# Lecture 8: Stomach and Spleen ## Unit 1.4: Human Gross Anatomy II - Thorax and Abdomen --- ## Learning Objectives By the end of this lecture, students will be able to: 1. Describe the gross anatomy of the stomach including its parts, surfaces, and curvatures 2. Identify the anatomical relationships of the stomach 3. Describe the blood supply, venous drainage, and lymphatic drainage of the stomach 4. Explain the gross anatomy and function of the spleen 5. Describe the blood supply of the spleen and its clinical significance 6. Correlate anatomical knowledge with common gastric and splenic pathologies --- ## Overview of the Stomach The stomach is the most dilated part of the gastrointestinal tract, serving as a reservoir for ingested food, a mixing chamber where food is mechanically broken down and mixed with gastric secretions, and the site of initial protein digestion. It is continuous with the esophagus above and the duodenum below. The stomach occupies the left upper quadrant and epigastric region of the abdomen, extending from approximately T11 vertebral level to L1-L2. Its size and position vary considerably depending on the volume of its contents and the position of the body, as the stomach is a mobile, intraperitoneal organ. The capacity of the stomach changes dramatically with filling. When empty, the stomach holds approximately 50 milliliters and the mucosa is thrown into prominent folds called rugae. A comfortable meal fills the stomach to about 1 liter. The maximum capacity can reach 4 liters with distension. Panel A: The stomach positioned in the left upper quadrant and epigastric region, extending from approximately T11 to L1-L2 vertebral levels. Panel B: Anatomical relationships showing the diaphragm superiorly, liver to the right, and spleen to the left of the stomach. Panel C: The esophageal entry superiorly and duodenal exit to the right, demonstrating the stomach's position in the GI tract. Panel D: Cross-sectional inset of the empty stomach showing prominent mucosal rugae that flatten with distension, with surface landmarks and 5 cm scale bar. --- ## Parts of the Stomach The stomach is divided into four regions based on anatomical and functional characteristics. The cardia is the small region immediately surrounding the esophageal opening at approximately the T11 vertebral level. This is where the esophagus transitions into the stomach. Although there is no true anatomical sphincter here, the lower esophageal sphincter provides a functional barrier to prevent reflux. The cardiac notch or incisura marks the acute angle between the esophagus and the fundus. The fundus is the dome-shaped portion of the stomach that rises above the level of the esophageal opening. It typically lies beneath the left dome of the diaphragm and contains gas that is visible as an air bubble on upright chest or abdominal radiographs. This gas bubble serves as a useful radiological landmark. The body or corpus of the stomach is the largest portion, extending from the fundus to the pyloric region. It is the main secretory area, containing the gastric glands that produce hydrochloric acid and pepsinogen. The body lies between the cardiac region and the angular notch on the lesser curvature. The pyloric region connects the body to the duodenum and is subdivided into three parts. The pyloric antrum is the wider, proximal portion where the smooth muscle wall begins to thicken. The pyloric canal is the narrow, 2-3 centimeter channel leading to the pylorus. The pylorus itself is the sphincter at the gastroduodenal junction, formed by a thick ring of circular smooth muscle that controls gastric emptying. The pylorus lies at the level of the L1 vertebra, which corresponds to the transpyloric plane. Panel A: The cardia surrounding the esophageal opening at T11 with the cardiac notch marking the acute angle between esophagus and fundus. Panel B: The dome-shaped fundus rising above the cardia, containing a gas bubble visible on radiographs as a useful landmark. Panel C: The body as the largest secretory portion extending to the angular incisure, with internal rugae visible. Panel D: The pyloric region subdivided into antrum, canal (2-3 cm), and pylorus with its thick sphincter at the L1 transpyloric plane, with vertebral levels and 4 cm scale bar. --- ## Curvatures and Surfaces The stomach has two curvatures and two surfaces. The lesser curvature forms the shorter, concave right border of the stomach. It is continuous with the right side of the esophagus superiorly. The angular incisure or angular notch is a distinct indentation on the lesser curvature that