Posterior Abdominal Wall Anatomy

Layers of the Posterior Abdominal Wall

• Outer layer: Transversalis fascia (a layer of connective tissue)
• Middle layer: Posterior abdominal wall muscles (erector spinae, latissimus dorsi, and quadratus lumborum)
• Inner layer: Parietal peritoneum (a layer of peritoneum lining the abdominal cavity)

Muscles of the Posterior Abdominal Wall

• Erector Spinae:
  • Consists of three columns: iliocostalis, longissimus, and spinalis
  • Extends from the sacrum to the thorax
  • Functions: extends and rotates the vertebral column
• Latissimus Dorsi:
  • Originates from the thoracolumbar fascia and spinous processes of the lower thoracic vertebrae
  • Inserts into the humerus
  • Functions: adducts, extends, and internally rotates the shoulder joint
• Quadratus Lumborum:
  • Originates from the posterior abdominal wall and iliac crest
  • Inserts into the 12th rib
  • Functions: fixes the 12th rib during respiration and assists in lateral flexion of the vertebral column

Other Structures of the Posterior Abdominal Wall

• Lumbar Triangle:
  • A weak area in the posterior abdominal wall, bounded by the latissimus dorsi, external oblique, and iliac crest
  • A potential site for herniation
• Lumbar Plexus:
  • A network of nerves formed by the ventral branches of L1-L4
  • Supplies the lower limb
• Kidneys and Adrenal Glands:
  • Located on either side of the vertebral column
  • Protected by the posterior abdominal wall muscles and transversalis fascia

Learn about the layers and muscles of the posterior abdominal wall, including the erector spinae, latissimus dorsi, and quadratus lumborum. Understand the functions of each muscle and other structures like the lumbar triangle, lumbar plexus, and kidneys and adrenal glands.