18 Hepatobiliary System and Peritoneal Cavity

1. it becomes double in certain areas. This double layer of peritoneum is given different names: mesentery, ligament, fold, or omentum.
2. it almost completely surrounds some parts of the intestinal tract. These parts are called intraperitoneal structures.
3. it only covers the anterior part of some structures. These structures are called retroperitoneal. Retroperitoneal structures include: urinary system, ascending colon, descending colon, most of the duodenum, pancreas (except for its tail).
4. it produces a covering around some of the intestines. The covering is called its serous coat.
5. peritoneal folds are usually caused by underlying blood vessels, ducts or embryonic remnants.

The gut and colon which have retained their intact mesentery are afforded varying degrees of mobility depending on the extent of the mesentery. The small intestine, cecum, or sigmoid colon may be found in hernial sacs. The lower free border of the omentum between the liver and the stomach is known as the FORAMEN OF WINSLOW or EPIPLOIC FORAMEN (Netter 269) . Occasionally, abdominal viscera, especially the greater omentum will pass through the foramen to become an epiploic hernia.

The Greater Omentum (Netter 263)

The greater omentum is formed by the dorsal mesentery as it extends from the posterior wall, encompassing the stomach and spleen and then descending into a large loop which will encompass the transverse colon and finally fuse with the posterior wall.

The greater omentum is mobile and will move to a site of inflammation or infection and wall it off from the abdomen, thus preventing the spread of infection.

 Omental Bursa or Lesser Peritoneal Sac (Netter 266)

The omenta together close off a portion of the peritoneal sac which is known as the LESSER SAC or OMENTAL BURSA. The peritoneal sac proper becomes the GREATER SAC. The opening into the lesser sac is through the epiploic foramen (of Winslow).

The omental bursa is equivalent to the embryologic right cavity of the abdomen. The peritoneal sac proper is the adult counterpart to the left embryologic abdominal cavity.

Ligament – a double layer of peritoneum which connects one abdominal organ to another or to the abdominal body wall:

Ligaments associated with the liver:

● Falciform

● Ligamentum teres

● Ligamentum venosum

● Hepato-duodenal ligament

● Coronary ligament

● Right & left triangular ligaments

The falciform ligament (Netter 249) is derived from the ventral mesentery between the ventral wall and the liver. On the lower free border of the falciform ligament is the ligamentum teres.  The ligamentum teres is the obliterated umbilical vein which carried blood from the mother to the fetus.

The peritoneum does not enclose the entire surface of the liver. Rostrally, the liver literally grows into the inferior surface of the diaphragm. In this region, the peritoneum is reflected from the liver onto the inferior surface of the diaphragm. This area on the liver is known as the BARE AREA.

The bare area is bordered by the coronary ligament (the reflected peritoneum). The extreme right and left of the coronary ligament are angular in shape. These are known as the right and left triangular ligaments, respectively.

The umbilical vein was connected to the caval system by the ductus venosus. The obliterated ductus venosus is the ligamentum venosum (Netter 277). The patent ductus venosus in the fetus allows maternal blood to by-pass the fetal liver.

The hepato-duodenal ligament (Netter 278 – top) contains the portal vein (venous drainage from the digestive tract), the common bile duct, and the hepatic artery proper (from the celiac trunk of the aorta). The hepato-duodenal ligament comprises the lower free border of the lesser omentum; i.e., that portion which connects the liver to the duodenum.

Ligaments associated with the stomach: (Netter 266)

● Gastro-phrenic ligament

● Gastro-colic ligament

● Gastro-splenic ligament

The gastro-hepatic ligament, which connects the stomach and liver, forms most of the lesser omentum.

The gastro-phrenic ligament (Netter 266, 268) is derived from the remaining dorsal mesentery which was between the posterior abdominal wall and the stomach. It has moved rostrally on the stomach with the development of the diaphragm.

Moving caudally, the dorsal mesentery becomes the gastro-splenic ligament connecting the stomach to the spleen.

The gastro-colic ligament (Netter 266) is the peritoneum which joins the stomach to the transverse mesocolon. It is part of the greater omentum.

The spleen is also attached to the posterior abdominal wall by peritoneum. This attachment is the lienal-renal ligament (Netter 268).