marks the junction between the body and pyloric antrum. The lesser omentum attaches along the entire length of the lesser curvature, connecting the stomach to the liver. The greater curvature forms the longer, convex left border of the stomach. It begins at the cardiac notch, arches over the fundus, and continues along the left side of the body and pyloric region to end at the pylorus. The greater omentum attaches to the greater curvature below the level of the fundus. The gastrosplenic ligament connects the upper greater curvature to the spleen. The anterior surface of the stomach faces anteriorly and superiorly. It contacts the left dome of the diaphragm superiorly, the left lobe of the liver to the right, and the anterior abdominal wall in the epigastric region. The posterior surface faces posteriorly and inferiorly, forming the anterior wall of the lesser sac. The structures in contact with the posterior surface of the stomach collectively form the stomach bed and include the pancreas, left kidney, left suprarenal gland, spleen, splenic artery, and transverse mesocolon. The lesser sac separates the posterior gastric surface from most of these structures. Panel A: The lesser curvature as the concave right border with the angular incisure marking the body-antrum junction and lesser omentum attachment. Panel B: The greater curvature as the convex left border from cardiac notch over the fundus, with greater omentum and gastrosplenic ligament attachments. Panel C: Anterior surface relations including diaphragm, left lobe of liver, and anterior abdominal wall in the epigastric region. Panel D: Posterior view showing the stomach bed - pancreas, left kidney, suprarenal gland, spleen, and splenic artery separated from the stomach by the lesser sac, with 4 cm scale bars. --- ## Anatomical Relationships The stomach has important relationships with surrounding structures that have clinical significance. Anteriorly, the stomach relates to the diaphragm, specifically the left dome, which separates it from the left lung, pleura, and pericardium. The left lobe of the liver covers the upper right portion of the stomach. In the epigastric region, the stomach contacts the anterior abdominal wall directly, explaining why epigastric pain is a common symptom of gastric pathology. Posteriorly, the stomach bed consists of structures that would be exposed if the stomach were lifted forward. The body of the pancreas lies directly behind the stomach. The left kidney occupies the upper pole position posterior and lateral. The left suprarenal gland sits superiorly. The spleen lies laterally, connected by the gastrosplenic ligament. The splenic artery courses along the upper border of the pancreas behind the stomach. The transverse colon and transverse mesocolon lie inferiorly, forming the lower part of the stomach bed. The left crus of the diaphragm lies superiorly. These structures are separated from the stomach by the lesser sac, which allows the stomach to move freely during filling and peristalsis. Panel A: Anterior gastric relations showing the diaphragm superiorly and left lobe of liver covering the upper right portion of the stomach. Panel B: The anterior abdominal wall in direct contact with the stomach in the epigastric region, explaining epigastric pain in gastric pathology. Panel C: The stomach lifted to reveal the stomach bed including pancreas body, left kidney, suprarenal gland, and spleen. Panel D: Complete view of posterior relations with splenic artery, transverse colon, transverse mesocolon, and lesser sac space separating the stomach from its bed, with 5 cm scale bars. --- ## Blood Supply of the Stomach The stomach has a rich arterial supply derived entirely from the celiac trunk, with vessels arranged along both curvatures. This extensive blood supply explains why gastric ulcers can cause significant hemorrhage but also why the stomach heals well and is relatively resistant to ischemia. Along the lesser curvature, two arteries form an anastomotic arcade. The left gastric artery arises directly from the celiac trunk and is the largest of the gastric vessels. It courses to the left along the lesser curvature, giving off an esophageal branch to the lower esophagus before continuing along the stomach. The right gastric artery arises from the hepatic artery proper and runs to the left along the lesser curvature to anastomose with the left gastric artery. Along the greater curvature, two gastroepiploic (or gastro-omental) arteries form a similar arcade. The left gastroepiploic artery is a branch of the splenic artery and runs along the left portion of