Peritoneal Cavity & Viscera of the Abdomen PDF

Peritoneal Cavity DPM Program Learning Objectives: 1. 2. 3. 4. Distinguish the parietal and visceral peritoneum and explain where the peritoneal cavity is located. Explain the difference between the peritoneal ligaments, mesenteries and omenta. Distinguish intraperitoneal, primarily retroperitonea...

Peritoneal Cavity DPM Program Learning Objectives: 1. 2. 3. 4. Distinguish the parietal and visceral peritoneum and explain where the peritoneal cavity is located. Explain the difference between the peritoneal ligaments, mesenteries and omenta. Distinguish intraperitoneal, primarily retroperitoneal, and secondarily retroperitoneal organs. Describe the boundaries of the lesser and greater peritoneal sacs and the relationship of the lesser sac to the epiploic foramen. 5. Describe pain referral patterns of the abdominal viscera. 6. Discuss the removal of ascites from the peritoneal cavity (paracentesis). 7. Discuss the location of the hepatorenal recess (Morrison’s pouch) and the conditions that can affect it. 8. Describe the portal triad and the duct system for the passage of bile from the liver to the duodenum, and for storage in the gallbladder. 9. Describe the course of the major branches of the abdominal aorta, venous drainage to the inferior vena cava and portal vein, and lymphatic drainage from the viscera. 10. Discuss the autonomic and visceral sensory innervation of the visceral organs in the abdominal cavity. 11. Describe the structure and function of the gastrointestinal abdominal viscera and spleen. 12. Describe the location of the appendix with respect to surface landmarks of the abdomen. 1 SMU - Internal Data Distinguish the parietal and visceral peritoneum and explain where the peritoneal cavity is located. Peritoneum: -serous lining of the abdominal cavity. Divided into: 1) Parietal peritoneum -lines the walls of the abdominal cavity 2) Visceral peritoneum -reflects from the body wall and covers the intraperitoneal viscera -serves as a conduit for their neurovascular supply 2 SMU - Internal Data Describe the boundaries of the lesser and greater peritoneal sacs and the relationship of the lesser sac to the epiploic foramen. Peritoneal Cavity -Space between parietal and visceral layers of peritoneum -Subdivided into 2 sacs: Greater sac • From the diaphragm to pelvic cavity • 2 compartments: • Supracolic-above transverse mesocolon, • Contains: stomach, liver, spleen • Infracolic-below transverse mesocolon • Contains: small and large intestines Lesser sac (omental bursa) • Posterior to the stomach • Anterior to the pancreas and duodenum • Allows unrestricted movement of the stomach Between the 2 sacs is a passageway called the epiploic foramen (omental foramen) • Posterior to the hepatoduodenal ligament 3 SMU - Internal Data Distinguish intraperitoneal, primarily retroperitoneal, and secondarily retroperitoneal organs. Abdominal viscera can be divided into those that are: 1) Intraperitoneal (peritonealized) -suspended in the abdominal cavity by reflections of visceral peritoneum called mesenteries 2) Retroperitoneal -structures have no mesenteries -outside of the parietal peritoneum 4 SMU - Internal Data Intraperitoneal Organ Structures Retroperitoneal Organ Structures Structures Associated Peritoneal Reflection Duodeum (parts 2, 3, & 4) Stomach Greater omentum (Gastrocolic, Gastrosplenic, & Gastrosplenic ligaments) Lesser omentum (Hepatogastric Ligament) Ascending Colon Duodenum (1st part) Lesser omentum (Hepatoduodenal Ligament) Rectum Jejunum Mesentery Proper Ileum Mesentery Proper Aorta (& origins of its paired and unpaired visceral branches) Cecum Cecal Folds Inferior Vena Cava Appendix Mesoappendix Kidneys and Ureters* Transverse Colon Transverse Mesocolon Suprarenal Glands Sigmoid Colon Sigmoid Mesocolon Spleen Gastrosplenic Ligament Liver and Gallbladder Lesser omentum, Falciform Ligament Pancreas (tail) Splenorenal Ligament Uterus and Uterine Tubes* Broad Ligament* Ovaries* Broad