Abdominal wall and fascial planes
The abdominal wall is the setting for a generation of fascial-plane regional blocks (the TAP, rectus sheath, quadratus lumborum and erector spinae plane blocks) that have transformed analgesia for abdominal surgery, and for the laparoscopic port sites and surgical incisions of the abdomen. The framework rests on six exam-critical ideas. First, the anterolateral abdominal wall is built of nine layers from superficial to deep: skin, subcutaneous fat (Camper's fascia), the membranous layer (Scarpa's fascia), the three flat muscles (external oblique, internal oblique, transversus abdominis) with their aponeuroses, the transversalis fascia, the extraperitoneal fat, and the parietal peritoneum. Second, the midline is closed by the LINEA ALBA, the fusion of the three aponeuroses, into which the rectus abdominis muscles sit either side wrapped in the RECTUS SHEATH; the sheath's composition changes at the ARCUATE LINE (about halfway between the umbilicus and the pubis), below which the posterior wall is transversalis fascia only. Third, the wall is innervated segmentally by the thoracoabdominal nerves (the anterior rami of T7 to T11), the SUBCOSTAL nerve (T12) and the ILIOHYPOGASTRIC and ILIOINGUINAL nerves (L1); the motor and sensory branches of T7-L1 run in the fascial plane between the internal oblique and transversus abdominis — the TRANSVERSUS ABDOMINIS PLANE (TAP). Fourth, the TAP block deposits local anaesthetic in this plane to anaesthetise the anterior abdominal wall (the anterolateral skin and the parietal peritoneum), giving analgesia for lower-abdominal surgery such as caesarean section, hysterectomy and hernia repair. Fifth, the related fascial-plane blocks target planes at different depths and spread — the RECTUS SHEATH block (between rectus and posterior sheath, for midline incisions), the QUADRATUS LUMBORUM block (the pararenal plane, which can spread to the thoracic paravertebral space and cover the visceral as well as the somatic abdominal wall), and the ERECTOR SPINAE PLANE block (the plane over the erector spinae, with cranial-caudal spread for thoracic and abdominal wall analgesia). Sixth, the inguinal canal and the surface landmarks (umbilicus at L4/L5, McBurney's point at the appendix, the semilunar line of the rectus border) complete the applied anatomy for hernia surgery and port placement. Built on the TAP-versus-ilioinguinal-iliohypogastric study (Reda 2026), the hyaluronidase-TAP study (Amin 2026), the erector-spinae-versus-paravertebral study (Turhan 2026), the classical-versus-deep rectus-sheath study (Chooklin 2026), the combined quadratus-lumborum study (Ji 2026), the inguinal-hernia-repair study (Filip 2026), the inguinal-canal spermatic-cord study (Tepelenis 2026), and the umbilical endometriosis study (Huang 2026).
