Stomach & Pancreas Lecture 5 PDF

Stomach Learning Objectives: Functions of stomach Gross anatomy – Location, shape, size and capacity – External features – ends, openings, curvatures, surfaces – Parts – Relations – Interior – Blood supply, nerve supply, lymphatic drainage Developmental and applied anatomy Functions of stomach Speci...

Stomach Learning Objectives: Functions of stomach Gross anatomy – Location, shape, size and capacity – External features – ends, openings, curvatures, surfaces – Parts – Relations – Interior – Blood supply, nerve supply, lymphatic drainage Developmental and applied anatomy Functions of stomach Specialized for the accumulation of ingested food, which it chemically and mechanically prepares for digestion and passage into the duodenum. The stomach acts as a food blender and reservoir; its chief function is enzymatic digestion. The gastric juice gradually converts a mass of food into a semiliquid mixture, chyme, which passes fairly quickly into the duodenum The functions of the stomach include - storage of food, digestion, mixing of food into chyme, acid secretion, enzyme secretion, hormone secretion, absorption, periodic release of chyme into the duodenum which is the first part of the small intestine Stomach – gross anatomy Most dilated part of GIT between the esophagus and small intestine Located in the upper left part of abdomen - left hypochondriac, epigastric and umbilical regions of abdomen 10 inches long Having a capacity of 30 ml in the new born and 1½ to 2 liters in adults When empty it looks ‘J’ shaped External features of stomach: Ends: cardiac and pyloric ends Orifices: cardiac and pyloric orifices Curvatures: lesser and greater Surfaces: anterior and posterior Cardiac end: is the upper end Esophagus continuous with the stomach Located at the level of T11 vertebra Presents cardiac orifice Pyloric end: is the lower end Stomach continues as duodenum Located at the level of L1 vertebra Presents pyloric sphincter (pylorus) which has pyloric orifice Cardiac end Pyloric end Duodenum Lesser curvature (right border): Concave, shorter than the greater curvature Presents angular notch (incisura angularis) Gives attachment to lesser omentum Related to right and left gastric vessels Greater curvature (left border): Convex, longer than the lesser curvature Gives attachment to greater omentum, gastrosplenic and gastrophrenic ligaments Related to right and left gastroepiploic vessels Lesser curvature Lesser omentum Greater omentum GastroSplenic ligament Greater curvature Coeliac trunk Hepatic artery Left gastric artery Right gastric artery Right gastroepoploic artery Splenic artery Left gastroepoploic artery Greater omentum Parts of stomach: 4 parts Cardia Fundus Body Pyloric part which has pyloric antrum and pyloric canal Cardia: part surrounding the cardiac orifice Fundus: Dome shaped part, situated above the level of cardiac orifice Contains undigested food and filled with gas Body: Largest part lies between fundus and pyloric antrum Pyloric antrum: Situated between body and pyloric canal Pyloric canal: Narrow, tubular part At its right end presents pyloric sphincter (pylorus) which guards pyloric orifice Relations of stomach: Anterior surface: related to Anterior abdominal wall, diaphragm, left lobe of liver, left costal margin, left lung and left pleura Liver (left lobe) Left costal margin Diaphragm Posterior surface: related to Lesser sac, diaphragm, left kidney, left suprarenal gland, splenic artery, splenic flexure of colon, pancreas, and transverse mesocolon Spleen Splenic artery Stomach (cut) Spleen Transverse mesocolon Stomach (cut) Pancreas Left kidney Splenic Flexure of colon Interior of stomach Interior of stomach shows gastric rugae and gastric pits Gastric rugae: Folds of mucous membrane Disappear when the stomach is distended Gastric pits: Depressions which open into the lumen of stomach Each receives openings of 2 to 3 gastric glands Gastric canal: is a groove formed temporarily by the gastric rugae along the lesser curvature during swallowing Saliva, small quantities of masticated food and other fluids drain along the gastric canal to the