Ligament* SMU - Internal Data Descending Colon Pancreas (Head, Neck, and Body) 5 * Note these structures will be discussed during subsequent lectures Discuss the removal of ascites from the peritoneal cavity (paracentesis). Ascites -Accumulation of more than 20 mm of fluid within the peritoneal cavity Causes: -Increased pressure in the hepatic portal vein (portal hypertension). Associated with liver cirrhosis. Presents as a: -Bulging belly, when struck waves of moving fluid Treatment: -Drain fluid via surgical puncture Location: 2cm below umbilicus in the midline through linea alba or, 5 cm superior and medial to the anterior superior iliac spines on either side -Important to treat because can lead to peritonitis -inflammation of the peritoneum -can be caused by intestinal bacteria which get to the peritoneum via lymph -treated with antibiotics 6 SMU - Internal Data Explain the difference between the peritoneal ligaments, mesenteries and omenta. These terms are used to describe certain visceral mesenteries. Mesenteries help to maintain the position of viscera and serve as conduits for vessels, nerves and lymphatics. 7 SMU - Internal Data Omenta Omenta: folds of peritoneum which bind viscera to other viscera, or to the abdominal wall. Liver Stomach Hepatogastric ligament Hepatoduodenal ligament Greater omentum Stomach Duodenum Greater Omentum (outlined in green) -Arises from the greater curvature of the stomach and free section of the transverse colon SMU - Internal Data Lesser Omentum (outlined in red) Has 2 parts: 1) Hepatogastric (liver to stomach) 2) Hepatoduodenal (liver to duodenum; deep to it we find the portal triad) 8 Mesenteries Mesentery -store fat, vessels, nerves and attach intestines to the abdominal wall Different mesenteries: 1) Transverse Mesocolon • From transverse colon to posterior abdominal wall • Contains: • Middle colic artery and vein • Marginal artery and vein 2) Sigmoid Mesocolon • Sigmoid colon to pelvic wall • Contains: • Sigmoid arteries and veins • Superior rectal artery and vein 3) Mesentery of the Ileum/Jejunum (the Mesentery Proper) • From small intestines (jejunum/ileum) to posterior abdominal wall • Contains: • Superior mesenteric artery and vein • Intestinal branches to Jejunum and Ileum • Autonomic nerve plexuses • Lymphatics • Fat SMU - Internal Data Transverse mesocolon Mesentery proper Sigmoid mesocolon 9 Major Mesenteric Ligaments Gastric Ligaments Mesenteric Ligament Location, Vessels, and Other Associated Abdominal Structures Gastrocolic ligament Where greater omentum inserts at transverse colon Forms anterior boundary of the omental bursa (the lesser sac of the abdomen) Contains: right and left gastroepiploic arteries Gastrophrenic ligament Splenic Ligaments Hepatic Ligaments Splenorenal ligament Connects hilum of spleen with left kidney Transmits: splenic artery and vein Gastrosplenic ligament Greater omentum to spleen Contains: short gastric vessels and left gastroepiploic vessels Hepatogastric ligament Liver to stomach Contains: right and left gastric arteries near the stomach Hepatoduodenal ligament Liver to duodenum Contains Portal triad: hepatic portal vein, common bile duct, and hepatic artery Falciform ligament Anchors the liver, anterior abdominal wall, and diaphragm Contains: Ligamentum teres (obliterated umbilical vein) Small unnamed arteries and veins that serve the ligamentum teres and communicate with abdominal arteries and veins Coronary ligaments Attach liver to the diaphragm, right kidney, and adrenal gland Triangular ligaments Hold the liver in place, bilateral structures 10 SMU - Internal Data Do you remember the yolk sac from early development? During body folding the yolk sac becomes the embryonic foregut, midgut, and hindgut. These “guts” give rise to our gastrointestinal organs and accessory organs. Each gut is supplied by different unpaired arteries off of the abdominal aorta. 