The pancreas is a soft, delicately lobulated, elongated exo-endocrine gland. The exocrine part secretes the pancreatic juice and the endocrine part secretes the hormones, viz., insulin, etc. The pancreas (in Greek pan: all 1 kreas: flesh) is presumably so termed due to its fleshy look.
The pancreatic juice helps in the digestion of lipids, carbohydrates, and proteins, on the other hand the pancreatic hormones keep glucose homeostasis.
Size And Shape
- The pancreas is “J” shaped or retort shaped being set obliquely. The bowl of retort represents its head and the stalk of retort represents its neck, body, and tail. Its measurements are:
- Length: 12-15 cm
- Width: 3-4 cm
- Thickness: 1.5-2 cm
- Weight: 80-90 grams
The pancreas is located more or less horizontally on the posterior abdominal wall in the epigastric and left hypochondriac regions. It crosses the posterior abdominal wall obliquely from concavity of the duodenum to the hilum of spleen opposite the level of T12-L3 vertebrae.
The greater part of the gland is retroperitoneal behind the serous floor of the lesser sac. Its left extremity- the tail, is located in the lienorenal ligament.
Parts (Subdivisions) and Relationships
For illustrative purposes, the pancreas is subdivided into 4 parts:
- Head (with 1 process- uncinate process).
- Body (with 1 process- tuber omentale).
Head of The Pancreas
The pancreas is deeply situated in the upper part of the abdomen, and concealed by many organs, for this reason not reachable for physical examination.
It’s the enlarged, disk -shaped right end of the pancreas, which is located in the concavity of the C-shaped duodenal loop in front of the L2 vertebra.
The head presents the following external features:
- 3 edges: Superior, inferior, and right lateral.
- 2 surfaces: Anterior and posterior.
- 1 process: Uncinate process. (It’s a hook like process from the lower and left part of the head. It goes toward the left behind the superior mesenteric vessels.).
Superior border is related to:
- first part of the duodenum, and.
- superior pancreatic duodenal artery.
Inferior border is related to:
- third part of the duodenum, and.
- inferior pancreatic duodenal artery.
Right Lateral border is related to:
- 2nd part of the duodenum, and.
- anterior and posterior pancreatic duodenal arterial arcades.
Anterior surface is associated from above downward to:
- gastroduodenal artery,.
- transverse colon,.
- root of the transverse mesocolon, and.
Posterior surface is related to:
- left renal vein,.
- bile duct (being located in a groove, and might be seen embedded in the pancreatic tissue), and.
- right crus of diaphragm.
Uncinate process is related to:
- Anteriorly to superior mesenteric vessels, and.
- Posteriorly to the abdominal aorta.
Close relationship of the bile duct to the head of pancreas clarifies the incidence of jaundice from biliary retention in pancreatitis or tumor of the head of pancreas.
In half of the cases, the gallbladder is distended with bile, and palpable on physical examination.
Neck of The Pancreas
It’s a somewhat constricted part of the gland which connects the head together with the body. It’s about 2.5 cm (1 inch) long andis directed forwards, upward, and to the left.
It presents the following external features:
- 2 surfaces: Anterior and posterior.
- 2 edges: Upper and lower.
- Anterior surface is related to pylorus.
- Posterior surface is related to commencement of the portal vein.
- Upper border is related to the initial part of the duodenum.
- Lower border is related to the root of the transverse mesocolon.
Body of The Pancreas
- It’s the elongated part of the gland going from its neck to the tail.
- It enters toward the left of midline with a small upward and backward inclination.
- It is located in front of the vertebral column at or just below the transpyloric plane.
It’s somewhat triangular in cross section and gifts:
- 3 edges: Anterior, superior, and inferior.
- 3 surfaces: Anterior, posterior, and inferior.
- 1 process: Tuber omentale (a part of the body projects above the smaller curvature of the stomach and comes in touch together with the lesser omentum across the lesser sac).
Anterior border provides the connection to the root of transverse mesocolon.
Superior border is related to the coeliac artery above the tuber omentale, hepatic artery to the right, and splenic artery to the left of tuber omentale.
Inferior border is related to superior mesenteric vessels (at its right end).
Anterior surface (concave and directed forward and upward) is related to:
- lesser sac, and.
Posterior surface (devoid of peritoneum) is related to:
- aorta and origin of the superior mesenteric artery,.
- left kidney and left suprarenal glands, and.
- splenic vein generally is located in a groove below the level of splenic artery.
Inferior surface (covered by peritoneum) is related to:
- duodenojejunal flexure, coils of jejunum, and.
- left colic flexure.
Tail of The Pancreas
- It’s the narrow left extremity of the pancreas.
- It is located in the lienorenal ligament alongside splenic vessels.
- It’s mobile unlike the other major retroperitoneal parts of the gland.
- It includes the largest number of islets of Langerhans per unit of tissue as compared to different parts of the gland.