The phrenico-colic (Netter 266, 268) ligament is the peritoneal connection between the left colic flexure and the diaphragm. The inferior border of the spleen rests on this ligament.

The Ligament of Treitz (Netter 264) is not a peritoneal structure. It lies behind the peritoneum and is a fibro-muscular band which attaches the duodenum to the diaphragm. It is an important landmark as it may be palpated through the peritoneum, and it marks the duodenal-jejunal junction.

Innervation of the Peritoneum

The parietal peritoneum is innervated with somatic sensation by nerves T7 – T12. It is sensitive to pain, touch, and temperature. The visceral peritoneum is not innervated by these somatic nerves and is therefore not sensitive to somatic pain. The visceral peritoneum IS sensitive to visceral pain – stretching and noxious stimuli. These nerves accompany the autonomic nerves which supply the gut itself and can give rise to referred pain on the body surface (see later chapter).

Clinical Note: Peritonitis is inflammation and infection of the peritoneum and commonly results from a burst appendix that leaks feces into the peritoneal cavity, from a penetrating wound to the abdomen, from a perforating ulcer that leaks stomach contents or form poor sterile technique during abdominal surgery. peritonitis can be treated can be treated by rinsing the peritoneum with large amounts of sterile saline and giving antibiotics (peritoneal lavage).

Paracentesis. When a patient with a peritnoeal infection is supine, inflammatory fluid collects in the subphrenic and hepatorenal recesses, as well as the pelvic cavity. Diagnostic steps include percussion along the lateral abdomoinal walls and radiographic examination to determine a fluid level. Treatment includes puncture of the abdominal wall to withdraw fluid. A cannula inserted in the flank will pass through the skin, superficial fascia, deep fascia, aponeurosis of the external oblique muscle, internal oblique muscle, transverse abdominus muscle, transversalis fascia and extraperitoneal fat and the parietal peritoneum, A video demonstrating the technique of paracentesis is shown here (from the New England Journal of Medicine’s series of Videos in Clinical Medicine).

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Paracolic Gutters (Netter 265; 341, 345)

The attachments of the mesenteries and the positions of the abdominal viscera form partially sealed off channels, gutters. These gutters may aid in the spreading of infection in the abdomen or be the sites of fluid collection. The phrenico-colic ligament and the root of the mesentery are effective barriers to the spread of infection.

A potential site for collection of fluid on the right side is the hepatorenal pouch (Pouch of Morrison). This area is bounded medially by the right kidney, antero-superiorly by the liver and drains along the right colic gutter into the pelvis.

A summary of the various names used to describe different parts of the peritoneal reflections: coronary ligament superior border inferior border right triangular ligament – from liver to right kidney left triangular ligament falciform ligament – from anterior abdominal wall to liver ligamentum teres – in free margin of the falciform ligament lesser omentum – extends from liver to lesser curvature of stomach and first part of duodenum hepatogastric part – from liver to lesser curvature of stomach hepatoduodenal part – free margin of lesser omentum from liver to first part of duodenum greater omentum transverse mesocolon – from transverse colon to posterior abdominal wall mesentery of the small intestine – from jejunum and ileum to the root of the mesentery on the posterior wall of the abdominal cavity. The root extends obliquely across the posterior abdominal wall from the beginning of the jejunum to the end of the ileum at the cecum. lienalrenal ligament – double layer of peritoneum extending from the spleen to the anterior surface of the left kidney sigmoid mesocolon – from sigmoid colon to posterior abdominal wall over the psoas muscle mesoappendix – from base of appendix to its apex

ABDOMINAL VISCERA

Read Overview of Abdominal Viscera and Digestive Tract section in Moore, pp 226-227)

The functions of the gastrointestinal system include ingestion, endocrine and exocrine secretion, digestion, absorption, and excretion.

The GI tract can be thought of as a tube within a tube. While we typically think of ingesting foodstuffs, in reality, the gut is continuous with our external environment. Thus, our true inside is the region between the visceral and parietal peritoneum (and the space between the visceral and parietal pleura and visceral and parietal serous pericardium in the thorax).

