Download 28-duodenum & Pancreas

Duodenum
It is a C- shaped tube about 10 inch (25 cm ) long. It joins the stomach to the jejunum. It
curves around the head of the pancreas. It lies in the epigastric and umbilical regions.
The 1st inch of the first part resembles the stomach in that it is covered on its anterior and
posterior surfaces with peritoneum and has the lesser omentum attached to its upper
border and the greater omentum attached to its lower border. The lesser sac lies behind this
short segment.
The remainder of the duodenum is retroperitoneal, being only covered by peritoneum.
First part of the Duodenum
It is 2 inch ( 5 cm ) long. It begins at the pylorus about 4 fingerbreadth to the right of the
midline. It runs upward and backward on the right side of the 1st lumbar vertebra. So, it lies
on the transpyloric plane.
Relations
Anteriorly: The guadrate lobe of the liver and the gallbladder.
Posteriorly: The lesser sac (1st inch), gastroduodenal artery, blie duct; portal vein and I.V.C
Superiorly: The enterance into the epiploic foramen
Inferiorly : The head of pancreas.
Second part of the Duodenum
It is 3 inch ( 8 cm ) long. It runs vertically downward in front of the hilum of right
kidney on the right side of the 2nd and 3rd lumbar vertebrae.
About halfway down its medial border, the bile duct and the main pancreatic duct
pierces its wall. They unite to form the ampulla that opens on the summit of the
major duodenal papilla.
The accessory pancreatic duct, if present opens into the duodenum a little higher
( 2 cm ) up on the minor duodenal papilla.
Relation of the Second Part:
• Anteriorly: The fundus of the gallbladder; the right lobe of the liver; transverse
colon and coils of the small intestine.
•Posteriorly: The hilum of the right kidney and right ureter.
• Laterally: The ascending colon; right colic flexure and right lobe of the liver.
•Medially: The head of the pancreas; the bile duct and main pancreatic duct.
Third part of the Duodenum
It is 3 inch (8 cm) long. It runs horizontally to the left on the subcostal plane. It passes in
front of the vertebral column. It follows the lower border of the head of the pancreas.
Relations:
Anteriorly:
The root of the mesentery of the small intestine which contains within it the superior
mesenteric vessels and coils of jejunum.
Posteriorly:
The right ureter; right psoas muscle; I.V.C. and aorta.
Superiorly:
The head of pancreas.
Inferiorly:
Coils of jejunum.
Fourth part of the Duodenum
It is 2 inch ( 5 cm) long. It runs upward and to the left to duodenojejunal flexure. The flexure
is held in position by a peritoneal fold, it is called the ligament of Treitz which is attached to
the right crus of the diaphragm.
Relations:
Anteriorly:
The beginning of the root of the mesentery and coils of jejunum.
Posteriorly:
The left margin of the aorta and the medial border of the left psoas muscle.
Duodenal Recesses
They are 4 small pocketlike pouches of
peritoneum close to the duodenojejunal
junction.
They are superior ; inferior ; paraduodenal
( lateral to 4th part) and retroduodenal
recesses ( behind 4th part). The 3rd lies
behind a vascular fold containing inferior
mesenteric vein and the ascending branch of
the left colic artery in its free margin.
Mucous Membrane and Duodenal Papillae
It is thick. In the 1st part, it is smooth. In the remainder of the duodenum is thrown
into circular folds called the plica circulares.
At the site where the bile duct and the main pancreatic duct pierce the medial wall
of the second part is a small, rounded elevation called the major duodenal papilla.
The accessory pancreatic duct, if pressent, opens into the duodenum on a smaller
papilla about 0.75 inch (1.9cm ) above the major duodenal papilla.
Arteries:
The upper half is supplied by the superior pancreaticoduodenal artery; a branch of the
gastroduodenal artery.
The lower half is supplied by the inferior pancreaticoduodenal artery; a branch of the
superior mesenteric artery.