All these are associated with the visceral surface of spleen between gastric feeling and colic opinion.
Ducts of The Pancreas
Normally there are 2 ducts: chief and accessory, which drain the exocrine secretion into the duodenum.
Primary Pancreatic Duct (of Wirsung)
- It starts in the tail and traverses the entire length of the gland near its posterior surface.
- At the neck, it turns downward, and after that to the right to goes into the 2nd part of duodenum.
- It joins the bile duct as it pierces the duodenal wall to create the hepatopancreatic ampulla (of Vater) which opens by a narrow mouth on the peak of major duodenal papilla 8-10 cm distal to the pylorus.
It gets tributaries (smaller ducts) throughout its length, at right angle to its long axis in a “herringbone pattern”.
It’s the only duct in 90% of cases.
Accessory Pancreatic Duct (of Santorini)
A. It starts in the lower part of the head, and after that runs upward and medially, crossing in front of main pancreatic duct.
B. It opens into the 2nd part of the duodenum on the peak of small duodenal papilla about 2-3 cm above the opening of main pancreatic duct (6-8 cm distal to pylorus).
C. In 40% of cases, it interacts with all the primary duct while crossing it.
The pancreas grows from 2 different buds: the ventral pancreatic bud and the dorsal pancreatic bud, therefore it got 2 ducts.
- The smaller ventral pancreatic bud appears in common with hepatic bud for the liver (later the bile duct).
The bigger dorsal pancreatic bud appears more proximally, directly from the duodenum.
Following rotation of the gut, the ventral pancreatic bud (which creates the posterior part of the head and uncinate process) enters together with the bile duct into the position dorsal to the dorsal pancreatic bud (which creates the staying whole part of the gland). Both buds now fuse and their ducts anastomose with every other in this kind of style the duct of ventral pancreas creates the proximal part of the principal pancreatic duct while the duct of dorsal pancreas creates the rest distal part of the pancreatic duct. The proximal part of the dorsal pancreatic duct between the anastomosis and duodenum stays narrow and creates the accessory pancreatic duct. It generally interacts together with the main pancreatic duct.
- Annular pancreas is a developmental anomaly where a ring of pancreatic tissue encircles the next part of the duodenum.
- Accessory pancreatic tissue could be seen in (a) stomach wall, (b) duodenum (most common), (c) small intestine, (d) Meckel’s diverticulum, (e) greater omentum, and (f) hilum of spleen. It appears in the create of yellowish, lobulated nodules, generally single (1-6 millimeters) in diameter; about 1-third of these nodules include islets of Langerhans.
The pancreas is a high vascular structure and provided by these arteries:
- Splenic artery, a branch of coeliac trunk: The splenic artery is the branch of coeliac trunk and it’s the primary source of blood supply to the pancreas. Its branches provide the body and tail of pancreas. 2 branches are called. 1 large branch which originates near the tail and runs toward the neck is known as arteria pancreatica magna. Another comparatively small branch, which runs toward the tip of the tail, is referred to as arteria caudae pancreatica.
- Superior pancreaticoduodenal artery: The superior pancreaticoduodenal arteryis a branch of gastroduodenal artery.
- Inferior pancreaticoduodenal artery: The inferior pancreaticoduodenal arteryis a branch of superior mesenteric artery.
Both the superior and inferior pancreaticoduodenal arteries divide into anterior and posterior branches, which run between the concavity of the duodenum and the head of pancreas. The anastomoses between anterior and posterior branches create anterior and posterior pancreaticoduodenal arterial arcades.
Since the pancreas grows at the junction of the foregut and midgut, it’s furnished by the branches of the artery of foregut (coeliac trunk) and the branches of the artery of midgut (superior mesenteric artery).
The veins of the pancreas drain into (a) portal vein, (b) superior mesenteric vein, and (c) splenic vein.
The lymphatics from the pancreas follow the arteries and drain primarily into these groups of lymph nodes:
- Pancreaticosplenic nodes (primary group).
- Coeliac nodes.
- Superior mesenteric nodes.
- Pyloric nodes.
The sympathetic and parasympathetic nerve fibres reach the gland along its arteries from coeliac and superior mesenteric plexuses.
The sympathetic provide is vasomotor while the parasympathetic provide restrains the pancreatic secretion.
- Carcinoma of the head of pancreas is common. It compresses the bile duct resulting in consistent obstructive jaundice. It might press the portal vein or may include the stomach because of shut area of these structures to the head of pancreas.
- Acute pancreatitis is the extreme inflammation of the pancreas. It takes place because of obstruction of pancreatic duct, ingestion of alcohol, viral infections (mumps), or trauma. It’s serious affliction because activated pancreatic enzymes leak into the substance of pancreas and begins the autodigestion of the gland. Medically, it presents as quite acute pain in the epigastric region radiating to the back, temperature, nausea, and vomiting. The serum amylase, level is increased 4 times.