HBF-II LEC 49 Gross Anatomy Duodenum Pancreas Spleen Notes 2024 PDF

Gross Anatomy: Duodenum, Pancreas & Spleen Page 1 of 19 Dr. Dennis Goebel LEARNING OBJECTIVES 1. Describe the duodenum: divisions, peritoneal recesses, arterial supply, venous and lymphatic drainage, innervation, and clinical relevancies. 2. Describe the...

Gross Anatomy: Duodenum, Pancreas & Spleen Page 1 of 19 Dr. Dennis Goebel LEARNING OBJECTIVES 1. Describe the duodenum: divisions, peritoneal recesses, arterial supply, venous and lymphatic drainage, innervation, and clinical relevancies. 2. Describe the pancreas: divisions, ducts, arterial supply, venous and lymphatic drainage, innervation, and clinical relevancies. 3. Describe the spleen: surfaces, peritoneal relationships, arterial supply, venous and lymphatic drainage, innervation, and clinical relevancies. SESSION OUTLINE I. Duodenum A. General description B. Divisions of the Duodenum 1. Superior division (1 st part) a. Subdivisions of the superior division i. Proximal part (Duodenal cap) ii. Distal part b. Anatomical relationships of the superior division of the duodenum 2. Descending Division of the duodenum (2nd part) a. General description b. Relationship of the bile and main pancreatic ducts and the hepatopancreatic ampulla & major duodenal papilla to the 2 nd part of the duodenum. c. Anatomical relationships of the descending division of the duodenum 3. Horizontal division of the duodenum (3 rd part) a. General description b. Anatomical relationships 4. Ascending division of the duodenum (4 th part) a. General description b. Anatomical relationships C. Peritoneal Recesses of the Duodenum 1. General descriptions a. Peritoneal folds and recesses associated with the duodenal-jejunum junction i.. Inferior duodenal fold and recess ii. Superior duodenal fold and recess iii. Paraduodenal fold and recess iv. Retroduodenal recess Gross Anatomy: Duodenum, Pancreas & Spleen Page 2 of 19 Dr. Dennis Goebel D. Arterial Supply of the duodenum E. Venous Drainage of the Duodenum F. Lymphatics of the Duodenum G. Innervation of the Duodenum H. Clinical Correlates of the Duodenum 1. Duodenal ulceration of the 1 st part 2. Internal herniation II. Pancreas A. General descriptions and functions. B. Subdivisions of the Pancreas 1. Head of the pancreas 2. Neck of the pancreas 3. Body of the pancreas 4. Tail of the pancreas C. Pancreatic Ducts 1. Main pancreatic duct 2. Accessory pancreatic duct D. Arterial Supply of the Pancreas E. Venous Drainage of the Pancreas F. Lymphatics of the Pancreas G. Innervation of the Pancreas H. Clinical Correlates of the Pancreas III. Spleen A. Surfaces of the Spleen B. Peritoneal Relations of the Spleen C. Arterial Supply of the Spleen D. Venous Drainage of the Spleen E. Lymphatics of the Spleen F. Innervation of the Spleen G. Clinical Correlates of the Spleen Supplemental Reading: Gray’s Anatomy for Students, 4th Ed (2020) Drake, Vogl, Mitchell. Chapter 4: Abdomen Gross Anatomy: Duodenum, Pancreas & Spleen Page 3 of 19 Dr. Dennis Goebel Introduction: The small intestine is the longest part of the GI tract and extends from the pyloric orifice of the stomach to the ileocecal valve. This hollow tube measures 6-7 meters in length, with the diameter narrowing from beginning to end. Anatomically the small intestine is divided into three parts that are defined as the duodenum, jejunum and ileum. In this presentation, I will be describing the duodenum and associated organ structures (e.g. the pancreas and the bile and pancreatic duct systems. In addition, the spleen (a non-digestive organ) will be discussed. Description of the jejunum and ilium will be presented in a separate enrichment presentation, which will also cover the divisions of the large intestine. I. The duodenum is the first part of the small intestine and participates in both digestion and absorption (uptake) of the emulsified chyme passing from the stomach. It receives bile produced by the liver, and enzymes secreted from the pancreas. A. The duodenum begins at the pylorus and ends at the duodeno-jejunal junction. It is approximately 25 cm in length and is mostly a retroperitoneal structure that is associated with the posterior abdominal wall, between the lumbar vertebrae levels LV1-LV3. This C-shaped structure courses laterally around the head of the pancreas on the right side, before crossing anterior to the inferior vena cava (IVC) and aorta to the left side, where it will then transition into the jejunum at the duodeno-jejunal flexure (See Figure 1 below). Figure 1 B. Divisions of the duodenum: The duodenum consists of 4 anatomically defined regions, superior (1st part), descending (2nd part), transverse (3rd part), and ascending (4tt part) (See Figures 1 & 2). Gross Anatomy: Duodenum, Pancreas & Spleen Page 4 of 19 Dr. Dennis Goebel 1. Superior part (1st part): The superior part of the duodenum is positioned on the right side of the posterior abdominal wall, anterolateral to the body of LV1. It is a peritoneal structure (e.g. suspended by a mesentery off of the posterior abdominal wall and by the hepatoduodenal ligament [See figure 3]) measuring approximately 5 cm in length, and is the most movable part of the duodenum. a. The superior part of the duodenum is subdivided into proximal and distal regions: Figure 2 i. The proximal part of the superior duodenum has a smooth luminal surface (easily identified by contrast CT imaging). This area is referred to as the duodenal ampulla or duodenal cap/bulb (See Figure 2). a. The proximal part of the superior duodenum is suspended by the greater omentum and t h e hepatoduodenal ligament, hence this part moves with the stomach. b. Due to the direct exposure to acidic chime being passed from the stomach, the initial part of the duodenum is the most vulnerable part of the small intestine to erosion/ulceration. ii. The distal part of the superior duodenum has a corrugated luminal surface (permanent folds), and becomes retroperitoneal (e.g., fixed to the posterior abdominal wall). See Figure 2. b. Anatomical Relationships of the Superior Part of the Duodenum i. Anterior a. Peritoneum cavity b. Gall bladder Gross Anatomy: Duodenum, Pancreas & Spleen Page 5 of 19 Dr. Dennis Goebel c. Quadrate lobe of the liver ii. Posterior a. Bile duct b. Portal vein c. Inferior vena cava d. Gastroduodenal artery iii. Superior a. Neck of the gall bladder iv. Inferior a. Mostly the neck region of the pancreas Figure 3 2. The descending part (2nd part) of the duodenum measures apx 7.5 cm in length and is fixed to the posterior abdominal wall (i.e, is retroperitoneal). It descends along the right side of the bodies of LV1 to LV3 and the inferior vena cava. a. The bile duct & main pancreatic duct enter the posteromedial wall of the descending part of the duodenum, at approximately 2/3 along its length. These ducts usually unite to form the hepatopancreatic ampulla (also known as the “ampulla of Vater”). The hepatopancreatic ampula terminates in the lumen of the descending duodenum on it inferior medial Gross Anatomy: Duodenum, Pancreas & Spleen Page 6 of 19 Dr. Dennis Goebel wall, as the major duodenal papilla (See Figure 4A & B). i. The opening of the hepatopancreatic ampulla is encircled by the sphincter of the hepatopancreatic ampulla ( See Figure 4B). Figure 4 b. Anatomical Relationships of the Descending Part of the Duodenum (See Figures 1 & 3) i. Anterior a. transverse colon b. transverse mesocolon c. some coils of the small intestine ii. Posterior a. hilus of the right kidney b. rt renal arteries and veins c. right ureter d. right psoas major muscle iii. Medial a. head of the pancreas b. pancreatic duct c. bile duct 3. Horizontal part of the duodenum (3rd part) is about 10 cm long and courses retroperitoneally on a horizontal plane (from the right to left side of the posterior abdominal wall) at the level of LV3. In its course, it passes anterior to the inferior vena cava and aorta, and posterior to the superior mesenteric artery and vein (See Figures 1 & 3). a. Relationships of the Horizontal Part of the Duodenum (See Figures 1 & 3) i. Anterior a. Superior mesenteric a. & v. b. Coils of the small intestine c. Root of the mesentery Gross Anatomy: Duodenum, Pancreas & Spleen Page 7 of 19 Dr. Dennis Goebel ii. Posterior a. Right psoas major b. Inferior vena cava c. Aorta d. Right ureter iii. Superior a. Head of the pancreas b. Superior mesenteric vessels 4. Ascending part of the duodenum (4 th part): The ascending part of the duodenum is about 2.5 cm long and ascends on the left side of the aorta at the level of LV2. Most of ascending duodenum is retroperitoneal (immobile), with only the most distal part becoming a peritoneal. It is at this point where the duodenum transitions into the jejunum, by making a sharp anterior-inferior bend that defines the duodenojejunal flexure (See Figures 1-3). a. The duodenojejunal flexure is supported by a fibromuscular structure called the suspensory muscle (or ligament) of the duodenum. The suspensory muscle of the duodenum arises from the right crus of the diaphragm and attaches to the ascending part of the duodenum. Its purpose is to restrict the mobility of the 4 th part of the duodenum. b. Anatomical Relationships of Ascending Part of Duodenum (See Figures 1 & 3) i. Anterior a. Beginning of the root