Veins:
The superior pancreaticoduodenal vein drains into the portal vein. The inferior pancreaticoduodenal vein joins the superior mesenteric vein.
Nerve supply:
Sympathetic and parasympathetic ( vagus) nerves are from celiac and superior mesenteric
plexuses.
Lymph drainage:
The lymph vessels follow the arteries and drains upward via pancreaticoduodenal
nodes to the gastroduodenal nodes and then to the celiac nodes.
It drains downward via pancreaticoduodenal nodes to superior mesenteric nodes
around the origin of the superior mesenteric artery.
Clinical Notes
Important duodenal Relations
1- Cases have been reported in which a large gallbladder stone ulcerated through
the gallbladder wall into the duodenum.
2- Operations on the transverse colon and right kidney have resulted in damage to
duodenum.
Duodenal ulcer
The anterolateral wall is the common site for it. That is because the acid chyme of the
stomach is squirted against this wall.
An ulcer of the anterior wall of the 1st inch may perforate into the upper part of the greater
sac above the transverse colon which directs the escaping fluid into the right lateral
paracolic gutter and then to the right iliac fossa.
An ulcer of the posterior wall of the 1st part may perforate the wall and erodes the large
gastroduodenal artery ( a branch of the hepatic artery ) causing a severe hemorrhage.
Pancreas
It is both exocrine and an endocrine gland. The exocrine produces a secretion that contains
enzymes capable of hydrolyzing proteins. The endocrine portion ( pancreatic islets of
Langerhans ) produces the hormone insulin and glucagon which play a key role in
carbohydrate metabolism.
It is elongated structure that lies in the epigastrium and the left upper quadrant. It is soft and
lobulated and divided into a head; neck; body and tail. It is situated on the posterior
abdominal wall behind the peritoneum. It crosses the transpyloric plane.
To draw it, a point 1 lies on the transpyloric plane 1 inch to the right of the median plane
while the point 2 lies little above and lateral to the crossing of the transpyloric plane and the
left midclavicular plane.
The head is disc shaped and lies within the concavity of the duodenum. The lower part of
the head ( the uncinate process ) extends to the left behind the superior mesenteric vessels.
The neck is the constricted portion of the pancreas which connects the head to the body. It
lies in front of the beginning of the portal vein and the origin of the superior mesenteric
artery from the aorta.
The body runs upward and to the left across the midline. It is triangular in cross section.
The tail passes forward in the splenicorenal ( lienorenal ) ligament and comes in contact
with the hilum of the spleen.
N.B. All parts of tha pancreas are covered by peritoneum from its anterior & inferior surfaces
only. So, it is fixed to posterior abdominal wall.
Relations:
Anteriorly:
From the right to the left:
The transvers colon; transverse mesocolon; the lesser sac cavity which separates
it from the stomach and stomach.
Posteriorly:
From the right to the left:
The bile duct; portal and splenic veins; inferior vena cava ; aorta; the origin of the
superior mesenteric artery; the left psoas muscle; left suprarenal gland; left
kidney and the hilum of the spleen.
Pancreatic ducts
The main duct of the pancreas
begins in the tail and runs the
length of the gland then it is curved
downward in the substance of the
head receiving tributaries on the
way.
It opens into the 2nd part of the
duodenum at about its middle with
the bile duct on the major duodenal
papilla. Sometimes it drains
separately into the duodenum.
The accessory duct of the
pancreas, when present, drains the
upper part of the head and then
opens into the duodenum a short
distance above the main duct(2cm)
on the minor duodenal papilla. It
communicates with the main duct.
Arteries:
The splenic; superior and inferior pancreaticoduodenal arteries.
Veins:
The corresponding veins drain into the portal system.
Nerve Supply:
Sympathetic and parasympathetic ( vagus ) nerve fibers supply the area.
Lymph Drainage:
Lymph nodes situated along the arteries that supply the gland. The efferent
vessels drain into the celiac and superior mesenteric lymph nodes.