the greater curvature within the greater omentum. The right gastroepiploic artery arises from the gastroduodenal artery (a branch of the common hepatic artery) and runs along the right portion of the greater curvature, anastomosing with the left gastroepiploic artery. The fundus receives additional supply from 4-5 short gastric arteries that arise from the splenic artery and pass through the gastrosplenic ligament to reach the gastric fundus. Venous drainage of the stomach parallels the arterial supply, with veins draining to the portal venous system. The left and right gastric veins drain directly into the portal vein. The short gastric veins and left gastroepiploic vein drain into the splenic vein. The right gastroepiploic vein drains into the superior mesenteric vein. At the lower esophagus, an important portosystemic anastomosis exists between the left gastric vein (portal drainage) and the esophageal veins that drain to the azygos system (systemic drainage). In portal hypertension, this anastomosis can become dilated, forming esophageal varices that may rupture and cause life-threatening hemorrhage. Panel A: The celiac trunk origin and its three branches - left gastric, common hepatic, and splenic arteries supplying the entire stomach. Panel B: The lesser curvature arterial arcade formed by anastomosing left and right gastric arteries from celiac trunk and hepatic artery respectively. Panel C: The greater curvature arcade from left and right gastroepiploic arteries, plus short gastric arteries to the fundus through the gastrosplenic ligament. Panel D: Venous drainage paralleling arteries to the portal system, with inset showing the portosystemic anastomosis at the lower esophagus between left gastric and azygos veins, with 4 cm scale bar. --- ## Lymphatic Drainage of the Stomach The lymphatic drainage of the stomach is clinically important because gastric cancer spreads along lymphatic pathways. The stomach is divided into four drainage zones, each with corresponding lymph node groups. The upper portion of the lesser curvature drains to the left gastric (or superior gastric) nodes along the left gastric artery. These nodes then drain to the celiac nodes. The lower portion of the lesser curvature drains to the right gastric and pyloric nodes, which then drain to the hepatic nodes along the hepatic artery before reaching the celiac nodes. The left portion of the greater curvature drains to the pancreaticosplenic nodes along the splenic artery, which then drain directly to the celiac nodes. The right portion of the greater curvature drains to the right gastroepiploic nodes along the gastroepiploic vessels, then to the pyloric nodes, and finally to the celiac nodes. All lymphatic drainage from the stomach ultimately reaches the celiac nodes, which represent the final common pathway before lymph enters the thoracic duct. This pattern of drainage explains why surgical treatment of gastric cancer often involves extensive lymph node dissection. Panel A: Upper lesser curvature zone draining to left gastric nodes along the left gastric artery toward the celiac nodes. Panel B: Lower lesser curvature zone draining to right gastric and pyloric nodes, then to hepatic nodes before reaching celiac nodes. Panel C: Left greater curvature zone draining to pancreaticosplenic nodes along the splenic artery directly to celiac nodes. Panel D: Right greater curvature zone draining to right gastroepiploic and pyloric nodes, with all pathways converging on the celiac nodes as the final common drainage, with 4 cm scale bar. --- ## Nerve Supply of the Stomach The stomach receives both parasympathetic and sympathetic innervation, which have opposing effects on gastric function. Parasympathetic innervation comes from the vagus nerves, which reach the stomach as the anterior and posterior vagal trunks formed from the esophageal plexus. The anterior vagal trunk, derived primarily from the left vagus, gives off anterior gastric branches to the anterior gastric surface. The posterior vagal trunk, derived primarily from the right vagus, gives off posterior gastric branches to the posterior surface and also sends celiac branches to the celiac plexus for distribution to other abdominal viscera. Parasympathetic stimulation increases gastric secretion, increases gastric motility, and relaxes the pyloric sphincter to promote gastric emptying. Sympathetic innervation reaches the stomach through the celiac plexus, which receives preganglionic fibers from the greater splanchnic nerve (T6-T9). Postganglionic sympathetic fibers travel with the gastric arteries to reach the