GASTROENTEROLOGY
,THE PANCREAS
ANATOMY and PHYSIOLOGY
INTRODUCTION
• The pancreas is an extended, accessory digestive gland that is found
retroperitoneally, crossing the bodies of the L1 and L2 vertebrae 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.
o The head lies on the inferior vena cava and the renal vein and is
surrounded by the C loop of the duodenum.
o The tail of the pancreas extends up to the splenic hilum.
o 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 AND FUNCTION
• Divisions
o The head of the pancreas is the enlarged part of the gland surrounded by
the C-shaped curve of the duodenum. On its way to the descending part
of the duodenum, the bile duct lies in a groove on the posterosuperior
surface of the head or is embedded in its substance.
o The body of the pancreas continues from the neck and passes over the
aorta and L2 vertebra. The anterior surface of the body of the pancreas is
covered with peritoneum. The posterior surface of the body is devoid of
peritoneum. It is in contact with the aorta, the superior mesenteric artery
(SMA), the left suprarenal gland, the left kidney, and renal vessels.
o The neck of the pancreas is short.
o The tail of the pancreas lies anterior to the left kidney, closely related to
the splenic hilum and the left colic flexure.
o The main pancreatic duct , or duct of Santorini, carrying the pancreatic
secretions joins with the bile duct to form the hepatopancreatic ampulla,
which opens into the descending part of the duodenum.
o The minor pancreatic duct, the Santorini duct
o The hepatopancreatic sphincter of Oddi around the hepatopancreatic
ampulla is a smooth muscle sphincter that controls the flow of bile and
pancreatic juice into the ampulla and inhibits reflux of duodenal
substances into the ampulla.
o The major papilla, the duct in which the biliary tract and the pancreatic
duct come together in the duodenum
CELL TYPES
• Approximately 80% - exocrine pancreatic tissue.
o Pancreatic acini (pyramidal acinar cells with the apex directed towards
the lumen) with acinar cells
§ These contain dense zymogen granules in the apical region,
whereas the basal region contains the nucleus and endoplasmic
reticulum (which aids in synthesizing the digestive enzymes).
, § These enzymes are stored in secretory vesicles called the Golgi
complex.
§ The basolateral membrane of the acinar cells contains several
receptors for neurotransmitters including secretin,
cholecystokinin, and acetylcholine, which regulate exocytosis of
the digestive enzymes.
o Duct cells (5%)
• 20% – endocrine pancreatic tissue
o The islet of Langerhans, which contain the endocrine cells.
§ There are 4 types of endocrine cells (A cells produce glucagon, B
cells produce insulin, D cells produce somatostatin, and F cells
produce pancreatic polypeptide).
o Stellate cells are a direct formation of epithelial structures within the
pancreas. In conditions like chronic pancreatitis, these cells promote
inflammation and fibrosis.
EMBRYOLOGY
• Development
o The pancreas develops from the posterior foregut endoderm. At about 4
weeks gestation, this endoderm first gives rise to dorsal and ventral buds,
which gradually elongate.
o Around week 6, the ventral bud rotates around the then developing
duodenum and eventually fuses with the dorsal bud at about the 17th
week of gestation to form the pancreas.
o The dorsal bud thus forms the upper part of the pancreatic head, the
body, and the tail, whereas the ventral bud forms the lower part of the
pancreas and the uncinate process.
o The ventral duct forms the proximal portion of the major pancreatic duct,
which opens into the duodenum via the ampulla of Vater.
o The dorsal duct forms a part of the major ducts as well as the minor duct
or the accessory duct of Santorini.
§ The latter usually empties through the ampulla of Vater but may
empty independently in approximately 5% of people.
BLOOD SUPPLY AND LYMPHATICS
• Arterial Supply
o Branches
§ Branches of the splenic artery (a branch of the celiac trunk)
§ Superior mesenteric artery (SMA)
§ Common hepatic artery provide blood supply to the pancreas.ì
o Tissue supplied:
§ 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.
