspersed throughout the pancreas, in between acini
  • Make up approximately 10%–20% of the organ’s tissue
  • 3 different cell types each produce a different hormone: 
    • Alpha cells → secrete glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions, which ↑ blood glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance levels by:
      • Stimulating glycogenolysis Glycogenolysis The release of glucose from glycogen by glycogen phosphorylase (phosphorolysis). The released glucose-1-phosphate is then converted to glucose-6-phosphate by phosphoglucomutase before entering glycolysis. Glycogenolysis is stimulated by glucagon or epinephrine via the activation of phosphorylase kinase. Glycogen Metabolism and gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis
      • Inhibiting glycolysis Glycolysis Glycolysis is a central metabolic pathway responsible for the breakdown of glucose and plays a vital role in generating free energy for the cell and metabolites for further oxidative degradation. Glucose primarily becomes available in the blood as a result of glycogen breakdown or from its synthesis from noncarbohydrate precursors (gluconeogenesis) and is imported into cells by specific transport proteins. Glycolysis and glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)
    • Beta cells → secrete insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin, which ↓ blood glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance by stimulating:
      • Peripheral glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance uptake
      • Glycolysis Glycolysis Glycolysis is a central metabolic pathway responsible for the breakdown of glucose and plays a vital role in generating free energy for the cell and metabolites for further oxidative degradation. Glucose primarily becomes available in the blood as a result of glycogen breakdown or from its synthesis from noncarbohydrate precursors (gluconeogenesis) and is imported into cells by specific transport proteins. Glycolysis and glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)
    • Delta cells → secrete somatostatin Somatostatin A 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal. Gastrointestinal Secretions, which inhibits:
      • Secretion Secretion Coagulation Studies of multiple hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types, including insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin, glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions, gastrin Gastrin A family of gastrointestinal peptide hormones that excite the secretion of gastric juice. They may also occur in the central nervous system where they are presumed to be neurotransmitters. Gastrointestinal Secretions, cholecystokinin Cholecystokinin A peptide, of about 33 amino acids, secreted by the upper intestinal mucosa and also found in the central nervous system. It causes gallbladder contraction, release of pancreatic exocrine (or digestive) enzymes, and affects other gastrointestinal functions. Cholecystokinin may be the mediator of satiety. Gastrointestinal Secretions, growth hormone, thyroid-stimulating hormone Thyroid-stimulating hormone A glycoprotein hormone secreted by the adenohypophysis. Thyrotropin stimulates thyroid gland by increasing the iodide transport, synthesis and release of thyroid hormones (thyroxine and triiodothyronine). Thyroid Hormones (TSH), and prolactin Prolactin A lactogenic hormone secreted by the adenohypophysis. It is a polypeptide of approximately 23 kd. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Breasts: Anatomy 
      • Gastric acid Gastric acid Hydrochloric acid present in gastric juice. Gastroesophageal Reflux Disease (GERD) secretion Secretion Coagulation Studies
      • Bile Bile An emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum. Gallbladder and Biliary Tract: Anatomy secretion Secretion Coagulation Studies

Neurovasculature

Arterial blood supply

  • Head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess supplied by the pancreatic arcade, which consists of:
    • Anterior and posterior superior pancreaticoduodenal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology:
      • Branch off the gastroduodenal artery (a branch off the hepatic artery Hepatic artery A branch of the celiac artery that distributes to the stomach, pancreas, duodenum, liver, gallbladder, and greater omentum. Liver: Anatomy, which is off the celiac trunk)
      • Anastomoses with the inferior pancreaticoduodenal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
    • Inferior pancreaticoduodenal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
      • A branch off the SMA
      • Splits into anterior and posterior divisions (which anastomose with the superior pancreaticoduodenal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology)
  • Body and tail: 
    • Pancreatic branches of the splenic artery
    • Inferior pancreatic artery: runs along the body and tail
  • Anastomotic branch: connects the pancreaticoduodenal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology to the inferior pancreatic artery
Arterial supply of the pancreas

Arterial supply of the pancreas

Image by Lecturio.

Vascular drainage

Venous drainage is through pancreatic veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology. These veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology drain into the:

  • Pancreaticoduodenal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology → superior mesenteric vein (from the head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess)
  • Splenic vein (from the body and tail)

Lymphatic drainage

Innervation

The pancreas is innervated primarily by the autonomic nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. Nervous System: Anatomy, Structure, and Classification, though pancreatic secretions Pancreatic Secretions Gastrointestinal Secretions are predominantly regulated by other hormone products and chemical signals (e.g., glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance levels, secretin Secretin A peptide hormone of about 27 amino acids from the duodenal mucosa that activates pancreatic secretion and lowers the blood sugar level. Gastrointestinal Secretions, cholecystokinin Cholecystokinin A peptide, of about 33 amino acids, secreted by the upper intestinal mucosa and also found in the central nervous system. It causes gallbladder contraction, release of pancreatic exocrine (or digestive) enzymes, and affects other gastrointestinal functions. Cholecystokinin may be the mediator of satiety. Gastrointestinal Secretions).

