Pancreas
PANCREAS
Study notes covering the definition, functions, location, size and shape, parts, peritoneal relations, relations of the head, neck, body and tail, pancreatic ducts, arterial supply, venous drainage, lymphatic drainage and nerve supply of the pancreas.
Definition
The pancreas (pan = all; kreas = flesh) is a gland that is:
- Partly exocrine
- Partly endocrine
- Exocrine part → secretes digestive pancreatic juice.
- Endocrine part → secretes hormones, e.g. insulin.
It is a soft, lobulated and elongated organ.
Functions of Pancreas
1. Exocrine Function
Exocrine pancreas secretes alkali pancreatic juice containing chemicals.
a. Bicarbonates
Neutralize the acidic content of stomach that enters the small intestine.
b. Pancreatic Enzymes
Digest food material.
- Proteases → trypsin, chymotrypsin → digest proteins.
- Amylases → hydrolyze carbohydrates.
- Lipases → break lipids.
2. Endocrine Function
Islets of Langerhans secrete:
- Insulin
- Glucagon
- Somatostatin
- Pancreatic peptides
Location
- The pancreas lies more or less transversely across the posterior abdominal wall.
- It is at the level of L1 and L2 vertebrae.
- The source flowchart also gives its vertebral level as T12–L3.
- It occupies the epigastric, umbilical and left hypochondriac regions.
Size and Shape
Shape → J-shaped or retort-shaped, set obliquely.
The bowl of the retort represents:
- Head
The stem of the retort represents:
- Neck
- Body
- Tail
Dimensions
Length
12–15 cm
Width
3–4 cm
Thickness
1.5–2 cm
Weight
80–90 g
Volume
70–80 cm³
Consistency
Soft to firm.
Colour
Creamy-pink.
Parts of Pancreas
The pancreas is divided into 4 parts, from right to left:
1. Head
- Enlarged part.
- Lies in the concavity of the duodenum.
2. Neck
Slightly constricted part.
3. Body
Elongated.
4. Tail
- Narrow, pointed part.
- Reaches the hilus of spleen.
Peritoneal Relations of Pancreas
- The ventral surface of pancreas is covered by parietal peritoneum.
- It is crossed by the root of transverse mesocolon.
- The tail of pancreas is its only intraperitoneal part.
- The tail lies in the lienorenal ligament.
- The pancreas lies posterior to the lesser sac.
Head of Pancreas
The head is the enlarged, flattened right end of pancreas.
It is situated within the C-shaped curve of the duodenum.
External Features
The head has:
Three Borders
- Superior
- Inferior
- Right-lateral
Two Surfaces
- Anterior
- Posterior
One Process
Uncinate process.
Uncinate Process
- A hook-like projection at the lower end and left part of the head.
- Projects towards the left.
- It is triangular and hook-like.
- Anteriorly → superior mesenteric vessels.
- Posteriorly → abdominal aorta.
Relations of Head of Pancreas
Three Borders
1. Superior Border
Related to:
- 1st part of duodenum
- Superior pancreaticoduodenal artery
2. Inferior Border
Related to:
- 3rd part of duodenum
- Inferior pancreaticoduodenal artery
3. Right-Lateral Border
Related to:
- 2nd part of duodenum
- Terminal part of bile duct
- Anastomosis between the two pancreaticoduodenal arteries
Two Surfaces
Anterior Surface
Related, from above downwards, to:
- 1st part of duodenum
- Transverse colon
- Jejunum, separated from it by peritoneum
- Transverse mesocolon
Posterior Surface
Related to:
- Bile duct
- Inferior vena cava
- Renal veins / terminal parts of renal veins
- Right crus of diaphragm
Neck of Pancreas
The neck is the slightly constricted part of pancreas between its head and body.
It is directed:
- Forwards
- Upwards
- To the left
External Features
Two Surfaces
- Anterior
- Posterior
Two Borders
- Upper
- Lower
Relations of Neck
Anterior Surface
Related to:
- Peritoneum covering the posterior wall of lesser sac
- Pylorus
Posterior Surface
Related to:
- Termination of superior mesenteric vein
- Beginning of portal vein
Borders
Upper Border
1st part of duodenum.
Lower Border
Root of transverse mesocolon.
Body of Pancreas
- The body is elongated.
- Extends from the neck to the tail.
- Passes towards the left with a slight upward and backward inclination.
External Features — Recent Concept
- Body is slightly triangular in cross-section.
