Muscles of the Abdominal Wall Tutorial

Overview

• Functions of Abdominal Muscles:
  • Protect viscera (soft organs in abdominal cavity)
  • Assist in breathing (relax during inspiration, contract during expiration)
  • Aid in coughing and vomiting
  • Facilitate defecation, urination, and childbirth by increasing intra-abdominal pressure

Muscles of the Anterior Abdominal Wall

• Innervation: Anterior rami of spinal nerves T7-T12, L1
• Key Muscles:
  1. Rectus Abdominis
     • Location: Midline, separated by the Linea Alba (midline white line)
     • Origin: Pubic symphysis and pubic tubercle
     • Insertion: Costal cartilages and xiphoid process
     • Function: Flexes the vertebral column
     • Anatomy:
       • Linea semilunaris: edge of rectus abdominis
       • Tendinous intersections: visible in low body fat individuals
  2. Pyramidalis
     • Location: Attaches to pubis and Linea Alba
     • Innervation: Anterior ramus of T12
     • Note: Not always present

Rectus Sheath

• Structure: Tendinous sheath formed by aponeuroses of lateral muscles
• Coverage:
  • Upper three-quarters: Encloses both surfaces of rectus abdominis
  • Lower quarter: Covers only anterior surface

Lateral Abdominal Muscles

• Muscles (from superficial to deep):
  1. External Oblique
     • Origin: Ribs 5-12
     • Insertion: Iliac crest, pubic crest, pubic tubercle, Linea Alba, xiphoid process
     • Function: Flex trunk (both sides), lateral flexion (one side)
     • Fiber Direction: Inferomedial (hands in pockets mnemonic)
     • Special Structure: Forms the inguinal ligament
  2. Internal Oblique
     • Origin: Iliac crest, lateral part of inguinal ligament
     • Insertion: Ribs 9-12, Linea Alba, pubic crest
     • Function: Flex trunk (both sides), lateral flexion (one side)
     • Fiber Direction: Superomedial (hands on tits mnemonic)
  3. Transversus Abdominis
     • Origin: Iliac crest, inguinal ligament, costal cartilages
     • Insertion: Linea Alba, pubic crest
     • Function: Compresses and supports abdominal viscera
     • Fiber Direction: Transverse

Summary

• Anterior Wall Muscles: Rectus abdominis, pyramidalis (anterolateral)
• Lateral Wall Muscles: External oblique, internal oblique, transversus abdominis

This concludes the discussion on the muscles of the anterior abdominal wall, highlighting their structure, function, and attachment points.