  • Sympathetic: T6–T12 thoracic splanchnic nerves and the celiac plexus
  • Parasympathetic: vagus nerve Vagus nerve The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx). Pharynx: Anatomy

Clinical Relevance

  • Acute pancreatitis Pancreatitis Inflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis. Acute Pancreatitis: acute inflammatory process that can be mild or a life-threatening condition. Acute pancreatitis Pancreatitis Inflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis. Acute Pancreatitis occurs when the digestive enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes are activated before they are released into the small intestine Small intestine The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy, causing inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation. Most individuals present with an acute onset of persistent, severe epigastric abdominal pain Abdominal Pain Acute Abdomen radiating to the upper back. The most common causes are gallstones Gallstones Cholelithiasis (gallstones) is the presence of stones in the gallbladder. Most gallstones are cholesterol stones, while the rest are composed of bilirubin (pigment stones) and other mixed components. Patients are commonly asymptomatic but may present with biliary colic (intermittent pain in the right upper quadrant). Cholelithiasis and alcohol abuse. 
  • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus: diseases of abnormal carbohydrate metabolism that are characterized by hyperglycemia Hyperglycemia Abnormally high blood glucose level. Diabetes Mellitus. Type 2 Type 2 Spinal Muscular Atrophy diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus is by far the most common type of diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus in adults, and it presents with peripheral insulin resistance Insulin resistance Diminished effectiveness of insulin in lowering blood sugar levels: requiring the use of 200 units or more of insulin per day to prevent hyperglycemia or ketosis. Diabetes Mellitus and progressive loss of insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin secretion Secretion Coagulation Studies from beta islet cells. Type 1 Type 1 Spinal Muscular Atrophy diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus is characterized by autoimmune destruction of the pancreatic beta cells, leading to absolute insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin deficiency.
  • Glucagonoma Glucagonoma A glucagonoma is a glucagon-secreting neuroendocrine tumor that originates from the β-cells in the pancreatic islets. Most glucagonomas are malignant, and many of them are part of the autosomal dominant condition known as multiple endocrine neoplasia syndrome type 1 (MEN 1). Elevated levels of glucagon lead to increased gluconeogenesis and glycogenolysis. Glucagonoma: glucagon-secreting neuroendocrine tumor Tumor Inflammation, originating from the α cells in the pancreatic islets. Most glucagonomas are malignant, and many are part of the autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance condition MEN1 MEN1 A form of multiple endocrine neoplasia that is characterized by the combined occurrence of tumors in the parathyroid glands, the pituitary gland, and the pancreatic islets. The resulting clinical signs include hyperparathyroidism; hypercalcemia; hyperprolactinemia; cushing disease; gastrinoma; and zollinger-ellison syndrome. This disease is due to loss-of-function of the men1 gene, a tumor suppressor gene on chromosome 11 (locus: 11q13). Multiple Endocrine Neoplasia. Presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor is often with diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus, a characteristic rash Rash Rocky Mountain Spotted Fever called necrolytic migratory erythema Erythema Redness of the skin produced by congestion of the capillaries. This condition may result from a variety of disease processes. Chalazion ( NME NME Recurrent cutaneous manifestation of glucagonoma characterized by necrolytic polycyclic migratory lesions with scaling borders. It is associated with elevated secretion of glucagon by the tumor. Other conditions with elevated serum glucagon levels such as hepatic cirrhosis may also result in similar skin lesions, which are referred to as pseudoglucagonoma syndrome. Glucagonoma), weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types, deep-vein thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus, and neuropsychiatric symptoms.
  • Insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs): insulin-secreting neuroendocrine tumor Tumor Inflammation originating from the β cells of the pancreatic islets. Insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) more commonly presents as a solitary benign Benign Fibroadenoma tumor Tumor Inflammation, but can sometimes be associated with MEN1 MEN1 A form of multiple endocrine neoplasia that is characterized by the combined occurrence of tumors in the parathyroid glands, the pituitary gland, and the pancreatic islets. The resulting clinical signs include hyperparathyroidism; hypercalcemia; hyperprolactinemia; cushing disease; gastrinoma; and zollinger-ellison syndrome. This disease is due to loss-of-function of the men1 gene, a tumor suppressor gene on chromosome 11 (locus: 11q13). Multiple Endocrine Neoplasia. Presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor is with fasting hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, which may manifest as episodes of diaphoresis, palpitations Palpitations Ebstein’s Anomaly, tremor Tremor Cyclical movement of a body part that can represent either a physiologic process or a manifestation of disease. Intention or action tremor, a common manifestation of cerebellar diseases, is aggravated by movement. In contrast, resting tremor is maximal when there is no attempt at voluntary movement, and occurs as a relatively frequent manifestation of parkinson disease. Myotonic Dystrophies, and confusion. 