pyloric canal when the stomach is mostly empty Pyloric orifice Gastric rugae Arterial supply: (branches of coeliac trunk) Left gastric artery (splenic) Coeliac trunk Hepatic artery Short gastric artery Right gastric artery (hepatic) Left gastroepoploic artery (splenic) Right gastroepoploic artery (gastroduodenal) Splenic artery Greater omentum Venous drainage of stomach Veins of stomach drain into superior mesenteric, splenic and portal veins Nerve supply: Parasympathetic nerves – anterior and posterior vagal trunks Sympathetic nerves – arise from T6 to T9 spinal segments and distributed via coeliac plexus, hepatic plexus and greater splanchnic nerves Lymphatic drainage: Lymph drains to right gastric, left gastric, right gastroepiploic, left gastroepiploic, short gastric nodes Left gastroepiploic and short gastric nodes drain into pancreaticosplenic nodes Lymph from right gastric, left gastric, right gastroepiploic nodes drains to hepatic nodes Lymph from the pacreaticosplenic, hepatic nodes drains into coeliac nodes Development of stomach Appears as a fusiform dilation of the foregut in week 4 Has dorsal mesogastrium and ventral mesogastrium Rotates 90⁰ around its longitudinal axis - results in the left side facing anteriorly and its right side facing posteriorly Cranial and caudal ends originally lie in the midline Stomach rotates around an anteroposterior (a-p) axis caudal end moves to the right and upward, cranial end moves to the left and slightly downward Applied anatomy Gastric canal along lesser curvature is a common site for occurrence of peptic ulcer because – This area is irritated most by the swallowed liquids – More number of secretomotor supply from vagal trunks Gastric pain is referred to the epigastric region (due to the nerve supply from T6 to T9 spinal segments A hiatal (hiatus) hernia is a protrusion of part of the stomach into the thorax through the esophageal opening of the diaphragm Pylorospasm is characterized by failure of the smooth muscle fibers encircling the pyloric canal to relax normally. As a result, food does not pass easily from the stomach into the duodenum and the stomach becomes overly full, usually resulting in discomfort and vomiting A posterior gastric ulcer may erode through the stomach wall into the pancreas, resulting in referred pain to the back. In such cases, erosion of the splenic artery results in severe hemorrhage into the peritoneal cavity Pancreas Objectives Location, shape and size Features and relation of different parts Ducts of pancreas Blood supply Nerve supply Lymphatic drainage Applied anatomy Pancreas Elongated (about 6 inches long), accessory digestive gland, located horizontally on the posterior abdominal wall at the level of L1 and L2 vertebrae (transpyloric plane) ‘J’ shaped retroperitoneal organ, located behind the stomach and between the duodenum and spleen Has exocrine and endocrine parts Exocrine part – exocrine secretion (pancreatic juice from the acinar cells) enters duodenum through main and accessory pancreatic ducts Endocrine part – endocrine secretions (glucagon and insulin from the pancreatic islets of Langerhans) enter the blood Parts of pancreas Tail Head, neck, body and tail Head has uncinate process Body Neck Head Uncinate process Expanded part of the gland, surrounded by the C-shaped curve of the duodenum Firmly attaches to the descending (2nd) and horizontal (3rd) parts of the duodenum Lower part of head has a projection - uncinate process Relations of Head of Pancreas: Posterior: Inferior vena cava, right renal artery and vein, left renal vein, bile duct (forms a grove on the posterior surface) Anterior: transverse colon Relations of uncinated process: Located posterior to the superior mesenteric artery and vein and anterior to abdominal aorta Located above the horizontal (2nd) part of duodenum Head of pancreas Pancreas Celiac trunk Upper border of body of pancreas Splenic artery Hepatic artery Spleen Duodenum 1st part Tail of pancreas Pyloric part of stomach Duodenum 2nd part Anterior border of body Head of pancreas Superior mesenteric artery and vein Duodenum 3rd part Uncinate process Posterior relations