11 SMU - Internal Data Describe what structures are found in the foregut of the abdomen. • Pharynx (in neck) • Esophagus (primarily in thorax) • Stomach • Duodenum (proximal to & including the entrance of common bile duct) • Accessory digestive organs – Liver – Gall bladder – Pancreas • Spleen (develops in the foregut region, but not a digestive organ) 12 SMU - Internal Data Name what artery supplies the foregut structures and its approximate vertebral level location. Celiac trunk -supplies structures derived from the foregut -Located at L1 vertebral level The celiac trunk is short and immediately branches into: 1) Left gastric artery 2) Splenic artery 3) Common hepatic artery Celiac trunk (foregut) Superior Mesenteric Artery (midgut) Inferior Mesenteric Artery (hindgut) 13 SMU - Internal Data Describe the branches of the celiac trunk and and what they supply. Celiac trunk 3) Common hepatic artery -At the pylorus of the stomach, divides into: gastroduodenal artery/ proper hepatic artery 1) Left Gastric Artery Proper hepatic artery Gastroduodenal artery -supplies left side of lesser curvature of stomach -anastomoses with right gastric artery of proper hepatic artery 2) Splenic Artery -runs posterior to the superior portion of the pancreas supplies the spleen, the head and tail of the pancreas as well as parts of the stomach. 14 SMU - Internal Data Describe the functions, relationships, arterial supply, venous drainage, and lymphatics of the stomach. Liver Functions: -Chief function is enzymatic digestion-gastric juices are mixed with ingested food and convert it into chyme which is then passed into the duodenum. Relationships: Anterior: diaphragm, liver (left lobe), and anterior abdominal wall Posterior: omental bursa (lesser sac), pancreas, left kidney, adrenal gland, spleen, splenic artery Superior: esophagus and diaphragm Inferior/lateral: transverse mesocolon Arterial supply: Right and left gastric arteries, gastroomental (gastroepiploic) arteries, short gastric arteries, gastroduodenal artery Venous Drainage: hepatic portal, splenic, and superior mesenteric veins Lymphatics: intestinal lymphatic trunk-cisterna chyli-thoracic duct Stomach 15 SMU - Internal Data Describe the anatomical features of the stomach. 16 SMU - Internal Data Describe the arterial supply to the stomach. Blood supply to stomach: 1) Left gastric artery 2) Right gastric artery 3) Left gastroepiploic artery 4) Right gastroepiploic artery 5) Short gastric arteries Left Gastric Artery -to proximal lesser curvature -off celiac trunk Short gastric arteries -to fundus of stomach -off splenic a. Right gastric artery -to lesser curvature of stomach -off proper hepatic a. Left Gastroepiploic Artery -to proximal greater curvature -off splenic a. Right Gastroepiploic Artery -to greater curvature of stomach -off gastroduodenal a. SMU - Internal Data 17 Describe the functions, relationships, arterial supply, and venous drainage of the spleen. Functions: -NOT a digestive organ, largest lymphoid organ -Proliferation and maturation of lymphocytes, degradation of damaged erythrocytes Location: Left hypochondriac region (left upper quadrant) Relationships: Anterior: stomach Posterior: ribs 9-10 Superior: esophagus and diaphragm Inferior: rests on the left colic flexure (splenic flexure) Arterial supply: Splenic artery Venous Drainage: Splenic vein 18 SMU - Internal Data Describe the ligaments of the spleen. Ligaments of the spleen: Gastrosplenic Ligament • Connects spleen to greater curvature of the stomach • Contains: short gastric and gastroomental vessels Splenorenal ligament • Connects spleen to left kidney • Contains splenic vessels 19 SMU - Internal Data Describe the functions, relationships, arterial supply, venous drainage, and lymphatics of the liver. Functions: -Protein synthesis, nutrient storage, bile production, bilirubin metabolism Location: right hypochondrium and epigastric regions (extends Right into the left hypochondrium) Hypochondriac Region Anatomy: Lobes: right, left, caudate, quadrate Surfaces: diaphragmatic, visceral Ligaments: coronary, left