Anatomy and Physiology: The Rectus Sheath

Introduction

• Lecturer: Kevin Tokoff at Catalyst University
• Topic: Anterior abdominal wall focusing on the rectus sheath
• Rectus sheath: protective covering for the rectus abdominis muscle

Rectus Sheath Overview

• Analogy: A sheath for a sword; protective case for the rectus abdominis
• Position: Can be anterior (in front) or posterior (behind) the rectus abdominis

Muscles and Aponeuroses

• Muscles lateral to the rectus abdominis:
  • External abdominal oblique (superficial)
  • Internal abdominal oblique (intermediate)
  • Transverse abdominis (deepest)
• Characteristics of aponeuroses:
  • Sheet-like tendons
  • Fusion of aponeuroses from these muscles forms the rectus sheath

The Arcuate Line

• A critical point determining the nature of the rectus sheath
• Divides the rectus abdominis into regions:
  • Above the arcuate line
  • Below the arcuate line

Above the Arcuate Line

• Composition of the anterior rectus sheath:
  • All of the external oblique aponeurosis
  • Half of the internal oblique aponeurosis
• Composition of the posterior rectus sheath:
  • Other half of the internal oblique aponeurosis
  • All of the transverse abdominis aponeurosis
• Fusion point: Linea alba
  • Midline fusion of aponeuroses

Below the Arcuate Line

• All three aponeuroses (external, internal oblique, and transverse abdominis) cross in front of the rectus abdominis
• Posterior to the rectus abdominis: Transversalis fascia
  • Function: Prevents rectus abdominis from contacting abdominal viscera

Key Takeaways

• Nature of the rectus sheath is dictated by position relative to the arcuate line:
  • Above: Both anterior and posterior layers exist
  • Below: All aponeuroses move anteriorly

Conclusion

• Understanding the rectus sheath structure aids in comprehending muscle and fascia interactions in the abdominal wall
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