of head and body of pancreas Inferior vena cava Left suprarenal gland Left kidney Right renal vessels Left renal vessels Superior Mesenteric artery Abdominal aorta Neck of the pancreas Short constricted part between head and body Located behind the neck are - terminal parts of superior mesenteric and splenic veins and origin of portal vein Pylorus of stomach is located anterior to the neck Portal vein Superior mesenteric vein Splenic vein Body: Longest part, forms part of stomach bed Relations of body of pancreas: Anterior relations: Lesser sac, stomach Posterior relations: Abdominal aorta, origin of superior mesenteric artery, left kidney, left renal vessels, splenic vein Upper border: has Celiac artery and its 2 branches (hepatic and splenic arteries) Anterior border: Gives attachment to greater omentum and transverse mesocolon Blood vessels related to pancreas Arteries along the upper border of body of pancreas Celiac trunk Hepatic artery Splenic artery Upper border of body of pancreas Tail: Lies anterior to the left kidney, and it is closely related to the spleen The tail is relatively mobile and is located in the splenorenal (leinorenal) ligament with the splenic vessels Tail Pancreatic ducts Carry the secretions from the exocrine part to the second part of duodenum Two ducts - Main and accessory pancreatic ducts Usually, the accessory duct communicates with the main pancreatic duct Bile duct Accessory pancreatic duct Hepatopancreatic ampulla Main pancreatic duct Main pancreatic duct: Begins in the tail, enters wall of 2nd part of duodenum Joins bile duct to form hepatopancreatic ampulla which opens on major duodenal papilla 3 sphincters - sphincter of the pancreatic duct (around the terminal part of the pancreatic duct), the sphincter of the bile duct (around the termination of the bile duct), and the Accessory pancreatic duct: hepatopancreatic sphincter (of Oddi) Begins in the lower part of head - around the hepatopancreatic Terminates by opening on minor duodenal papilla in the 2nd part of ampulla duodenum Blood supply Arterial supply: Splenic artery Superior pancreaticoduodenal artery Inferior pancreaticoduodenal artery Venous drainage: Portal vein, splenic vein, superior mesenteric vein Nerve supply and lymphatic drainage Nerve supply: Supplied by vagus (parasympathetic) and splanchnic nerves (sympathetic) The parasympathetic fibers are secretomotor, but pancreatic secretion is primarily mediated by secretin and cholecystokinin hormones formed by the epithelial cells of the duodenum and proximal intestinal mucosa under the stimulus of acid contents from the stomach Lymphatic Drainage: Lymphatic vessels follow the blood vessels and end in the pancreaticosplenic and pyloric lymph nodes Efferent vessels from these nodes drain to the superior mesenteric lymph nodes or to the celiac lymph nodes (via the hepatic lymph nodes) Applied anatomy Blockage of Hepatopancreatic Ampulla and Pancreatitis Gallstone passing along the bile duct may lodge in the distal end of the hepatopancreatic ampulla resulting in obstruction of both the biliary and pancreatic duct systems Bile may back up and enter the pancreatic duct, usually resulting in pancreatitis (inflammation of the pancreas Pancreatic Cancer Cancer of the pancreatic head – compresses and obstructs bile duct and/or the hepatopancreatic ampulla Results in retention of bile pigments, enlargement of the gallbladder, and obstructive jaundice Cancer of the neck and body of the pancreas – obstruction of portal vein or inferior vena cava Applied anatomy Accessory Pancreatic Tissue Presence of pancreatic tissue in the stomach, duodenum, ileum, or an ileal diverticulum (may contain pancreatic islet cells that produce glucagon and insulin) Pancreatectomy For the treatment of chronic pancreatitis, most of the pancreas may be removed - pancreatectomy Rupture of Pancreas Pancreatic injury result from sudden, severe, forceful compression of the abdomen Rupture of the pancreas tears its duct system, pancreatic juice enters the parenchyma of the gland and adjacent tissues Digestion of pancreatic and other tissues by pancreatic juice is very painful