l8 stomch dudenum and spleen

Gastrointestinal Tract - Anatomy Overview

Mouth, Pharynx, and Esophagus

• Esophagus:
  • Passes through the diaphragm at the T10 level.
  • Stratified squamous epithelium transitions to columnar epithelium in the lower esophagus (Squamocolumnar Junction).
  • Hiatal Hernia: Can alter the normal anatomy of this junction.

Stomach

• Location:
  • Situated in the left hypochondrium and epigastrium.
• Structure:
  • Four regions:
    1. Cardia: Entry of food.
    2. Fundus: Upper part.
    3. Body: Main central region.
    4. Pyloric region: Includes the antrum and canal leading to the pyloric sphincter.
• Muscle Layers:
  • Outer Longitudinal Layer.
  • Middle Circular Layer.
  • Innermost Oblique Layer: Unique to the stomach, aids in mechanical digestion.
• Lining:
  • Epithelium: Simple columnar epithelium.
  • Rugae: Folds that increase surface area.
• Sphincters:
  • Cardiac Sphincter: Controls food entry.
  • Pyloric Sphincter: Strong sphincter that controls food exit into the duodenum (L1 level).
• Functions:
  • Mechanical Digestion: Churning of food.
  • Chemical Digestion: Secretion of hydrochloric acid.
  • Converts food into "chyme."

Stomach Relations

• Anterior:
  • Abdominal wall, costal margin, diaphragm, and left lobe of the liver.
  • Anterior ulcers may perforate into these structures.
• Posterior:
  • Lesser sac, pancreas, splenic artery, spleen, left kidney, and adrenal gland.
  • Posterior ulcers may lead to lesser sac abscesses or erosion into nearby structures (e.g., pancreas, splenic artery).

Omenta and Ligaments

• Greater Omentum:
  • Large fatty layer attached to the greater curvature.
  • Contains greater sac and forms the lesser sac behind the stomach.
• Lesser Omentum:
  • Attaches to the lesser curvature.
  • Contains the hepatogastric ligament and hepatoduodenal ligament.
  • Lesser Sac: Space behind the stomach formed due to the stomach's 90-degree rotation during development.

Blood Supply

• Arterial Supply:
  • Foregut (Stomach to D2 of the duodenum): Supplied by the celiac trunk (T12).
    • Left Gastric Artery: Supplies the upper lesser curvature.
    • Common Hepatic Artery:
      • Right Gastric Artery: Supplies the lower lesser curvature.
      • Gastroduodenal Artery: Gives rise to the right gastroepiploic artery.
    • Splenic Artery:
      • Supplies the fundus via short gastric arteries and the upper greater curvature via the left gastroepiploic artery.
• Venous Drainage:
  • Lesser curvature veins drain into the portal vein.
  • Greater curvature veins drain into the splenic vein and superior mesenteric vein (SMV).

Lymphatic Drainage

• Gastric Lymphatics:
  • Drain along the arteries to the celiac lymph nodes.
  • Involves perigastric nodes and suprapancreatic nodes.

Nerve Supply

• Autonomic Nervous System:
  • Sympathetic: Through the celiac plexus at T12-L1 via thoracic splanchnic nerves.
  • Parasympathetic: From the vagal trunks (anterior and posterior).
  • Nerves of Latarjet: Run along the lesser curvature.

Duodenum

• Length: 10 inches (25 cm) and divided into four parts:
  1. D1 (Superior Part): 2 inches long, at L1.
     • Common site for peptic ulcers.
  2. D2 (Descending Part): 3 inches long, at L2.
     • Receives bile and pancreatic ducts.
  3. D3 (Horizontal Part): 4 inches long, at L3.
     • Crosses anterior to the aorta and IVC.
  4. D4 (Ascending Part): 1 inch long, at L2.
     • Terminates at the duodenojejunal flexure.
• Blood Supply:
  • Proximal to Major Duodenal Papilla:
    • Celiac Trunk via gastroduodenal artery.
  • Distal to Major Duodenal Papilla:
    • Superior Mesenteric Artery (SMA) via inferior pancreaticoduodenal artery.
• Venous Drainage: Veins parallel the arteries, draining into the portal venous system.

Spleen

• Location: Left hypochondrium, deep to ribs 9-11.
• Size: 1x3x5 inches, weighing 7 ounces.
• Function: Filters blood, removing old erythrocytes.
• Blood Supply:
  • Splenic Artery: Branch of the celiac trunk, runs along the tail of the pancreas within the splenorenal ligament.
• Relations:
  • Gastrosplenic Ligament: Contains short gastric and left gastroepiploic arteries.
  • Splenorenal Ligament: Contains splenic artery and vein.