stomach. Sympathetic stimulation decreases gastric secretion, decreases gastric motility, and contracts the pyloric sphincter to inhibit gastric emptying. The sympathetic fibers also carry pain sensation from the stomach. Vagotomy, surgical division of the vagus nerves, was historically performed as treatment for peptic ulcer disease to reduce gastric acid secretion. Various procedures ranged from truncal vagotomy (dividing the main vagal trunks) to highly selective vagotomy (dividing only the branches to the acid-secreting portion of the stomach). Complications of vagotomy include dumping syndrome from rapid gastric emptying and delayed gastric emptying from loss of the pyloric relaxation that normally accompanies gastric contractions. Panel A: The anterior vagal trunk descending from the esophagus and giving anterior gastric branches to the anterior stomach wall and hepatic branches to the liver. Panel B: The posterior vagal trunk providing posterior gastric branches and celiac branches that distribute with arteries to reach abdominal viscera. Panel C: Sympathetic innervation from the celiac plexus via the greater splanchnic nerve, with postganglionic fibers traveling along gastric arteries. Panel D: Summary table showing parasympathetic effects (increased secretion and motility, pyloric relaxation) versus sympathetic effects (decreased secretion and motility, pyloric contraction), with 4 cm scale bar. --- ## The Spleen The spleen is the largest lymphoid organ in the body, serving important functions in blood filtration and immune surveillance. It lies in the left upper quadrant of the abdomen in a posterolateral position, protected by the lower ribs. The spleen performs several essential functions. It filters blood, removing old, damaged, or abnormal red blood cells and recycling their iron content. It plays a central role in immune function, particularly in B lymphocyte activation and antibody production. The spleen is especially important for defense against encapsulated bacteria. It serves as a storage site for platelets, holding approximately 30% of the body's platelet pool, and as a reservoir for blood that can be mobilized during hemorrhage. During fetal life, the spleen is a site of hematopoiesis, and this function can resume in adults with bone marrow failure. The size of the spleen is clinically important. Normal dimensions are approximately 12 cm in length, 7 cm in width, and 3-4 cm in thickness, with a weight of 150-200 grams. A helpful memory aid is the "1-3-5-7-9-11 rule": the spleen measures 1 × 3 × 5 inches, weighs 7 ounces, and lies between ribs 9-11. Panel A: The spleen positioned in the left upper quadrant, protected by ribs 9, 10, and 11 in a posterolateral position. Panel B: Splenic relationships with diaphragm superiorly, stomach medially, left kidney posteromedially, and splenic flexure of colon inferiorly. Panel C: Normal splenic dimensions - approximately 12 cm length, 7 cm width, and 3-4 cm thickness, weighing 150-200 grams. Panel D: The "1-3-5-7-9-11" memory aid showing 1x3x5 inches, 7 ounces weight, lying between ribs 9-11, with 5 cm scale bar. --- ## Gross Anatomy of the Spleen The spleen has two main surfaces. The diaphragmatic surface is smooth and convex, lying against the left hemidiaphragm. The visceral surface is irregular and contains impressions from adjacent organs as well as the hilum. The visceral surface has several named impressions. The gastric impression, the largest, faces anteromedially toward the stomach. The renal impression on the posteromedial aspect contacts the left kidney. The colic impression on the anteroinferior aspect touches the splenic flexure of the colon. The pancreatic impression lies at the hilum where the tail of the pancreas approaches. The borders of the spleen are clinically important. The superior border is characteristically notched, with one or more palpable notches that can help identify an enlarged spleen on physical examination. The inferior border is rounded and less distinct. The hilum is located on the visceral surface and serves as the entry and exit point for the splenic vessels. The tail of the pancreas extends to this point within the splenorenal ligament. The spleen has anterior (or inferior) and posterior (or superior) poles. The anterior pole points toward the splenic flexure of the colon, while the posterior pole points toward the vertebral column. Panel A: The smooth convex diaphragmatic surface conforming to the left hemidiaphragm with characteristic notches on the superior border. Panel B: The visceral surface with gastric impression (largest, anteromedial) and