of the mesentery b. Coils of jejunum ii. Posterior a. Left psoas major muscle b. Left margin of the aorta iii. Medial a. Head of the pancreas b. Superior mesenteric artery and vein iv. Superior: b. Body of the pancreas C. Peritoneal Recesses of the Duodenum 1. Several peritoneal folds and recesses are related to the duodenum. Most of them are incessant (variable). The folds and recesses are formed when the structures transition from being retroperitoneal to peritoneal, or vice versa. The most clinically significant area involves the region where the ascending duodenum (retroperitoneal) transitions to the jejunum (peritoneal). a. In this region there are 3 defined folds and four recesses: See Figure 5 i. Superior duodenal fold and recess ii. Inferior duodenal fold and recess iii. Paraduodenal fold and recess (this fold contains the inferior mesentery Gross Anatomy: Duodenum, Pancreas & Spleen Page 8 of 19 Dr. Dennis Goebel vein within it). iv. Retroduodenal recess: This area is located along the lateral-inferior wall of the ascending part of the duodenum, where the peritoneum reflects from it, to the posterior abdominal wall. This region is positioned between the between Superior and Inferior duodenal folds duodenal, and their corresponding recesses (Figure 5). Figure 5 D. Arterial Supply of the Duodenum 1. The duodenum has a rich blood supply. The main blood supply to the duodenum is from the gastroduodenal and inferior pancreaticoduodenal (PD) arteries (the latter, is a branch from the superior mesenteric artery). See Figure 6. a. The proximal half of the duodenum is supplied by the gastroduodenal artery and distal half by the inferior PD artery. i. Superior (supplied by the Celiac trunk) and inferior PD arteries (supplied by the superior mesenteric artery) anastomose in the head of the pancreas by forming anterior and a posterior pancreaticoduodenal arterial arcades. These provide straight arteries that supply the descending and transverse parts of the duodenum, as well as provide the major source of blood supply to the head and neck of the pancreas. ii. The first part of the duodenum receives its blood supply from the supraduodenal artery, which is supplied by the celiac trunk (Figure 6). Gross Anatomy: Duodenum, Pancreas & Spleen Page 9 of 19 Dr. Dennis Goebel The origin of this artery is variable (e.g. and can come off of the gastroduodenal, right gastric, or proper hepatic arteries). E. Venous drainage of the Duodenum Generally, the veins follow the arteries and drain into the hepatic portal venous system via the superior mesenteric and the right gastric veins. F. Lymphatics of the Duodenum (See Figure 7 on the next page) 1. Pancreaticoduodenal nodes (along pancreaticoduodenal arteries) 2. Pyloric nodes (along gastroduodenal A.) 3. Superior mesenteric nodes (along superior mesenteric A.) Gross Anatomy: Duodenum, Pancreas & Spleen Page 10 of 19 Dr. Dennis Goebel Figure 7 G. Innervation of the Duodenum 1. Autonomic nerves from the vagus (PANS) and postganglionic sympathetic (SANS) nerves from the prevertebral (e.g. celiac & superior mesenteric) ganglia. Recall that the prevertebral (SANS) ganglia receive their preganglionic innervation from the thoracic splanchnic (greater, lesser and least) nerves. 2. Autonomic nerves travel to the duodenum along the arteries that supply it (mostly pancreaticoduodenal arteries). H. Clinical Correlates of the Duodenum 1. The first part of the duodenum is most prone to ulceration. If the ulcer becomes perforated (erodes through the wall), digestive juices and gut contents can escape into the peritoneal cavity and produce peritonitis (inflammation of the peritoneum). 2. Internal hernia: During embryological development of the duodenum and the pancreas, these organs were initially suspended off of the posterior abdominal wall mostly by the dorsal mesentery (i.e., were originally defined as being peritoneal). Through the rapid growth and rotation of the alimentary tract, most of these structures were repositioned against the posterior abdominal wall to become retroperitoneal structures. Because of this, there exists a fascial-plane between the posterior wall and these structures that is vulnerable to blunt dissection by neighboring coils of jejunum and ilium. Gross Anatomy: Duodenum, Pancreas & Spleen Page 11 of 19 Dr. Dennis Goebel a. According to the literature1, the region defined by the superior-, inferior- and paraduodenal-folds and their corresponding recesses (See Figure 5), is the most common site for internal-herniation within the peritoneal cavity. Invasion by the jejunum/ilium in the underlying recesses, described above, can create a