triangular, falciform, round ligament Liver LIVER Epigastric Region Arterial supply: Hepatic portal vein (80%), hepatic artery (20%) Venous Drainage: Hepatic veins—inferior vena cava—right atrium Lymphatics: intestinal lymphatic trunk-cisterna chyli-thoracic duct 20 SMU - Internal Data Coronary ligaments Right triangular ligament Diaphragm Left triangular ligament Left lobe Right lobe Falciform ligament Gallbladder Anterior View 21 SMU - Internal Data Inferior vena cava Caudate lobe Porta Hepatis ”the gate to the liver” -portal triad structures pass Quadrate lobe through Gallbladder (Netter, 2014) Visceral Surface 22 SMU - Internal Data Describe the contents of the portal triad. Hepatoduodenal ligament: Thick edge of the lesser omentum. Contains the portal triad: 1) (hepatic) portal vein 2) hepatic artery proper 3) (common) bile duct 23 SMU - Internal Data Hepatic vein Sinusoids Central vein Hepatic artery, portal vein branch, bile ductule) (Netter, 2014) Hepatic artery proper Hepatic portal vein Common hepatic duct 24 SMU - Internal Data Describe the hepatic portal vein and the structures that drain into the hepatic portal vein. Stomach (cut) Liver (cut) VESSELS OF THE PORTAL SYSTEM: The veins from these organs converge via three major pathways: -The superior mesenteric vein (SMV) which drains blood from parts of the duodenum, all of the jejunum and ileum, cecum, ascending colon, and 2/3 of the transverse colon. Hepatic portal vein -The inferior mesenteric vein (IMV) drains blood from the distal 1/3 of the transverse colon, all of the descending colon and sigmoid colon, as well as part of the rectum. -The splenic vein drains the spleen and surrounding areas. These converge into the hepatic portal vein (HPV) Splenic vein Superior mesenteric vein (Netter, 2014) Inferior mesenteric vein 25 SMU - Internal Data Describe the arterial supply to the liver and all associated branches. Right and left hepatic arteries -off proper hepatic artery -right hepatic will give rise to cystic artery to the gallbladder Common hepatic artery -directly off celiac trunk Celiac trunk Hepatic artery proper -off common hepatic artery Gastroduodenal artery -off common hepatic artery (Netter, 2014) 26 SMU - Internal Data PORTAL-CAVAL (SYSTEMIC) ANASTOMOSES Portal-caval (systemic) anastomoses are areas where vessels of the portal venous & systemic venous systems communicate, allowing blood to still drain through one system (typically caval) if there is obstruction/diminished flow/increased pressure in the other (typically portal). These anastomoses are of particular importance in cases of portal hypertension (increased pressure in portal venous system). In more severe cases, an artificial communication (e.g. shunt) may need to be produced to allow drainage, and larger veins are typically used to allow more flow, such as the splenic v. (portal) and L. renal v. (caval). There are four main naturally occurring portal-caval anastomoses: • Inferior esophageal submucosa • Peri-umbilical region • Posterior portions of many secondarily retroperitoneal organs • Inferior rectal/anal canal submucosa 27 SMU - Internal Data Describe the location of the (common) bile duct, what it drains in to and what forms it. Cystic duct Hepatic duct Gallbladder (common) Bile duct Duodenum (Netter, 2014) 28 SMU - Internal Data Describe the functions, relationships, and arterial supply of the gallbladder. Functions: The gallbladder is a storage place for bile produced by the liver. It releases it into the 2nd part of the duodenum when fat enters the small intestine. Location: visceral surface of the right lobe of the liver Path of bile: 1) Bile exits the liver in the right and left hepatic ducts 2) These ducts merge to form the common hepatic duct. 3) The cystic duct (from the gallbladder) merges with the common hepatic duct to form the common bile duct 4) Bile duct travels in the hepatoduodenal ligament to reach the duodenum 5) Prior to opening in the duodenum, the bile duct unites with the main