- Two surfaces:
- Anterior
- Posterior
- Two borders:
- Superior
- Inferior
- One process: Tuber omentale
- Rounded, conical elevation from the right end of the superior border.
External Features — Previous Concept
- Body has three surfaces:
- Anterior
- Inferior
- Posterior
- Body has three borders:
- Superior
- Inferior
- Anterior
Relations of Body
Superior Border
Related to:
- Coeliac trunk over the tuber omentale
- Hepatic artery to the right of tuber omentale
- Splenic artery to the left of tuber omentale
Inferior Border
Related to the superior mesenteric vessels at its right end.
Anterior Surface
- Covered by peritoneum.
- Provides attachment to the transverse mesocolon.
Relations Above Attachment of Transverse Mesocolon
1. Lesser Sac
2. Stomach
Relations Below Attachment of Transverse Mesocolon
1. Infracolic Compartment of Greater Sac
2. Coils of Jejunum
3. Duodenojejunal Flexure
4. Left Colic Flexure
Previous Concept
- The anterior surface is divided into:
- Anterior surface
- Inferior surface
- This is done by the anterior border, which provides attachment to the transverse mesocolon.
Posterior Surface
- Devoid of peritoneum.
- Lies on the fusion fascia of Toldt.
- Related to:
- Aorta
- Origin of superior mesenteric artery
- Left suprarenal gland
- Upper pole of left kidney
- Left renal vein / left renal vessels
- Splenic vein → may be embedded in the gland
- Left crus of diaphragm
Tail of Pancreas
- The tail is the narrowest and most left lateral portion of the pancreas.
- It is about 1.5–3.5 cm long.
- It lies in the splenorenal (lienorenal) ligament along with the splenic vessels.
- It is the only mobile part of pancreas.
- It contains the most significant number of islets of Langerhans.
Ducts of Pancreas
The exocrine pancreas is drained by two ducts:
1. Main Pancreatic Duct
Duct of Wirsung
2. Accessory Pancreatic Duct
Duct of Santorini
1. Main Pancreatic Duct — Duct of Wirsung
- About 3 mm in diameter.
- Lies near the posterior surface of pancreas.
- Easily recognized by its white colour.
- Begins at the tail.
- Runs towards the right through the body.
- Bends at the neck.
- Then runs:
- Downwards
- Backwards
- To the right in the head
Herringbone Pattern
- Receives many small tributaries.
- These join it at acute angles to its long axis.
- This produces a “V” shaped pattern.
- This is described as a herringbone pattern.
Relation with Bile Duct
- Within the head of pancreas, the pancreatic duct is related to the bile duct, which lies on its right.
- The two ducts enter the wall of the 2nd part of duodenum.
- They join to form the hepatopancreatic ampulla of Vater.
- It opens by a narrow mouth on the summit of the major duodenal papilla.
- This is 8–10 cm distal to the pylorus.
2. Accessory Pancreatic Duct — Duct of Santorini
- Begins in the lower part of the head.
- Crosses the front of the main duct.
- Communicates with the main duct.
- Opens into the duodenum at the minor duodenal papilla.
- The papilla of the accessory pancreatic duct is situated 6–8 cm distal to the pylorus.
Arterial Supply
The pancreas is supplied by pancreatic branches of:
1. Splenic Artery
Branch of coeliac trunk.
2. Superior Pancreaticoduodenal Artery
Branch of gastroduodenal artery.
3. Inferior Pancreaticoduodenal Artery
Branch of superior mesenteric artery.
Venous Drainage
Venous blood from the pancreas drains into:
1. Portal Vein
2. Superior Mesenteric Vein
3. Splenic Vein
Venous Drainage Diagram Also Shows
- Superior pancreaticoduodenal vein
- Inferior pancreaticoduodenal vein
- Inferior mesenteric vein
- Splenic vein
- Superior mesenteric vein
- Portal vein
Lymphatic Drainage
Lymphatics from the pancreas drain into:
1. Pancreaticosplenic Nodes
Main lymphatic nodes.
2. Coeliac Nodes
3. Superior Mesenteric Nodes
4. Pyloric Nodes
Nerve Supply
The pancreas is supplied by:
1. Parasympathetic Fibres
- From the vagus nerve.
- These are secretomotor fibres.
- They enhance pancreatic secretions along with cholecystokinin produced by the duodenum.
2. Sympathetic Fibres
From:
- Coeliac plexus
- Superior mesenteric plexuses
These are vasomotor.