In discussing the viscera, we categorize the GI system into three regions: foregut, midgut, and hindgut. We will define each of these subsequently, however for location of the individual viscera, reference our prior discussion of abdominal quadrants/regions in the abdominal wall section. As we discuss organs, we will consider their structure, overall function, blood supply, innervation, and lymphatic drainage. In addition, we will discuss the overall blood supply, innervation, and lymphatic drainage presently.

What ensues is a general schematic of the viscera and associated structures, a good way to think of it is as a “flythrough” of what food sees from oral to anal orifices.

Major Blood Supply (Netter 259,260)

It is important to have a concept of the derivation of the major arterio-venous supply of the GI system. Logically, once the aorta gives off the coronary arteries, brachiocephalic trunk, left common carotid and left subclavian branches, the remainder of blood supply to the body must be derived from the thoracic and abdominal aorta (epigastric anastomoses excluded). As the aorta descends, it passes between the crura of the diaphragm at the level of T12 (see posterior abdominal wall section of syllabus). From this point on the aorta gives off many branches, some of which are paired, and some unpaired.

Terminal Branches: The aorta bifurcates at the level of L4. It is important to note that the umbilicus lies at the level of L3, and serves as a useful landmark for abdominal aortic palpation.

After it bifurcates, the aorta becomes the Common Iliac Arteries (2). These then branch into internal and external iliac branches (the external iliac then becomes the femoral artery). The last terminal branch is the Median Sacral Artery (1). It gives rise to the 5^th lumbar arteries.

Unpaired Visceral Branches: These provide the majority of perfusion to the viscera. The first is the Celiac Trunk, which supplies most of the foregut via the Common Hepatic, Splenic, and Left Gastric Arteries. The second is the Superior Mesenteric Artery (SMA), which supplies most of the midgut. The third is the Inferior Mesenteric Artery (IMA), which supplies most of the hindgut.

Paired Visceral Branches: Middle Suprarenal Arteries (2), Renal Arteries(2), Gonadal Arteries (2, testicular/ovarian).

Somatic/Parietal branches: Fortunately these five vessels can be whittled down into two categories. The first four are the 1^st to 4^th Lumbar Arteries (2 each). These arteries correspond to the posterior intercostal arteries. A 5th pair of lumbar arteries arises from the median sacral. The last artery is the Inferior Phrenic Artery (2). This serves the diaphragm in addition to giving off the Superior Suprarenal Arteries.

Venous Drainage: In general, the venous structures have names identical to the arterial ones, with the exceptions of the existence of the Hepatic Portal Vein (Netter 292) accepting drainage from the Superior Mesenteric Vein (SMV) and Inferior Mesenteric Vein (IMV) via the Splenic Vein (more later), the Ascending Lumbar Veins draining the lumbar veins and becoming the Azygos and Hemiazygos Veins, and the ultimate drainage to the Inferior Vena Cava. Lastly, note that there is no Celiac Vein.

 

Innervation: Overview of Viscera (Netter 297, 298, 299, 300, 301, 302)

The major innervation of the viscera is autonomic in nature. Sensory innervation runs along autonomic pathways and is typically limited to detecting stretch related phenomena.

●Sympathetic innervation from esophagus to splenic flexure  (i.e, the foregut and midgut) derives from the Thoracic Splanchnic Nerves (T5-12) and Sympathetic Trunk (Thoracolumbar), which synapse in the Celiac and Superior Mesenteric Plexuses. Parasympathetic innervation from esophagus to splenic flexure derives from the Vagus Nerve.

●The hindgut past the splenic flexure receives sympathetic innervation from the Lumbar Splanchnic Nerves which pass to the Inferior Mesenteric, Superior and Inferior Hypogastric, and Rectal Plexuses. The Parasympathetics come from the Pelvic Splanchnic Nerves (note these are not sympathetic in nature) passing to the Rectal Plexus. Preganglionic parasympathetic fibers of vagal and pelvic splanchnic origin synapse in Meissner’s (submucous) and Auerbach’s (myenteric) plexuses in the gut wall (think: long preganglionic, short postganglionic fibers). The only TTPP (temperature, touch. Pressure, pain) sensation and voluntary efferent fibers exist to serve the anal canal through the Pudendal Nerve (see anal canal for more detail).