peritoneum-lined cavity that can invade the fascial plane underlying the neighboring retroperitoneal organs (e.g. pancreas & duodenum), and the posterior abdominal wall. If acute, normally these hernias will go undetected, however in cases where the hernia increases in size (containing more of the small intestine), there is the possibility whereby the herniated coils of the small intestine could twist and become strangulated within the hernia and undergo ischemia. This is an incredibly painful condition (and life-threatening) and will require emergency surgery. b. In repairing the hernia, one has to be mindful not to accidently cut the paraduodenal fold in retracting the herniated small intestine, as this fold contains the inferior mesenteric vein (IMV). It is important to note that the portal venous system lack valves, and that cutting into the IMV, will result in massive bidirectional venous hemorrhaging, with most of this outflow coming from the liver. c. The incidence of internal herniation is believed to result mostly from congenital defects1. II. The Pancreas: The pancreas is an elongated soft tissue digestive/endocrine gland, which is associated with the posterior abdominal wall. It is mostly a retroperitoneal structure (with the exception of its tail) that lies posterior to the omental bursa (lesser sac) and transverses the posterior abdominal wall between the levels of LV1-LV3 (See Figure 1). The pancreas serves as both an exocrine gland secreting trypsin, chymotrypsin (both proteases); amylase (carbohydrate digestion) and lipase (digestion of fats) that enters duodenum by way of the pancreatic ducts; and as an endocrine gland (involved in releasing insulin and glucagon to regulate glucose blood levels). A. Subdivisions of the pancreas: The pancreas is anatomically divided into the head, neck, body and tail (See Figure 1). 1. Head of the pancreas a. The head of the pancreas is retroperitoneal and is contained by the curve of the duodenum (descending, transverse and ascending parts). The head of the pancreas courses posterior-medially and encircles the superior mesenteric artery and vein on the right side and terminates as a wedge- shaped extension that passes posterior to the superior mesenteric artery and vein. This region of the pancreas is referred to as the uncinate process (See Figure 1). b. The following structures are posterior to the head of the pancreas (Figure 8). i. Inferior vena cava ii. Right renal vessels iii. Bile duct Gross Anatomy: Duodenum, Pancreas & Spleen Page 12 of 19 Dr. Dennis Goebel Figure 8 2. Neck of the pancreas a. The neck of the pancreas is retroperitoneal and defined as the region of the pancreas that passes ventral to the superior mesenteric vein and artery (See Figure 1). b. It is approximately 2 cm long, and grooved on its dorsal surface by the superior mesenteric vessels. This region is positioned between the head and the body of the pancreas. c. Its anterior surface is covered with peritoneum and is adjacent to the pylorus of the stomach. d. The portal vein forms from the merger of splenic and superior mesenteric veins posterior to the neck of the pancreas. 3. Body of the pancreas a. The body of the pancreas is also retroperitoneal. It crosses the aorta and extends laterally between vertebral levels LV1-LV3 on the left side of the posterior abdominal wall (See Figure 1). b. It is posterior to the omental bursa (lesser sac). c. Its superior margin is intimately associated with the splenic artery. Gross Anatomy: Duodenum, Pancreas & Spleen Page 13 of 19 Dr. Dennis Goebel 3. Relationships of the Body of the Pancreas i. Anterior surface a. Covered by peritoneum (posterior wall of the lesser sac (omental bursa)) b. Bed of the stomach c. Attachment for the transverse mesocolon along its ventral surface. ii. Posterior surface a. Aorta b. Superior mesenteric artery c. Left suprarenal gland d. Left kidney 4. Tail of the pancreas a. The tail of the pancreas is a short (~2 cm) peritoneal structure that is suspended off of the posterior abdominal wall within the splenorenal ligament. b. Its tip usually comes in contact with the hilum of the spleen (See Figure 1). C. Pancreatic Ducts: The pancreas contains a main pancreatic duct and an accessory pancreatic duct (See Figure 9). 