panc Flashcards
The pancreas is a soft, elongated, flattened gland that is 12 to 20 cm in length.
The adult gland weighs between 70 and 110 g.
The pancreas is coarsely lobulated and covered with fine connective tissue, without a true capsule. It is primarily retroperitoneal, lying approximately at the level of the L1-L2 lumbar vertebrae lying
approximately at the level of the L1-L2 lumbar vertebrae.
head of the pancreas is on the right, lying within the curvature of the duodenum, and the remainder of the pancreas lies obliquely in the posterior abdomen, with the tail extending as far as the gastric surface of the spleen
The anterior surface of the head of the pancreas is adjacent to the pylorus, the first part of the duodenum, and the transverse colon.
The posterior surface abuts the hilum7 and medial border of the right kidney, the inferior vena cava and the right renal vessels, the right gonadal vein, and the right crus of the diaphragm
The uncinate process (lingula) is a prolongation of pancreatic tissue that projects off the lower part of the pancreatic head, extending upward and to the left. The uncinate process lies anterior
to the aorta and inferior vena cava and is covered superiorly by the superior mesenteric vessels that emerge below the neck of
the pancreas.
The neck of the pancreas is a constricted part of the gland, extending from the head of the pancreas toward the left to connect the head with the body of the pancreas. It is 1.5 to 2 cm long and 3 to 4 cm wide.
Posterior to the neck of the pancreas lies the confluence of the portal vein with the superior mesenteric and splenic veins.
Anteriorly it is covered in part by the pylorus
and peritoneum of the lesser sac. The neck extends to the right as far as the anterosuperior pancreaticoduodenal artery from the
gastroduodenal artery
The body of the pancreas runs toward the left side, anterior to the aorta.
It is retroperitoneal and held against the aorta by the
peritoneum of the lesser sac. The anterior surface of the body is covered by peritoneum of the omental bursa, which separates the stomach from the pancreas.
The antrum and body of the stomach and the transverse mesocolon contact the body anteriorly.
Posterior to the body of the pancreas are the aorta, the origin of the superior mesenteric artery, the left crus of the diaphragm, the left kidney, the left adrenal gland, and the splenic vein.
Posterior to the body of the pancreas are the aorta, the origin of the superior mesenteric artery, the left crus of the diaphragm, the left kidney, the left adrenal gland, and the splenic vein.
The tip of the tail is intraperitoneal lying
between layers of the splenorenal ligament. The relationship of the pancreas to important structures in the posterior abdomen is seen
The main pancreatic duct (of Wirsung) begins near the tail of the pancreas. It is formed from anastomosing ductules draining the lobules of the gland. It courses left to right and is enlarged by additional ducts.
Through the tail and body, the duct lies midway
between the superior and inferior margins and slightly posterior.
The main duct turns caudal and posterior on reaching the head of the pancreas. At the level of the major papilla, the duct turns horizontally to join in most cases with the bile duct
The duct of Wirsung and the common bile duct empty into the duodenum obliquely via the major papilla. The ampulla of Vater is the common pancreaticobiliary channel within the papilla where the 2 ducts come together, separated by common adventitia
The proximal portion of the embryonic dorsal pancreatic duct remains patent in about 70% of adults and empties through the accessory papilla
Pancreas divisum. The embryonic dorsal and ventral ducts fail to fuse.
Most of the pancreatic secretion empties through the accessory papilla. Only pancreatic secretions from the uncinate process and part of the head of the pancreas
The length of the common channel (when present)
averages 4.5 mm, with a range of 1 to 12 mm
Three circular muscle bundles, collectively called the sphincter of Oddi, act as sphincters encircling each duct as well as the ampulla of Vater.
two thirds to three quarters of the general population
has a common channel, whereas about one fifth have completely separate openings and just under 10% have an interposed sputum that separates the 2 ducts.
Long common channels or pancreaticobiliary
malunion can predispose to pancreatitis or biliary cancer
Approximately 70% of the general population has a patent accessory duct (of Santorini), which is also known as the minor duct
The accessory duct lies anterior to the bile duct and drains into the minor papilla, which lies proximal to the major papilla, but is also located in the second portion of the duodenum.
Up to 10% of people have an interruption between
the major papilla and the main duct, with drainage into the duodenum occurring via the minor papilla; this variant is called pancreas divisum
The main pancreatic duct is widest at the head of the pancreas, and the duct gradually tapers as it progresses to the tail
Upper limits of normal for the pancreatic duct diameter in the head (5 mm), body (4 mm), and tail (3 mm) are generally accepted
The pancreas has a rich circulation that is derived from branches of the celiac and superior mesenteric arteries.
The head of the pancreas and surrounding duodenum are supplied by 2 pancreaticoduodenal
arterial arcades.
They are formed by the anterior and
posterior superior pancreaticoduodenal arteries from the hepatic branch of the celiac artery that join a second pair of anterior and posterior inferior pancreaticoduodenal arteries branching from the superior mesenteric artery
The course of the splenic artery is posterior to the body and tail and loops above and below the superior margin of the pancreas.