Autonomic Nerves of the Abdomen (Moore 301 – 305)

For autonomic innervation of the abdominal viscera, several different splanchnic nerves and one cranial nerve (Vagus  CN X) deliver presynaptic sympathetic and parasympathetic fibers to the abdominal aortic plexus and its associated sympathetic ganglia. Theh peri-arterial extensions of these plexuses deliver post-synaptic fibers and the continuations of parasympathetic fibers to the viscera, where intrinsic parasympathetic ganglia occur.

These ganglia and splanchnic nerves are:

Sympathetic chain ganglia – are composed primarily of ascending and descending preganglionic sympathetic visceral motor fibers and visceral sensory fibers with cell bodies located in the dorsal root ganglia.

Prevertebral ganglia – include the celiac, superior mesenteric, aorticorenal and inferior mesenteric ganglia, usually located near the origin of the respective arteries. They receive preganglionic sympathetic fibers by way of the greater, lesser, least and lumbar splanchnic nerves.

Splanchnic nerves:

♦Contain preganglionic visceral motor fibers with cell bodies located in the intermediolateral cell columns of the spinal cord

♦The greater splanchnic nerve, from (T5 – T9), enters the celiac ganglion, the lesser splanchnic nerve (from T10, T11) enters the superior mesenteric ganglion, the least splanchnic nerve (from T12) enters the aorticorenal ganglion and the lumbar splanchnic nerves (from L1-L2) enter the inferior mesenteric ganglion and superior hypogastric plexus. After synapsing in these ganglia, the postganglionic nerves travel along branches of the associated arteries (celiac, SMA, renal, IMA) to reach their destination. Visceral sensory fibers also travel retrogradely along these sympathetic nerves to enter specific spinal cord levels to give referred pain to these dermatomes:

Foregut – supplied by celiac trunk and greater splanchnic nerve – T5 – T9 – epigastric area

Midgut – supplied by SMA and lesser splanchnic nerve – T10-T11 – periumbilical region

Kidneys – supplied by renal arteries and least splanchnic nerve – T12 – hypogastric area

Hindgut – supplied by IMA and lumbar splanchnic nerves – L1, L2 – inguinal region

 

Lymphatic Overview of Viscera (Netter 261)

The GI system drains to variously named colic nodes and then onto the Inferior Mesenteric and Superior Mesenteric Nodes. These then drain to the Celiac Nodes. The foregut structures generally drain to nodes named after their structure (cystic, pancreaticoduodenal, pancreaticosplenic, aortic, hepatic, etc…) From here they drain directly to the celiac, or through the superior mesenteric nodes to the celiac. You may want to note that the inferior mesenteric, superior mesenteric, and celiac nodes are together called the pre-aortic nodes. The celiac nodes drain to the cisterna chyli, which is the lowest portion of the thoracic duct.

The majority of the Foregut blood supply is derived from the Celiac Trunk.  (Moore table 2.7 pg 236 for an overview of Foregut arterial supply).

 

THE HEPATOBILIARY SYSTEM (Moore 263-288)  

The Spleen (Netter 282, 283, 284,; Moore 263)

The spleen is a triangular organ which lies to the left and posterior to the stomach with the exception that the spleen’s notched anterior border is lateral to the greater curvature of the stomach. The long axis of the spleen is along the 10th rib.

The spleen is covered with peritoneum and supported by the gastro-splenic and lieno-renal (splenorenal) ligaments. The spleen rests on the phrenico-colic ligament although it is not connected to it.

The spleen relates to the kidney, stomach, pancreas, and colon on its medial side. The medial surface of the spleen has smooth fossae where it rests against each organ except for the pancreas which is in contact with the hilus.

The blood supply to the spleen is from the celiac trunk by way of the splenic artery which courses retroperitoneally and reaches the spleen by way of the lienorenal ligament. Venous return is by the splenic vein, a major branch of the portal vein)

Lymphatic drainage occurs along the splenic artery to the celiac nodes.