1. Main Pancreatic Duct a. It begins at the tail of the pancreas and runs through the substance of the gland, receiving tributaries from the tail, body and neck, uncinte and part of the head of the pancreas. b. Within the head of the pancreas the main duct turns inferiorly and usually unites with the bile duct to form the hepatopancreatic ampulla. i. The hepatopancreatic ampulla opens into the lumen of the duodenum (on its medial wall) via the major duodenal papilla. c. Regulation of flow into the hepatopancreatic ampulla (also known as the “ampulla of Vater”) (Figure 9 on the next page). i. Bile flow into the ampula is controlled by a smooth muscle valve called the sphincter of the (Common) bile duct (also called the choledochal sphincter) surrounds the terminal part of the bile duct (See Figure 4B). ii. A dedicated sphincter controlling the flow of the main pancreatic duct into the hepatopancreatic ampulla is not well defined (See Figure 4B). iii. Sphincter controlling flow from the hepatopancreatic ampula into the lumen of the descending part of the duodenum (on its posterior-medal wall is called the hepatopancreatic sphincter (See Figure 4B). Gross Anatomy: Duodenum, Pancreas & Spleen Page 14 of 19 Dr. Dennis Goebel 2. Accessory pancreatic duct: It drains part of the head of the pancreas. In most cases, it forms a connection, and drains directly into the main duct (Figure 9). However, according to the literature, in 50% of the population the accessary pancreatic duct maintains it embryological connection to the 2nd part duodenum and remains patent. When present, the accessory pancreatic duct enters the medial wall of the 2 nd part of the duodenum apx 1.5 cm superior to the entrance of the main pancreatic/bile duct) in ~50% of the population2. This duct empties into the duodenum through the minor duodenal papilla (See Figure 10). Figure 9 Figure 10 D. Arterial Supply of the Pancreas 1. The pancreas receives arterial supply from branches coming from the celiac and superior mesenteric arteries. Celiac branches include the splenic, the superior pancreaticoduodenal arteries and the superior mesenteric artery provides the inferior pancreatico-duodenal artery See Figures 6 & 8. Gross Anatomy: Duodenum, Pancreas & Spleen Page 15 of 19 Dr. Dennis Goebel a. Splenic artery: Gives rise to multiple small branches that supply the body and tail of the pancreas (you will not be responsible for individually identifying them in this course). b. Anterior & posterior pancreaticoduodenal arteries: These form a pair (an anterior and posterior branch) of arcades than anastomose in the head of pancreas, and supply the head and neck regions of the pancreas, and to most of the duodenum (See Figure 8). E. Venous Drainage of the Pancreas: The pancreatic veins drain into the, splenic and superior mesenteric veins (hepatic portal system). F. Lymphatics of the Pancreas: The lymph produced by the pancreas drains into lymph nodes that are regionally directed to the celiac, the hepatic or the superior mesenteric lymph nodes. G. Innervation of the Pancreas 1. Autonomic nerves from the vagus (parasympathetic) and postganglionic sympathetic nerves from the prevertebral ganglia (e.g. celiac & superior mesenteric) provide innervation to the pancreas. The sympathetic ganglia receive their preganglionic innervation mostly from the greater splanchnic nerve. 2. Because the preganglionic SANS fibers innervating the celiac ganglia arise from the splanchnic nerves, visceral afferent signals (pain) from the pancreas travel back to the spinal cord via the greater splanchnic nerve. a. Pain resulting from inflammation of the pancreas (termed pancreatitis) is usually referred to the anterior upper abdomen (gastric region) and can spread to the back. 3. The postganglionic sympathetic fibers coming from the celiac and superior mesenteric ganglia, together with the parasympathetic fibers from vagus, utilize the surface of the arteries supplying these organs, to reach their visceral targets. Likewise, visceral afferents utilize the arterial vasculature to make their way back to their corresponding spinal cord level(s). H. Clinical Correlates of the Pancreas 1. Malignant tumors of the pancreas occur most frequently in the regions of the head and neck. 2. Gallstone blockage in the hepatopancreatic ampulla is a major cause for inducing pancreatitis (defined as inflammation of the pancreas). 3. Obstruction of the bile duct in pancreatic cancer may cause obstructive jaundice. 