  • Exocrine pancreatic insufficiency Exocrine pancreatic insufficiency A malabsorption condition resulting from greater than 10% reduction in the secretion of pancreatic digestive enzymes (lipase; proteases; and amylase) by the exocrine pancreas into the duodenum. This condition is often associated with cystic fibrosis and with chronic pancreatitis. Malabsorption and Maldigestion: complication of pancreatic disease in which the pancreas does not secrete sufficient pancreatic juices for digestion Digestion Digestion refers to the process of the mechanical and chemical breakdown of food into smaller particles, which can then be absorbed and utilized by the body. Digestion and Absorption, resulting in maldigestion Maldigestion Malabsorption involves many disorders in which there is an inability of the gut to absorb nutrients from dietary intake, potentially including water and/or electrolytes. A closely related term, maldigestion is the inability to break down large molecules of food into their smaller constituents. Malabsorption and maldigestion can affect macronutrients (fats, proteins, and carbohydrates), micronutrients (vitamins and minerals), or both. Malabsorption and Maldigestion of fat and protein, weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, bloating Bloating Constipation, flatulence, and steatorrhea Steatorrhea A condition that is characterized by chronic fatty diarrhea, a result of abnormal digestion and/or intestinal absorption of fats. Diarrhea (loose, greasy stools). Exocrine pancreatic insufficiency Exocrine pancreatic insufficiency A malabsorption condition resulting from greater than 10% reduction in the secretion of pancreatic digestive enzymes (lipase; proteases; and amylase) by the exocrine pancreas into the duodenum. This condition is often associated with cystic fibrosis and with chronic pancreatitis. Malabsorption and Maldigestion can be caused by chronic pancreatitis Pancreatitis Inflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis. Acute Pancreatitis, cystic Cystic Fibrocystic Change fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, pancreatic duct obstruction, or loss of secretin Secretin A peptide hormone of about 27 amino acids from the duodenal mucosa that activates pancreatic secretion and lowers the blood sugar level. Gastrointestinal Secretions due to surgical resection of stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy and/or bowel.
  • Exocrine pancreatic cancer Exocrine Pancreatic Cancer Pancreatic cancer, consisting mostly of invasive pancreatic ductal adenocarcinoma (PDAC), arises from the ductal cells of the exocrine pancreas and is the 4th leading cause of cancer-related deaths in the United States. Pancreatic cancer has the highest mortality rate among the major cancers, with a 5-year survival rate of only 8%-10%. Exocrine Pancreatic Cancer: highly lethal malignancy Malignancy Hemothorax consisting mostly of invasive pancreatic ductal adenocarcinoma Invasive pancreatic ductal adenocarcinoma Exocrine Pancreatic Cancer ( PDAC PDAC Exocrine Pancreatic Cancer) that arises from the ductal cells Ductal cells Gastrointestinal Secretions of the exocrine pancreas. Risk factors include tobacco smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity, diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus, age, and race. Clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor may include abdominal pain Abdominal Pain Acute Abdomen, jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice, anorexia Anorexia The lack or loss of appetite accompanied by an aversion to food and the inability to eat. It is the defining characteristic of the disorder anorexia nervosa. Anorexia Nervosa, asthenia, weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, Courvoisier sign Courvoisier sign Exocrine Pancreatic Cancer (enlarged but nontender gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract: Anatomy due to common bile Bile An emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum. Gallbladder and Biliary Tract: Anatomy duct obstruction), splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly, and GI hemorrhage.

References

  1. Le T, Bhushan V, Sochat M, et al. (Eds.) (2021). First aid for the USMLE step 1, 31st ed. p. 370. McGraw-Hill Education.
  2. Fernandez-del Castillo C. (2021). Clinical manifestations, diagnosis, and staging of exocrine pancreatic cancer. UpToDate. Retrieved August 17, 2021, from https://www.uptodate.com/contents/clinical-manifestations-diagnosis-and-staging-of-exocrine-pancreatic-cancer
  3. Drake RL, Vogl AW, Mitchell AWM. (2020). Gray’s Anatomy for Students, 4th ed. Churchill Livingstone/Elsevier. 
  4. Talathi S, Zimmerman R. (2021). Anatomy, abdomen and pelvis, pancreas. StatPearls. Retrieved Aug 19, 2021, from https://www.statpearls.com/articlelibrary/viewarticle/26567/ 
  5. Saladin KS, Miller L. (2004). Anatomy and physiology, 3rd ed., pp. 962–964. McGraw-Hill Education.

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