Pancreas

PANCREAS

• It consists of exocrine & endocrine parts
• It extends from the concavity of duodenum to the hilum of spleen in the posterior abdominal wall.

SITUATION

• It occupies posterior part of epigastrium & left hypochondrium.

SHAPE

• It resembles a retort-shaped flask

PRESENTING  PARTS

• Pancreas presents head, neck, body & tail.

Head :-

• It is contained within the C-shaped curve of duodenum.
• It lies at a lower level opposite L1 & L2 vertebrae.

Parts–

• 2 Surfaces- anterior & posterior
• 4 Borders- upper, lower, right & left
• 1 Process- uncinate process

Anterior  Surface -

• It is separated from the neck by a groove for gastro-duodenal artery
• Upper part is non-peritoneal & lower part is covered with peritoneum.

Relation–

• Transverse colon
• Transverse mesocolon
• Coils of jejunum
• Superior mesenteric vessels

Posterior  Surface –

• It is non-peritoneal.

Relations-

• Right crus of diaphragm
• Right middle supra-renal artery
• Right gonadal artery
• Right coeliac ganglion
• Cisterna chyli
• Bile duct
• Right sympathetic trunk
• Right psoas major
• Azygos vein
• Renal veins
• Inferior vena cava
• Transverse processes of L1 & L2 vertebrae

Upper  Border –

• It is overlapped by first part of duodenum

Right  Border –

• It is overlapped by second part of duodenum

Lower  Border –

• It is overlapped by third part of duodenum

Left  Border –

• It is overlapped by fourth part of duodenum

Uncinate  Process –

• It is a triangular projection directed medially

Relations-

• In front- Superior mesenteric vessels
• Behind- Abdominal aorta

Neck :-

• It runs upwards & to the left.

Parts-

• 2 Surfaces- anterior & posterior
• 2 Borders- upper & lower

Anterior  Surface –

• It is related with pyloric end of stomach

Posterior  Surface –

• It is non-peritoneal

Relations-

• Superior mesenteric vein
• Trunk of portal vein

Upper  Border –

• It is overlapped by first part of duodenum

Lower  Border –

• It gives attachment to the root of transverse mesocolon

Body :-

• It is triangular on cross section
• It extends from the front of aorta to left kidney

Parts-

• 3 Surfaces- anterior, inferior & posterior
• 3 Borders- superior, anterior & inferior

Anterior  Surface –

• It is covered with peritoneum from superior layer of transverse mesocolon.

Relations-

• Posterior surface of stomach separated by lesser sac.

Inferior  Surface –

• It is covered with peritoneum from inferior layer of transverse mesocolon.

Relations-

• Duodeno-jejunal flexure
• Coils of jejunum
• Left colic flexure

Posterior  Surface –

• It is non-peritoneal.

Relations-

• Abdominal aorta
• Origin of superior mesenteric artery
• Left crus of diaphragm
• Left psoas major
• Left sympathetic trunk
• Left supra-renal gland
• Left kidney
• Left renal vessels
• Pelvis of left ureter
• Left supra-renal vein
• Left gonadal vein
• Splenic vein

Superior  Border –

• It presents a conical projection known as tuber omentale

Relations-

• Coeliac artery lies above the tuber
• Hepatic artery runs right side of the tuber
• Splenic artery runs left side of the tuber

Anterior  Border –

• It separates anterior from inferior surfaces
• It gives attachment to root of transverse mesocolon

Inferior  Border –

• It is related with superior mesenteric vessels

Tail –

• It is the most mobile part of the gland
• It lies at a higher level opposite T12 vertebra
• It passes between the layers of lieno-renal ligament & reaches the spleen.

