Lecture Notes: Anatomy of the Spleen

Practical Exams

• Organ identification
• Clinical questions on spleen injury
• Strategies to answer clinical questions
• Important aspects of practical exams

Introduction to Spleen

• Organ of mystery (Gallan)
• Appearance: Soft, purplish organ in the lymphatic system
• Surrounded by capsule: with smooth muscle cells (not in humans)
• Histological significance: Evolution of spleen

Position and Dimensions

• Abdominal quadrants: Left upper quadrant, under the diaphragm
• Rule of Odd Numbers:
  • 1 inch thick
  • 3 inches breadth
  • 5 inches length
  • 7 ounces weight (approx. 150 grams)
  • 9-11 rib alignment
• Position Changes with Age: Lies against the 9th, 10th, and 11th ribs

Axis of the Spleen

• Long axis along the 10th rib
• Directed downward, forward, and laterally

External Features

• Structure: 2 surfaces, 2 angles, 1 hilum
• Poles/ends: Upper and lower
• Borders:
  • Anterior (upper border)
  • Posterior (lower border)
  • Middle (intermediate border)
• Location: Behind the mid-axillary line
• Hilum: Lies between stomach and left kidney

Visceral and Peritoneal Relations

• Peritoneal Relations:
  • Spleen suspended by ligaments or folds of peritoneum
  • Greater omentum passes from hilum to greater curvature of stomach forming gastrosplenic ligament
• Short Gastric Arteries: Supply the spleen, branches of the splenic artery
• Visceral Relations:
  • Concave visceral surface towards other organs
  • Hilum: Tail of pancreas

Enlarged Spleen

• Size: Up to 300-400 grams
• Palpation: Identified by anterior border notch
• Anatomical Changes: Glides with diaphragm and abdominal wall

Development of the Spleen

• Embryonic Development: Begins in the 5th week
• Origin: Mesodermal cells in dorsal mesogastrium
• Splenunculi/Splenunculus: Accessory spleens, found in 20% population, ≤2cm in size

Blood Supply

• Splenic Artery: Branch of celiac trunk with serpentine appearance
• Circulation Types:
  • Closed circulation: Continuous endothelium
  • Open circulation: Blood flows through cavernous spaces

Clinical Aspects

• Splenic Rupture: Common in left side traumatic injuries, associated with lower rib fractures
• Symptoms of Rupture: Hypotension, tachycardia, restlessness, shock
• Referred Pain: Left shoulder due to phrenic nerve irritation
• Ballance's Sign: Dull percussion without shifting due to clotting blood

Summary

• Anatomy, position, and dimensions of the spleen
• How to hold and examine the spleen during a practical exam
• Visceral and peritoneal relations
• Important signs and clinical relevance
• Development and accessory spleens

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