02/17/2026
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Diaphragm & Posterior Abdominal Wall Anatomy
The diaphragm is the primary muscle of respiration, forming a dome-shaped partition between the thoracic and abdominal cavities. Its muscular fibers originate from the ribs, sternum, and lumbar vertebrae, converging into the central tendon, which acts as the main aponeurotic support. When the diaphragm contracts, it flattens and increases thoracic volume, allowing air to enter the lungs.
At the center of the diaphragm lies the caval opening, which allows passage of the inferior vena cava. This opening is positioned within the central tendon so that diaphragmatic contraction helps facilitate venous return to the heart. Slightly posterior is the esophageal hiatus, where the esophagus passes through along with the vagus nerves. The diaphragmatic fibers around this opening help prevent gastric reflux by acting as a physiological sphincter.
Further posterior lies the aortic hiatus, which transmits the abdominal aorta, thoracic duct, and azygos vein. Unlike the esophageal opening, this hiatus is formed by the crura and is not affected by diaphragmatic contraction, ensuring uninterrupted blood flow.
The right and left crura of the diaphragm anchor the muscle to the lumbar vertebrae, providing structural stability and assisting in diaphragmatic movement. The right crus is typically longer and contributes to forming the esophageal hiatus. Adjacent to these structures is the lumbocostal trigone, a small triangular gap that can be a site of congenital diaphragmatic hernia.
Below the diaphragm lie important posterior abdominal wall muscles. The psoas major originates from the lumbar vertebrae and travels to the femur, functioning as a powerful hip flexor and stabilizer of the lumbar spine. The psoas minor, when present, assists in lumbar stabilization. The iliacus muscle lines the iliac fossa and joins the psoas major to form the iliopsoas, which is essential for hip flexion and posture.
This anatomical region is crucial not only for breathing but also for posture, spinal stability, circulation, and core function. Tightness or dysfunction of the diaphragm and iliopsoas complex can influence breathing patterns, lower back mechanics, and movement efficiency.
Understanding the diaphragm and its surrounding structures highlights the integration between respiration, core stability, and movement, making it essential knowledge for clinicians, physiotherapists, and movement specialists.