Relations-

• In front- stomach
• Behind- spleen & splenic vessels
• Below- left colic flexure

PANCREATIC  DUCTS

Main  Duct  of  Wirsung :-

It begins in the tail of pancreas by union of smaller ducts

Passes from left to right through the body of pancreas

It receives smaller ducts which open at regular angles resembling Herring bone pattern

In the neck it passes downwards, backwards to the right

Then it pierces postero-medial wall of 2^nd part of duodenum

Within the wall of duodenum it is surrounded by sphincter pancreaticus

Then the main pancreatic duct unites with bile duct to form Ampulla of Vater

Ampulla is surrounded by sphincter of Oddi

Finally, it opens at the summit of major duodenal papilla

Accessory  Duct  of  Santorini :-

It receives secretion from the uncinate process

Passes upwards to the right in front of main duct

it is connected to the main duct by a communicating duct

Finally, it opens into 2^nd part of duodenum on the summit of minor papilla which is 2 cm above the major papilla

ARTERIAL  SUPPLY

Head  &  Neck :-

• They are supplied by ventral & dorsal anastomoses of superior & inferior pancreatico-duodenal arteries.

Body  &  Tail :-

• They are supplied by pancreatic branches of splenic artery.
• Arteria pancreatica magna is the longer pancreatic branch.
• Occasionally, dorsal pancreatic branch from splenic artery supplies posterior surface of pancreas.
• The outflow of blood from islets drains into acinar capillary plexus known as Insular-acinar portal system.
• It suggests endocrine influence of islet cells upon the exocrine portion of pancreas.

VENOUS  DRAINAGE

• They correspond to arteries & drain into superior mesenteric, splenic & portal veins.

LYMPHATIC  DRAINAGE

Head  &  Neck :-

• Lymph channels from head & neck drain into ventral & dorsal groups of pancreatico-duodenal lymph nodes

Body  &  Tail :-

• Lymph channels from body & tail drain into pancreatico-splenic group of lymph nodes
• Efferent vessels from the above nodes terminate into coeliac & superior mesenteric groups of pre-aortic lymph nodes.

NERVE  SUPPLY

Sympathetic  Fibres –

• Derived from coeliac & superior mesenteric plexuses.

Parasympathetic  Fibres –

• Derived from both vagus nerves.

DEVELOPMENT

• Pancreas develops in 2 parts from – dorsal & ventral pancreatic buds.

Dorsal  Bud :-

• It arises as a diverticulum from the dorsal wall of primitive duodenum, cephalic to the hepatic bud.
• It gives rise to the neck, body, tail & upper part of head of the pancreas.

Ventral  Bud :-

• It grows as a bilobed diverticulum from the hepatopancreatic bud on the ventral wall of primitive duodenum at the junction of fore & mid guts.
• When the second part of duodenum undergoes axial rotation ventral pancreatic bud winds round the posterior surface of duodenum.
• Then it appears on the postero-medial aspect where it meets the dorsal bud.
• It gives rise to lower part of head & uncinate process of the pancreas.

Ducts  of  Pancreas :-

• An oblique communication is established between the ducts of dorsal & ventral buds.
• Main pancreatic duct develops from 3 sources –
• From distal part of dorsal duct
• From the oblique communication between the ducts of dorsal & ventral buds
• From proximal part of primitive bile duct
• Accessory pancreatic duct develops from proximal part of dorsal duct.

Islet  Cells :-

• Islet cells of pancreas develop form detached cells of serous acini.

Connective  Tissue :-

• Stroma develops from the mesenchyme of mesoduodenum.

APPLIED  ANATOMY

Annular  Pancreas :-

• Annular type of head of pancreas encircles the 2^nd part of duodenum
• It produces duodenal obstruction

Carcinoma  of  Head  of  Pancreas :-

• The malignant growth may obstruct the bile duct producing jaundice
• It may compress the portal vein producing ascites
• It may constrict the pylorus producing pyloric obstruction

Pseudo-pancreatic  Cyst :-

• It is a cystic retro-peritoneal pancreatic tumour.
• It displaces the stomach & transverse colon.
• It does not move with respiration.