renal impression (posteromedial) from adjacent organs. Panel C: The colic impression (anteroinferior) from the splenic flexure and pancreatic impression at the hilum where the pancreatic tail approaches. Panel D: The hilum as a longitudinal fissure for vessel entry, with anterior and posterior poles labeled and 3 cm scale bar indicating 12 cm total length. --- ## Peritoneal Relations and Ligaments The spleen is an intraperitoneal organ, almost entirely covered by visceral peritoneum except at the hilum where vessels enter. It is connected to adjacent structures by two peritoneal ligaments. The gastrosplenic ligament connects the greater curvature of the stomach to the splenic hilum. This double layer of peritoneum transmits the short gastric vessels and the left gastroepiploic vessels from the splenic artery to the stomach. The splenorenal ligament, also called the lienorenal ligament, connects the spleen to the left kidney. This double layer of peritoneum transmits the splenic artery and vein as well as the tail of the pancreas, which extends nearly to the splenic hilum. These ligaments define the left boundary of the lesser sac. The gastrosplenic ligament forms the anterior layer, while the splenorenal ligament forms the posterior layer. The splenic vessels travel in the splenorenal ligament behind the stomach to reach the hilum. Panel A: The gastrosplenic ligament as a double peritoneal layer extending from the stomach's greater curvature to the splenic hilum. Panel B: Contents of the gastrosplenic ligament including short gastric vessels and left gastroepiploic vessels supplying the gastric fundus. Panel C: The splenorenal ligament extending from the spleen to the left kidney, containing the splenic artery, splenic vein, and tail of the pancreas. Panel D: Transverse section showing how these ligaments define the left boundary of the lesser sac, with the potential space between stomach and splenorenal ligament and 3 cm scale bar. --- ## Blood Supply of the Spleen The splenic artery is the largest branch of the celiac trunk and follows a characteristic tortuous course along the superior border of the pancreas. Its serpentine path accommodates the changes in position of the spleen during respiration and postural changes. Along its course, the splenic artery gives off multiple branches to the pancreas. At the splenic hilum, the splenic artery divides into several segmental branches, typically a superior and inferior terminal branch, which further divide into trabecular arteries entering the splenic parenchyma. Importantly, the splenic artery is an end artery within the spleen, meaning there are no anastomoses between branches within the splenic tissue. Occlusion of a branch therefore causes segmental infarction. The splenic vein forms at the hilum from the union of segmental veins draining the spleen. It courses to the right behind the body and tail of the pancreas, receiving the inferior mesenteric vein along its course. At the neck of the pancreas, the splenic vein joins the superior mesenteric vein to form the portal vein. Splenic vein thrombosis, which can occur as a complication of pancreatitis, causes isolated left-sided portal hypertension with development of gastric varices through the short gastric veins, while the rest of the portal system remains unaffected. Panel A: The splenic artery arising from the celiac trunk and following a characteristic tortuous course along the superior border of the pancreas. Panel B: Pancreatic branches from the splenic artery and terminal division into superior and inferior segmental branches at the splenic hilum. Panel C: The splenic vein forming at the hilum, coursing behind the pancreas, and receiving the inferior mesenteric vein before joining the SMV to form the portal vein. Panel D: Inset cross-section of the spleen showing the end-artery pattern with distinct segmental territories that infarct separately if occluded, with 4 cm scale bar. --- ## Clinical Correlations Understanding the anatomy of the stomach and spleen is essential for recognizing and managing several important clinical conditions. Gastric ulcer typically occurs on the lesser curvature, particularly on the posterior wall. A posterior ulcer may erode into the left gastric artery, causing significant hemorrhage, or penetrate posteriorly into the pancreas, causing pain that radiates to the back and potentially leading to pancreatitis. The rich blood supply of the stomach makes gastric ulcer bleeding a common cause of upper gastrointestinal hemorrhage. Splenomegaly, or enlargement of the spleen, causes the organ to extend below the