Clinical Points

• Peptic Ulcer Disease:
  • Stomach Ulcers: Present with epigastric pain worsened by eating.
  • Duodenal Ulcers: Present with epigastric pain eased by eating.
• Hiatal Hernia: Can cause the squamocolumnar junction to move, potentially leading to gastroesophageal reflux.
• Portal Hypertension: May result in esophageal varices due to swollen submucosal veins.

Esophagus

• Passes through the diaphragm at the T10 level.
• Transitions from stratified squamous epithelium to columnar epithelium at the Squamocolumnar Junction.
• Hiatal Hernia can disrupt the normal anatomy of this junction.

Stomach

• Located in the left hypochondrium and epigastrium.
• Composed of four regions:
  • Cardia: Food entry point.
  • Fundus: Upper section.
  • Body: Central area.
  • Pyloric region: Includes antrum and canal leading to pyloric sphincter.
• Muscle Layers:
  • Outer Longitudinal Layer, Middle Circular Layer, and Innermost Oblique Layer unique to the stomach, aiding in mechanical digestion.
• Lined with simple columnar epithelium; features rugae (folds) that enhance surface area.

Sphincters

• Cardiac Sphincter: Regulates food entry into the stomach.
• Pyloric Sphincter: Strong sphincter controlling food exit into the duodenum at L1 level.

Functions of the Stomach

• Mechanical digestion through churning.
• Chemical digestion via hydrochloric acid secretion, converting food into chyme.

Stomach Relations

• Anterior: Related to the abdominal wall, diaphragm, and left lobe of the liver; anterior ulcers can lead to perforations.
• Posterior: Associated with the lesser sac, pancreas, spleen, left kidney, and adrenal gland; posterior ulcers can create abscesses or erosions.

Omenta and Ligaments

• Greater Omentum: Fatty layer attached to the greater curvature, containing the greater and lesser sacs.
• Lesser Omentum: Attaches to the lesser curvature with hepatogastric and hepatoduodenal ligaments.
• Lesser Sac: Space behind the stomach formed by its developmental rotation.

Blood Supply

• Foregut is supplied by the celiac trunk (T12).
• Key arteries:
  • Left Gastric Artery: Supplies upper lesser curvature.
  • Common Hepatic Artery: Supplies lower lesser curvature through Right Gastric and Gastroduodenal artery.
  • Splenic Artery: Supplies the fundus via short gastric arteries.
• Venous Drainage:
  • Lesser curvature veins drain into the portal vein.
  • Greater curvature veins drain into splenic and superior mesenteric veins.

Lymphatic Drainage

• Drains along the arteries to celiac lymph nodes, including perigastric and suprapancreatic nodes.

Nerve Supply

• Sympathetic: Via celiac plexus at T12-L1 through thoracic splanchnic nerves.
• Parasympathetic: From vagal trunks (anterior and posterior); Nerves of Latarjet run along the lesser curvature.

Duodenum

• Length: 10 inches (25 cm) divided into four parts:
  • D1 (Superior Part): 2 inches, located at L1, common site for peptic ulcers.
  • D2 (Descending Part): 3 inches at L2, receives bile and pancreatic ducts.
  • D3 (Horizontal Part): 4 inches at L3, crosses anterior to aorta and IVC.
  • D4 (Ascending Part): 1 inch at L2, terminates at duodenojejunal flexure.
• Blood Supply:
  • Proximal to Major Duodenal Papilla: Celiac Trunk via gastroduodenal artery.
  • Distal to Major Duodenal Papilla: Superior Mesenteric Artery via inferior pancreaticoduodenal artery.

Spleen

• Location: Left hypochondrium, beneath ribs 9-11.
• Size: Approximately 1x3x5 inches, weighing around 7 ounces.
• Function: Filters blood, removing old erythrocytes.

Blood Supply to Spleen

• Supplied by Splenic Artery, a branch of the celiac trunk, running along the pancreas' tail.

Relations of Spleen

• Gastrosplenic Ligament: Contains short gastric and left gastroepiploic arteries.
• Splenorenal Ligament: Contains the splenic artery and vein.

Clinical Points

• Peptic Ulcer Disease:
  • Stomach ulcers: Cause epigastric pain worsened by eating.
  • Duodenal ulcers: Cause epigastric pain eased by eating.
• Hiatal Hernia: Can move squamocolumnar junction, leading to gastroesophageal reflux.
• Portal Hypertension: May result in esophageal varices due to swollen submucosal veins.

Test your knowledge on the anatomy of the stomach and spleen, including their blood supply, lymphatics, and peritoneal attachments. This quiz will cover key learning outcomes from the GIHEP course at the Royal College of Surgeons in Ireland. Ideal for students preparing for their assessments under Dr. Ciara Murphy.