Clinical Correlation: The normal spleen may frequently be accompanied by accessory spleens (10%). (Moore 281) The accessory spleens are very similar to lymph nodes and are usually asymptomatic. The normal spleen (not enlarged) cannot be palpated below the costal margin as it rests on the phreno-colic ligament. A palpable spleen is likely to be pathologic. Splenomegaly is caused by venous congestion resulting from thrombosis of the splenic vein or portal hypertension which causes sequestering of blood cells, leading to thrombocytopenia (a low platelet count) and easy bruising. It has symptoms of fever, diarrha, bone pain, weight loss and night sweats. Rupture of the spleen occurs frequently by fractured ribs or sever blows to the left hypochondrium and causes profuse bleeding. A ruptured spleen is difficult to repair, consequently, splenectomy is performed to prevent the patient from bleeding t o death. The spleen may be removed surgically with minimal effect on body function because its functions are assumed by other reticuloendothelial organs.

 

The Liver (Netter 277, 278, 279; Moore 268-276)

The liver is the largest internal organ of the body. The superior surface is smooth and rounded where it fits against the overlying diaphragm. It is almost completely surrounded by peritoneum except for a BARE AREA on the superior surface which is in direct contact with the diaphragm. The bare area is surrounded by the coronary ligament, the right and left triangular ligaments. The falciform ligament attaches the liver to the ventral abdominal wall. The inferior anterior border forms an acute angle with the internal anterior border which lies over the gall bladder, stomach, and transverse colon.

The falciform ligament (Netter 277) divides the liver into a right and left half; this serves as an anatomic division of the liver, on the anterior surface, into the right and left lobes. On the posterior surface, the fossae made by the inferior vena cava and the gall bladder serve as a marker for the functional division of the right and left lobes. The caudate and quadrate lobes belong to the left lobe. (Note: Descriptively, but not functionally, the caudate and quadrate lobes are referred to as part of the right lobe of the liver.)

The caudate lobe of the liver is that portion on the posterior surface between the inferior vena cava and the ligamentum venosum. The caudate lobe also lies anterior to the inferior vena cava. The quadrate lobe is that portion of the liver on the posterior surface between the fossa for the gall bladder and the ligamentum teres. The quadrate lobe also lies anterior to the gall bladder. The “functional divisions” of the liver refer to the fact that there is relatively little overlap in the arterial supply and venous drainage between the right and left lobes.

The porta hepatis (Netter 284) is the hilus of the liver. Here, the hepatic arteries and portal vein enter the liver and the bile ducts exit. The porta hepatis is on the visceral surface. The margins of the porta serve as the site of attachment of the lesser omentum to the liver. The peritoneum is reflected back over the liver from here. (Remember there are blood vessels and nerves between the peritoneal layers.)The main arterial blood supply to the liver (Netter 283) is from the right and left hepatic arteries which arise from the hepatic artery proper which is ascending in the hepato-duodenal ligament. The cystic artery, the blood supply to the gall bladder, arises from the right hepatic artery.

The cystic artery is identified as the artery that passes through the triangle of Calot, which is bounded by the cystic duct, the hepatic duct, and the lower edge of the liver.

The portal venous supply, which comes from the gastro-intestinal tract exclusively, reaches the liver by passing through the hepato-duodenal ligament. The portal vein is formed by the superior mesenteric vein and the splenic vein. The portal vein divides into the right and left hepatic portal veins at the porta hepatis. The inferior mesenteric vein (usually) enters the portal vein by way of the splenic vein.

The right and left hepatic veins drain the liver into the inferior vena cava. These two veins are located in the fossa for the inferior vena cava on the posterior surface of the liver.

Clinical Correlation: Cirrhosis of the liver is the result of atrophy of the liver parenchyma and a hypertrophy of the connective tissue. Over time, there will be jaundice and portal hypertension (see below). Jaundice is an accumulation of bile pigment in the blood stream. This is frequently a result of obstruction of the duct system. Bile pigments accumulate in the blood, giving the skin and eyes a characteristic yellow hue, accompanied by itching. The liver is frequently a site for secondary metastasis of cancer from almost any part of the body because of its great vascularity.

Liver Disease and Portal Hypertension (Moore 280; Blue Box p. 288)

Porta-caval communication exists in several places (Netter 292).The consequences of  portal hypertension in these areas are  described below.

1) The interference of portal-systemic communication in the liver causes the increase in portal pressure or portal hypertension.