,THE PANCREAS
ANATOMY and PHYSIOLOGY
INTRODUCTION
• The pancreas is an extended, accessory digestive gland that is found
retroperitoneally, crossing the bodies of the L1 and L2 vertebrae 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.
o The head lies on the inferior vena cava and the renal vein and is
surrounded by the C loop of the duodenum.
o The tail of the pancreas extends up to the splenic hilum.
o 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 AND FUNCTION
• Divisions
o The head of the pancreas is the enlarged part of the gland surrounded by
the C-shaped curve of the duodenum. On its way to the descending part
of the duodenum, the bile duct lies in a groove on the posterosuperior
surface of the head or is embedded in its substance.
o The body of the pancreas continues from the neck and passes over the
aorta and L2 vertebra. The anterior surface of the body of the pancreas is
covered with peritoneum. The posterior surface of the body is devoid of
peritoneum. It is in contact with the aorta, the superior mesenteric artery
(SMA), the left suprarenal gland, the left kidney, and renal vessels.
o The neck of the pancreas is short.
o The tail of the pancreas lies anterior to the left kidney, closely related to
the splenic hilum and the left colic flexure.
o The main pancreatic duct , or duct of Santorini, carrying the pancreatic
secretions joins with the bile duct to form the hepatopancreatic ampulla,
which opens into the descending part of the duodenum.
o The minor pancreatic duct, the Santorini duct
o The hepatopancreatic sphincter of Oddi around the hepatopancreatic
ampulla is a smooth muscle sphincter that controls the flow of bile and
pancreatic juice into the ampulla and inhibits reflux of duodenal
substances into the ampulla.
o The major papilla, the duct in which the biliary tract and the pancreatic
duct come together in the duodenum
CELL TYPES
• Approximately 80% - exocrine pancreatic tissue.
o Pancreatic acini (pyramidal acinar cells with the apex directed towards
the lumen) with acinar cells
§ These contain dense zymogen granules in the apical region,
whereas the basal region contains the nucleus and endoplasmic
reticulum (which aids in synthesizing the digestive enzymes).
, § These enzymes are stored in secretory vesicles called the Golgi
complex.
§ The basolateral membrane of the acinar cells contains several
receptors for neurotransmitters including secretin,
cholecystokinin, and acetylcholine, which regulate exocytosis of
the digestive enzymes.
o Duct cells (5%)
• 20% – endocrine pancreatic tissue
o The islet of Langerhans, which contain the endocrine cells.
§ There are 4 types of endocrine cells (A cells produce glucagon, B
cells produce insulin, D cells produce somatostatin, and F cells
produce pancreatic polypeptide).
o Stellate cells are a direct formation of epithelial structures within the
pancreas. In conditions like chronic pancreatitis, these cells promote
inflammation and fibrosis.
EMBRYOLOGY
• Development
o The pancreas develops from the posterior foregut endoderm. At about 4
weeks gestation, this endoderm first gives rise to dorsal and ventral buds,
which gradually elongate.
o Around week 6, the ventral bud rotates around the then developing
duodenum and eventually fuses with the dorsal bud at about the 17th
week of gestation to form the pancreas.
o The dorsal bud thus forms the upper part of the pancreatic head, the
body, and the tail, whereas the ventral bud forms the lower part of the
pancreas and the uncinate process.
o The ventral duct forms the proximal portion of the major pancreatic duct,
which opens into the duodenum via the ampulla of Vater.
o The dorsal duct forms a part of the major ducts as well as the minor duct
or the accessory duct of Santorini.
§ The latter usually empties through the ampulla of Vater but may
empty independently in approximately 5% of people.
BLOOD SUPPLY AND LYMPHATICS
• Arterial Supply
o Branches
§ Branches of the splenic artery (a branch of the celiac trunk)
§ Superior mesenteric artery (SMA)
§ Common hepatic artery provide blood supply to the pancreas.ì
o Tissue supplied:
§ 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.