It gives off the dorsal pancreatic artery, which usually joins one of the posterior superior arcades after giving off the inferior pancreatic artery
The caudal pancreatic artery arises from the left gastroepiploic artery or from a splenic branch at the spleen.
It joins with branches of the splenic and great pancreatic arteries and other pancreatic arteries.
It flows into the portal venous system, which is formed by the joining of the superior mesenteric and splenic veins at the confluence behind the neck of the pancreas.
The portal vein lies behind the pancreas and in front of the inferior vena cava.
The common bile duct lies anterior to the portal
vein with the hepatic artery to the left of the common bile duct.
The splenic vein originates at the hilum of the spleen and curves behind the tail of the pancreas and below the splenic artery, to the right along the posterior surface of the pancreas
The pancreatic veins drain the neck, body, and tail of the pancreas and join the splenic vein. The pancreaticoduodenal veins lie close to their corresponding arteries and empty into the splenic or portal veins.
small periacinar and perilobuar capillary
networks that drain into larger ducts alongside pancreatic
blood vessels
The superior lymphatic vessels run along the
upper border of the pancreas closely with the splenic blood vessels, whereas inferior lymphatic vessels run with the inferior pancreatic artery.
Superior and inferior lymphatic vessels draining the left pancreas, including the tail of the pancreas and left half of the body empty into nodes in the splenic hilum.
The visceral efferent innervation of the pancreas is through the vagi and the splanchnic nerves by way of the hepatic and celiac plexuses.
The efferent fibers of the vagi pass through
these plexuses without synapsing and terminate in parasympathetic ganglia found in the interlobular septa of the pancreas.
The visceral efferent innervation of the pancreas is through the vagi and the splanchnic nerves by way of the hepatic and celiac plexuses.
The bodies of the postganglionic sympathetic
neurons are in the great plexuses of the abdomen.
Their postganglionic fibers innervate only blood vessels. The autonomic fibers, both efferent and afferent, are located in proximity to the blood vessels of the pancreas. The vagi also carry some visceral afferent fibers
The basic subunit of the exocrine portion is the acinus,
which is at its base a spherical mass of dark-staining secretory cells called acinar cells
The spherical acinus connects to a goblet-shaped neck that is composed of tubular cells called
duct cells.
The inner lumen of the acinus forms the terminal portion of the secretory duct
The pancreatic ductal system is nonstriated and is lined by columnar epithelium
acinar cells are tall pyramidal or columnar
epithelial cells, with their broad bases on a basal lamina and their apices converging on a central lumen. In the resting state, numerous eosinophilic zymogen granules fill the apical portion of the cell.
The basal portion of the cells contains 1 or 2 centrally
located, spherical nuclei and basophilic cytoplasm.
The most prominent feature of the acinar cell is the dense zymogen granules that are concentrated in the apical pole.
Rough ER occupies about 20% of the cell volume
It takes up most of the basal region of the acinar cells and interdigitates with the zymogen granules in the apical region. This abundance of rough ER allows the acinar cell to synthesize more protein than any
other parenchymal cell in the body.
centroacinar cells, bridge acinar cells with the ductal epithelium.
These centroacinar cells are pale-staining on H&E staining and smaller than the acinar cells.
The collagen fibers and other extracellular matrix proteins are secreted by a less common resident cell type, the pancreatic stellate cell (PSC).
The islets of Langerhans number about 1 million in the human pancreas
There are 5 major cell types in the endocrine pancreas.
Beta cells are the most numerous, constituting about 50% to 80% of the islets. They secrete insulin and amylin.
PP cells, also known as F cells, make up 10% to 35% and secrete pancreatic polypeptide and adrenomedullin.
Alpha cells make up 5% to 20% and secrete glucagon. The remaining 5% consists of delta cells, which secrete
somatostatin, and epsilon cells, which secrete ghrelin.
Other rarer subpopulations of islets make additional hormones such as galanin.
The pancreas arises from posterior foregut endoderm
Two buds form: 1 dorsal and 1 bi-lobed ventral bud.
About a month into gestation, the foregut evaginates into a condensation of overlying mesenchyme to form the first morphologic evidence of the dorsal bud.
About a week later, a ventral bud forms as an outpouching of hepatic diverticulum. The ventral bud has a bilobed origin, of which the left ventral bud gradually regresses.
Both dorsal and ventral buds undergo elongation of a stalk region and branched morphogenesis
At 37 to 42 days into gestation, as the duodenum grows, the ventral pancreas rotates around the duodenum and fuses with the dorsal pancreas
The dorsal pancreas forms the tail, body, and superior portion of the pancreatic head. It also contains the dorsal duct that forms the distal portion of the main pancreatic duct (of Wirsung) and the entire minor accessory duct (of Santorini).
The ventral pancreas forms the uncinate process and the inferior part of the head.