pancreatic duct 6) Together they open into the major duodenal papilla Arterial supply: Cystic artery (from right hepatic artery) 29 SMU - Internal Data TRIANGLE OF CALOT Clinical Importance: -Removal of the gallbladder (laparoscopic cholecystectomy) -During this procedure the right hepatic artery must be identified prior to ligation of the cystic artery. This helps to obtain a ‘critical view of safety’ Contents: Right hepatic artery Cystic artery (typically arises from the right hepatic artery and traverses the triangle to supply the gall bladder) Lymph node Lund (first lymph node of the gallbladder) Boundaries: Medial-Common hepatic duct Inferior/Laterally-Cystic duct Superior-Inferior surface of the liver Mnemonic: 3 C Cystic duct Common hepatic duct Cystic artery 30 SMU - Internal Data Describe the functions, relationships, arterial supply, venous drainage, and lymphatics of the duodenum. Pancreas Functions: -neutralizes acidic gastric juices, mixing of bile and pancreatic enzymes, absorption of water, electrolytes, and nutrients Locations: -C-shaped around the head of the pancreas -L1-L3 level 1st 2nd Sections: Superior (1st part)-above superior duodenal flexure Descending (2nd part)-below inferior duodenal flexure Horizontal (3rd part)-aorta to inferior cava Ascending (4th part)-duodenojejunal flexure 4th 3rd Arterial supply: Superior (anterior, posterior) and inferior pancreaticoduodenal arteries (from gastroduodenal) Venous Drainage: hepatic portal, splenic, and superior mesenteric veins 31 SMU - Internal Data Describe the arterial supply to the duodenum. Gastroduodenal artery Duodenum Anterior and posterior superior pancreaticoduodenal arteries -off gastroduodenal a. SMU - Internal Data Inferior pancreaticoduodenal arteries -off superior mesenteric artery 32 Describe the structures the drain into major duodenal papilla, and the significance of the papilla. Common bile duct -opens into major duodenal papilla Foregut Major duodenal papilla -marks the transition between the foregut and midgut Midgut Main pancreatic duct -opens into major duodenal papilla 33 SMU - Internal Data Describe the sympathetic innervation of the foregut structures of the abdomen. Preganglionic sympathetic nerves to foregut structures originate from the: -T5-T9 cord segments Greater thoracic splanchnic nerve From here the preganglionic fibers enter the: -sympathetic chain via white rami, but pass through the chain ganglia without synapse to form the greater thoracic splanchnic nerve -Greater thoracic splanchnic nerve penetrates the diaphragm to enter the abdomen to synapse with postganglionic neurons within the collateral ganglia specifically the celiac ganglion for foregut. Celiac ganglia Postganglionic fibers leave the: -the celiac ganglion and distribute in perivascular plexuses that follow the branches of the celiac trunk to reach their target viscera 34 SMU - Internal Data Describe the parasympathetic innervation of the foregut structures of the abdomen. Esophagus Preganglionic parasympathetic innervation to foregut structures originate from: -Vagus nerve (CN X); cell bodies are located in the brain stem Anterior vagal trunk (from vagus nerve) Celiac ganglion From here the preganglionic fibers synapse with postganglionic neurons in terminal ganglia located on the surface of the organs or within the walls of foregut viscera. Note: Preganglionic fibers pass through celiac ganglion without synapsing Postganglionic fibers then: -contribute to the abdominal autonomic plexuses to reach their target organ 35 SMU - Internal Data Describe what structures are found in the midgut of the abdomen. •Distal Duodenum (discussed previously) •Ileum •Jejunum •Cecum •Appendix •Ascending colon •2/3 of Transverse colon 36 SMU - Internal Data Describe the location of the superior mesenteric artery and its main branches. Superior mesenteric artery -supplies structures derived from the midgut -Located at L1 vertebral level (1cm below celiac trunk) The superior branches include: 