left costal margin where it becomes palpable on abdominal examination. The characteristic notched superior border helps distinguish an enlarged spleen from other left upper quadrant masses such as an enlarged kidney. Common causes of splenomegaly include portal hypertension from liver disease, infectious mononucleosis and other infections, and hematologic malignancies such as lymphoma and leukemia. Splenic rupture is a surgical emergency, typically resulting from blunt abdominal trauma such as motor vehicle accidents, falls, or contact sports injuries. The spleen's subcapsular location beneath the ribs provides some protection, but the organ's soft, blood-filled parenchyma is vulnerable to injury. Kehr's sign, left shoulder pain occurring with splenic injury, results from blood irritating the left hemidiaphragm and referred pain through the phrenic nerve (C3-5 shoulder dermatomes). Splenic rupture may present immediately or may be delayed if a subcapsular hematoma initially contains the hemorrhage before rupturing. Following splenectomy, patients are at increased risk for overwhelming post-splenectomy infection, particularly from encapsulated bacteria such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Vaccination against these organisms is essential before or immediately after splenectomy. Accessory spleens, small nodules of splenic tissue found in 10-30% of people, are typically located near the splenic hilum or in the gastrosplenic ligament. If splenectomy is performed for hematologic disease, accessory spleens must be identified and removed to prevent recurrence. Panel A: Gastric ulcer on the posterior lesser curvature with potential erosion into the left gastric artery causing hemorrhage or penetration into the pancreas causing back pain. Panel B: Splenomegaly examination showing the enlarged spleen palpable below the left costal margin with its characteristic notched border helping distinguish it from other masses. Panel C: Splenic rupture from blunt trauma with laceration, intraperitoneal hemorrhage, and Kehr's sign (referred left shoulder pain from diaphragmatic irritation). Panel D: Accessory spleens as small nodules near the hilum or in the gastrosplenic ligament, important to identify during splenectomy for hematologic disease, with 3-4 cm scale bars. --- ## Summary The stomach is divided into four parts: cardia, fundus, body, and pyloric region (antrum, canal, and pylorus). The lesser curvature with its angular incisure lies on the right, while the convex greater curvature lies on the left. Blood supply derives entirely from the celiac trunk, with left and right gastric arteries along the lesser curvature, left and right gastroepiploic arteries along the greater curvature, and short gastric arteries to the fundus. Venous drainage follows the arterial pattern to the portal system, with an important portosystemic anastomosis at the lower esophagus that can form varices in portal hypertension. Lymphatic drainage divides the stomach into four zones, all ultimately draining to the celiac nodes. The spleen is the largest lymphoid organ, functioning in blood filtration, immune response, platelet storage, and serving as a blood reservoir. It is connected by the gastrosplenic ligament (containing short gastric vessels) and splenorenal ligament (containing splenic vessels and pancreatic tail). The splenic artery is an end artery, making segmental infarction possible with branch occlusion. Splenic rupture from trauma is a surgical emergency, characteristically causing left shoulder pain (Kehr's sign) from diaphragmatic irritation. Post-splenectomy patients require vaccination against encapsulated organisms due to their increased infection risk. --- ## Key Terms | Term | Definition | |------|------------| | Angular incisure | Notch on the lesser curvature marking the junction between the body and pyloric antrum | | Stomach bed | Posterior relations of the stomach including the pancreas, left kidney, suprarenal gland, and spleen | | Celiac trunk | Origin of all gastric arteries; gives rise to left gastric, common hepatic, and splenic arteries | | Splenorenal ligament | Peritoneal fold connecting the spleen to the left kidney; contains splenic vessels and pancreatic tail | | Kehr's sign | Left shoulder pain from diaphragmatic irritation, classically seen in splenic rupture | | Gastrosplenic ligament | Peritoneal fold connecting the stomach to the spleen; contains short gastric and left gastroepiploic vessels | --- *This content is subject to the [MIT License](https://opensource.org/licenses/MIT). © 2024–2026 Hibbert School of Medicine.*