2) The esophageal branch of the left gastric vein anastomoses with the azygos vein of the thorax. Portal hypertension will cause esophageal varices which are almost always clinically significant. Rupture of these varices is a common cause of death in portal hypertension.

3) The superior hemorrhoidal branch of the inferior mesenteric vein and the hemorrhoid plexus of the hypogastric vein can become dilated and cause “piles” or rectal hemorrhoids.

4) Retroperitoneal veins arising from the pancreatico-duodenal portal drainage and the renal systemic drainage as well as the colic portal veins and the lumbar systemic veins. Either site may become engorged with an increase in portal pressure. Such veins are known as veins of Retzius.

5) Portal veins located in the falciform ligament near the ligamentum teres communicate with the systemic para-umbilical veins on the superficial abdominal wall. Engorgement of these veins results in a condition known as “Caput Medusa“.

Clinical Correlation

Surgical correction of portal hypertension. The life-threatening consequences of portal hypertension are amenable to surgical correction to provide routes for visceral blood to bypass the obstructed liver. Surgical creation of a portacaval fistula produces a side-to-side anastamosis between the hepatic portal vein and the inferior vena cava, across the epiploic foramen. A splenorenal anastamosisis also a common procedure. SPlenectomy is followed by anastamosis of the splenic vein to the left renal vein. ALthough shunts reduce the pressure-related dangers inherent in varices, toxic blood shunted around the obstructed liver has a ong-term effect on the central nervous system. Thus encephalopathy results from alcohol-related liver disease.

Gall Bladder (Netter 280, 281; Moore 278)

The gall bladder is a pear-shaped organ which lies in a fossa on the visceral surface of the liver. The gall bladder develops as an out-pouching of the hepatic diverticulum. The distal part becomes the gall bladder and the proximal part the cystic duct. The gall bladder is divided into three parts: the fundus, the body, and the neck. The fundus usually lies inferior to the inferior border of the liver at the junction of the 9th rib and the linea semilunaris. The cystic duct is somewhat like a series of pouches which are separated by cystic folds. The first pouch of the cystic duct, “Hartman’s pouch”, may be a site for gall bladder stones to lodge. The function of the folds within the cystic duct is to act as a valve-like mechanism to prevent the spontaneous release of bile from the gall bladder. The name of this valve is “the Spiral valve of Heister”, The cystic duct joins the hepatic duct at an acute angle to form the common bile duct. The common bile duct joins the pancreatic duct just before entering the duodenum. The blood supply to the gall bladder is the cystic artery which arises from the right hepatic artery and crosses the cystic-hepatic triangle or the Triangle of Calot (Netter 280; 283b) The lymphatic drainage of both the liver and the gall bladder is to nodes in the lesser omentum (3-6 in number). Two of these nodes are constant: the node of the cystic angle and the node of the foramen of Winslow. Parasympathetic innervation is from the vagus nerve vi the celiac plexus. Sympathetic innervation is from the T6-T8 portion of the greater splanchnic nerves via the celiac ganglion and celiac plexus. Visceral referred pain from the gallbladder reaches levels T6-T8 levels via visceral afferent fibers that travel with the greater splanchnic nerves Biliary pain is referred to the T6 – T8 dermatomes within the upper quadrants and epigastric region of the abdomen. Gallstones (cholelithiasis) (Netter 280a) are formed by solidification of bile constituents and composed chiefly of cholesterol crystals, usually mixed with bile pigments and calcium. Stones may become lodged in the fundus of the gallbladder where they may ulcerate through the wall into the transverse colon or duodenum. In the former case they are passed naturally into the rectum but in the latter case they may be held up at the ileocecal junction producing an intestinal obstruction. Gallstones may also become lodged in the cystic or common bile ducts where they obstruct bile flow to the duodenum leading to cholecystitis or jaundice, respectfully, or at the hepatopancreatic ampulla where they block both the biliary and pancreatic duct systems. In this case, bile may enter the pancreatic duct system, causing pancreatitis. Cholecyctitis (see image) is an inflammation of the gallbladder caused by obstruction of the cystic duct by gallstones. The trapped bile causes irritation and pressure build-up in the gallbladder, leading to bacterial infection and perforation and causing pain in the upper right quadrant and epigastric region, fever, nausea and vomiting. Gall stones may be removed by a surgical procedure known as cholecystectomy.