1) Inferior pancreaticoduodenal artery 2) Middle colic artery 3) Right colic artery 4) Ileocolic artery 5) Jejunal and Ileal branches Celiac trunk (foregut) Superior Mesenteric Artery (midgut) Inferior Mesenteric Artery (hindgut) Mnemonic for the superior mesenteric arteries: MRI M: middle colic a. R: right colic a. I: Ileocolic a. 37 SMU - Internal Data Middle colic artery -to transverse colon -right and left branches Superior mesenteric artery Inferior pancreaticoduodenal artery -to pancreas & duodenum Right colic artery -to ascending colon -ascending and descending branches Ileocolic artery -to cecum and ascending colon SMU - Internal Data Jejunal and ileum arteries (approx. 10-12 to to jejunum and ileum) 38 Describe the functions, arterial supply, and venous drainage, of the jejunum & ileum. Functions: -final stages of food digestion -absorption of nutrients Jejunum Arterial supply: superior mesenteric artery -proximal 2/5 of the small intestine Venous Drainage: superior mesenteric vein Ileum -distal 3/5 of small intestine SMU - Internal Data 39 Describe the major differences between the ileum and jejunum. Jejunum Ileum Elaborate circular mucosal folds (plicae circulares) Less elaborate circular mucosal folds (plicae circulares) Duodenum (1st part) Lesser omentum (Hepatoduodenal Ligament) Jejunum Mesentery Proper Ileum Mesentery Proper Cecum Cecal Folds Appendix Mesoappendix Transverse Colon Transverse Mesocolon Sigmoid Colon Sigmoid Mesocolon Spleen Gastrosplenic Ligament Liver and Gallbladder Lesser omentum, Falciform Ligament Pancreas (tail) Splenorenal Ligament Uterus and Uterine Tubes* Broad Ligament* Ovaries* Broad Ligament* 40 SMU - Internal Data Describe the functions, relationships, and locations of the cecum and appendix. the CECUM is a blind pouch, at the beginning of the large intestine, located in the right iliac fossa. • It accepts & stores processed material from the small intestine and moves it towards the colon • both the ileum and the appendix open into the medial aspect of the cecum • The ileum: There is an ileocecal valve at the entrance of the ileum into the cecum. The valve is formed by folds of mucosa at the inner surface of the ileocecal orifice. The valve opens, when the stomach is full, to allow contents to enter. When the cecum is full, the pressure of the cecal contents forces the valve closed The APPENDIX: the position of the appendix is highly variable, although it is usually retrocecal. • The appendix has large masses of lymphoid tissue in its wall. • the appendix has it’s own mesentery (mesoappendix). The appendicular artery runs in it’s free margin • the position of the appendix is highly variable, although it is usually Retrocecal • the surface projection of the base of the appendix can be found at McBurneys point. This spot is 1/3 of the distance between the RIGHT anterior superior iliac spine and the umbilicus SMU - Internal Data • pain from an enflamed appendix is usually referred to the umbilicus (T10 dermatome) • the appendix may function as a safe haven for the beneficial bacteria that inhabit the large intestine. This bacteria can repopulate the gut following an infectious disease that causes diarrhea and flushes out the intestinal flora. 41 Describe the functions, location, arterial supply, and venous drainage, ascending colon. Functions: -storage and transport of feces Locations: -right side of the abdominal wall Ascending colon Arterial supply: Right colic artery (off of superior mesenteric artery) Venous Drainage: Right colic vein Right colic artery -to ascending colon -ascending and descending branches 42 SMU - Internal Data Describe the sympathetic innervation of the midgut structures of the abdomen. Preganglionic sympathetic nerves to midgut structures originate from the: -T10-T11 cord segments Lesser thoracic splanchnic nerve From here the preganglionic fibers enter the: -sympathetic chain via white rami, but pass through the chain ganglia without synapse to form the lesser thoracic