4. Surgical removal of a pancreatic tumor is a very complex procedure and usually involves resection of the duodenum and other parts of the GI tract. This is necessary because the arterial supply to the descending, transverse and ascending duodenum, and the head of the pancreas, share blood supply via the anterior and posterior pancreatic duodenal arteries. Since most pancreatic cancers are localize to the head and neck region of the pancreas, surgical removal of both the head of the pancreas and the adjoining descending, transverse and ascending portion of the duodenum is performed. This surgical procedure is called the “Whipple surgical procedure” originated in back in 1939, and continues to be refined to improve better outcome and quality of life (look for it in lab). Gross Anatomy: Duodenum, Pancreas & Spleen Page 16 of 19 Dr. Dennis Goebel III. SPLEEN A. The spleen is a large and highly vascular lymphatic organ that is located in the left upper quadrant of the abdomen. It is the largest single mass of lymphoid tissue in the body. 1. The spleen is a peritoneal structure that is suspended off of the posterior abdominal wall by the splenorenal ligament and is attached to the greater curvature of the stomach by the gastrosplenic ligament. Both ligaments attach to the spleen on its medial surface (See Figure 11). Figure 11 2. It contains a medial orientated visceral surface and a laterally orientated smooth diaphragmatic surface. a. Visceral Surface (See Figures 12 & 13) i. Contains the hilum where arterial supply venous return and lymphatic ducts enter and exit the spleen. iii. Contains impressions made by the neighboring stomach and the left colic flexure (See Figures 12 & 13). Gross Anatomy: Duodenum, Pancreas & Spleen Page 17 of 19 Dr. Dennis Goebel iii. Is in contact with the posterior wall of the stomach, the tail of the pancreas and the splenic flexure of the colon. iv. It is connected to the greater curvature of the stomach by gastrosplenic ligament. v. It is attached to the posterior abdominal wall by the splenorenal ligament (a mesentery that overlies the region of the superior pole of the left kidney). b. Diaphragmatic Surface (See Figure 12) i. It is convex and smooth. ii. It contacts diaphragm at the level of ribs 9-11. Figure 12 3. Arterial Supply of the Spleen a. The spleen is supplied by the splenic artery (See Figures 6 & 13). i. It follows a tortuous course along the superior border of the pancreas. ii. Between the layers of the splenorenal ligament, the splenic artery divides into 5 or more branches, which enter the hilum of the spleen. Gross Anatomy: Duodenum, Pancreas & Spleen Page 18 of 19 Dr. Dennis Goebel Figure 13 4. Venous drainage of the Spleen (See Figures 12 & 13) a. The splenic vein is formed by several tributaries that emerge from the hilum of the spleen, and from the left side of the greater curvature of the stomach (e.g. short gastric and the left gastro omental veins). b. The splenic vein receives venous drainage from several small veins exiting the pancreas along its route before being joined by the inferior mesenteric vein. c. The splenic vein courses posterior to the tail and the body of the pancreas and joins with the superior mesenteric vein to form the portal vein near the neck of the pancreas. 5. Lymphatics of the Spleen a. Splenic lymph vessels drain into the pancreaticosplenic lymph nodes, which are present along surface of the superior border of the pancreas. 6. Innervation of the Spleen a. Most of the autonomic innervation of the spleen is involved in vasoconstriction. Postganglionic sympathetic are provided by the Celiac ganglion and parasympathetic fibers present originate from the Vagus N. Both utilize the outer surface of the splenic artery to make their way to the spleen. Gross Anatomy: Duodenum, Pancreas & Spleen Page 19 of 19 Dr. Dennis Goebel 7. Clinical Correlations of the Spleen a. The spleen is the most frequently ruptured abdominal organ in the body, with rib fracturing (ribs 9 and/or 10) being the most common cause. A rupture spleen is life-threatening and usually results in severe intraperitoneal hemorrhaging that can lead to shock. b. Some diseases result in enlargement of the spleen (called “splenomegaly”). An enlarged spleen crowds other abdominal viscera and cause abdominal pain and discomfort. Under extreme conditions, removal of the spleen is necessary. c. The spleen can be removed without causing major problems to adult human health. d. The splenic artery branches entering the spleen do not anastomoses. Consequently, obstruction of an individual arterial branch would result in necrosis of the splenic tissue that was supplied by this vessel. Sources for Figures Atlas of Human Anatomy, 6th Ed. Frank H. Netter, © Sanders/Elsevier, 2014. Gray’s Anatomy for Students, 3rd Edition, R.L. Drake, A.W. Vogl and A.W.M. Mitchell, © Churchill Livingstone//Elsevier, 2015. Gray’s Anatomy for Students 3rd Ed., © Churchill Livingstone/Elsevier, 2015 References: 1 Takeyama N., et al., CT of Internal Hernias, Radio Graphics (2005), 25(4): 997-1015. 2 Prasanna LC, et al., Accessory Pancreatic duct patterns and their implications, J. Clinical & Diagnostic Research, (2015) 9(3): 5-7.