Pancreas (Netter 281, 284; Moore 265-268)

   The pancreas has two functions:

1. digestive – produces digestive enzymes
2. hormonal – islets of Langerhans produce insulin and other hormones needed to control blood sugar levels

It lies posterior to the stomach and posterior to the peritoneum of the abdominal cavity and is considered a “secondarily retroperitineal” structure. It is divided into a head, neck, body, and tail. The head of the pancreas lies in the “C” shaped portion of the duodenum.  There is a small projection from the head of the pancreas which is called the uncinate process. A perforated gastric ulcer may result in adhesions between the stomach and pancreas with subsequent erosion into the pancreatic parynchyma and resultant pancreatitis.  The neck of the pancreas is more constricted than the head. The body runs from the right to left connecting the neck to the tail, which lies at the hilus of the spleen. The tail projects into the lienorenal (splenorenal) ligament.

The pancreas develops from both a ventral and a dorsal bud (see lecture on GI Development). The distal portion of the duct of the dorsal bud joins the duct of the ventral bud to form the main pancreatic duct or “Duct of Wirsung”. The remaining portion of the duct of the dorsal bud (if it persists) is the “Duct of Santorini” (Netter 281).

Duct System (Netter 280) The common bile duct, formed by the union of the cystic duct and the hepatic duct, joins the pancreatic duct just as it enters the duodenum, 8-10 cm. below the pylorus. The common bile duct and the main pancreatic duct enter the duodenum together and form a small ampulla, the “Ampulla of Vater”. The ampulla opens into the duodenum at the duodenal papilla. A sphincter muscle, the “Sphincter of Oddi”, closes the ampulla when bile is not to be released into the duodenum. An accessory papilla, if present from the duct of Santorini, lies 1-2 cm. above the duodenal papilla. Blood Supply (Netter 284, 286) The arterial supply is from both the celiac trunk and the superior mesenteric artery. The superior pancreaticoduodenal artery usually arises from the gastroduodenal artery (from the celiac trunk) and then bifurcates into anterior and posterior branches which supply the head of the pancreas and the duodenum. These arcades anastamose iwth those from the inferior pancreaticoduodenal artery, a branch of the superior mesenteric artery. The great pancreatic artery, caudal pancreatic arteries and and occasional dorsal pancreatic artery arise from the splenic artery and supply the body and tail of the pancreas. Pancreatic veins drain into the hepatic portal system through the superior mesenteric vein as well as the common hepatic and splenic veins. To view a cross section through the Abdomen showing the liver, spleen and biliary system click here

 

Clinical Correlation The pancreas develops from two buds, a ventral and a dorsal bud, and may develop abnormally resulting in an accessory pancreas or an annular pancreas. An annular pancreas results if the ventral pancreatic bud divides into two with the two pieces migrating in opposite directions to form a ring around the duodenum. The clinical result is constriction of the duodenum. The pancreas is not usually subject to damage resulting from trauma with the exception of gastric surgery where the pancreas may be accidently damaged. Spasms of the sphincter of Oddi, (the sphincter which controls the flow of bile from the glaa bladder into the cystic duct) at the ampulla may result in the regurgitation of bile into the pancreas resulting in an acute and severe inflammation, pancreatitis. Spasm of the hepatopancreatic sphincter or blockage of the duct at the duodenal papilla by a gallstone not only results in biliary stasis, but may also cause reflux of bile into the pancreas. This situation activates the pancreatic enzymes with resultant acute pancreatitis. Carcinoma of the pancreas is common. The prognosis for recivery is usually poor because metastases may spread widely yalong retroperitoneal lymphatic channels. Fully 80% of pancreatic cancers are located in the head. Jaundice with no indication of biliary pathology or hepatic dysfunction may result from compression of the common bile duct by a pancreatic tumor. Pancreatic cancer frequently invades the splenic vein and even the portal vein, manifesting as symptoms of portal hypertension, such as esophageal varices without indications of liver disease. Remember the three rules of surgery (from Dana Stearns): Eat when you can Sleep when you can and never *%&# with the pancreas! (because it is so vascular)