splanchnic nerve -Lesser thoracic splanchnic nerve penetrates the diaphragm to enter the abdomen to synapse with postganglionic neurons within the collateral ganglia specifically the superior mesenteric ganglion for midgut. Superior mesenteric ganglion Postganglionic fibers leave the: - superior mesenteric ganglion and distribute in perivascular plexuses that follow the branches of the celiac trunk to reach their target viscera 43 SMU - Internal Data Describe the parasympathetic innervation of the midgut structures of the abdomen. Esophagus Preganglionic parasympathetic innervation to midgut structures originate from: -Vagus nerve (CN X); cell bodies are located in the brain stem From here the preganglionic fibers synapse with postganglionic neurons in terminal ganglia located on the surface of the organs or within the walls of midgut viscera. Note: Preganglionic fibers pass through superior mesenteric ganglion without synapsing Anterior vagal trunk (from vagus nerve) Superior mesenteric ganglion Postganglionic fibers then: -contribute to the abdominal autonomic plexuses to reach their target organ 44 SMU - Internal Data HINDGUT VISCERA WITH INFERIOR MESENTERIC ARTERY •Distal 1/3 of transverse colon •Descending colon •Sigmoid colon •Rectum •Superior 2/3 of anal canal •The pectinate line of the anal canal forms the inferior limit of the gut derived portion of the GI tract. The inferior 1/3 of the anal canal is somatically derived. 45 SMU - Internal Data Describe the functions, relationships, arterial supply, venous drainage of the transverse colon. Transverse Colon Functions: -storage and transport of feces Arterial supply: Middle colic artery (from superior mesenteric artery) Venous Drainage: Middle colic vein Middle colic artery -to transverse colon -right and left branches 46 SMU - Internal Data Describe the location of the inferior mesenteric artery and its main branches. Inferior mesenteric artery -supplies structures derived from the hindgut -Located at L3 vertebral level Branches include: 1) Left colic artery (to descending colon) 2) Sigmoidal arteries (approx. 4) 3) Superior rectal artery (to the rectum) 4) Marginal artery (of Drummond) • An anastomotic connection consisting of primary branches of the ileocolic, right colic, middle colic, left colic, and sigmoidal arteries. The marginal artery courses parallel to the large intestine. Celiac trunk (foregut) Superior Mesenteric Artery (midgut) Inferior Mesenteric Artery (hindgut) 47 SMU - Internal Data Marginal artery Left colic artery -to the descending colon Superior rectal artery -to rectum Sigmoidal arteries -to sigmoid colon 48 SMU - Internal Data Describe the functions, relationships, arterial supply, venous drainage, and descending /sigmoid colon. Descending Colon Functions: -storage and transport of feces Left colic artery Arterial supply: Left colic artery Venous Drainage: Left colic vein Descending Colon Sigmoid Colon Functions: -storage and transport of feces Arterial supply: Sigmoid arteries Venous Drainage: Sigmoidal veins Sigmoidal arteries -to sigmoid colon Sigmoid Colon 49 SMU - Internal Data Describe the sympathetic innervation of the hindgut structures of the abdomen. Preganglionic sympathetic nerves to hindgut structures originate from the: -L1 and L2 cord segments From here the preganglionic fibers enter the: -lumbar portion of the sympathetic trunk, but do not synapse. -fibers exit the trunk via splanchnic nerves, the lumbar splanchnics, to reach collateral ganglia -Lumbar splanchnic fibers synapse with postganglionic neurons in the collateral ganglia that are related to inferior mesenteric artery Lumbar splanchnic nerves Postganglionic fibers: - follow the inferior mesenteric artery to reach the hindgut. Other lumbar splanchnic fibers reach and synapse with postganglionic neurons in the collateral ganglia of the plexuses that are in the pelvic floor. These postganglionic fibers follow pelvic vessels and nerves to supply the pelvic viscera. 50 SMU - Internal Data Describe the parasympathetic innervation of the hindgut structures of the abdomen. Preganglionic parasympathetic innervation to hindgut structures originate from: -S2, S3 and 4 sacral spinal cord segments, ventral horn From here the preganglionic fibers leave the spinal nerves of those three segments as pelvic splanchnic nerves. These will ascend and synapse with postganglionic neurons in terminal ganglia located on the surface of the organs or within the walls of hindgut viscera. Pelvic splanchnic nerves 51 SMU - Internal Data 52 SMU - Internal Data MAJOR LYMPATHIC CHANNELS The Lymphatic System: -lymphatic channels collect surplus tissue fluid (a well as pathogens, foreign antigens, and cell debris) lost from vascular capillary beds during nutrient exchange processes and deliver it back to the venous system. The lymphatic system also transports fat from the intestines (chyle) and is an integral part of the immune system. The Right Lymphatic Duct: -receives lymph from the right side of the head and neck, the right upper limb and the right side of the thorax (and some superficial abdominal lymph) -usually drains directly into the right venous angle (junction of right subclavian and right internal jugular vv.) The Thoracic duct: - lymph from the rest of the body drains to the thoracic duct - begins in the abdomen (L2) at the Cisterna chyli (saccular dilation that receives lymph from the body below the diaphragm) - enters thorax through aortic hiatus of the diaphragm (T12) - ascends through the posterior mediastinum between aorta and azygos vein, posterior to the esophagus - Passes through the superior mediastinum and terminates at the left venous angle (junction of left subclavian and left internal jugular vv.) Lymphatic Trunks: -Trunks are responsible for collecting lymph from major regions of the body and draining it to the lymphatic ducts. -The paired bronchomediastinal trunks are the main lymphatic vessels of the thorax -Gut-derived structures inferior to the diaphragm drain to the unpaired Intestinal trunk -All remaining structures inferior to the diaphragm drain to the right and left lumbar trunks SMU - Internal Data 53 The Bronchomediastinal Trunks receive lymphatics from thoracic viscera and drain to the ducts. The Cisterna Chyli is at the origin of the thoracic duct. It is located on the bodies of L1 and L2 vertebrae between the aorta and right diaphragmatic crus. The cisterna Chyli receives lymph from: • Intestinal Trunk (1): which drains lymph from preaortic nodes that lie on the abdominal aorta surrounding the origins of the Celiac, SMA, IMA. • Right and Left Lumbar trunks: which drain lymph from para-aortic (a.k.a. lateral aortic or lumbar) nodes lying on either side of the abdominal aorta. 54 SMU - Internal Data REFERRED PAIN Visceral pain is often referred to (i.e. is perceived as coming from) the surface of the body. There are MANY pathways of referred pain. One pathway occurs because both visceral and somatic (primary) sensory neurons (in the DRG) synapse on common secondary sensory neurons (interneurons) in the dorsal horn of the spinal cord. The brain is unable to determine whether visceral or somatic afferents stimulated the secondary neurons and so perceives it as having come from both. Pain from certain organs is generally referred to specific areas of the body surface related to the dermatomes represented in the spinal segments where the visceral afferents terminate. The nine-region organizational system of the abdomen can not only be used to understand (and communicate about) the organization of abdominal contents, but it is also helpful for deducing the source of referred abdominal pain…. - foregut viscera tend to refer to the epigastric region of the abdomen - midgut viscera tend to refer to the umbilical region of the abdomen - hindgut viscera tend to refer to the pubic region of the abdomen 55 SMU - Internal Data REFERRED PAIN FROM THE ABDOMINAL VISCERA -THE NINE-REGION ORGANIZATIONAL SYSTEM- 56 SMU - Internal Data