The large region of the anterior abdominal wall from the xiphoid process and costal arches to the pelvic bones has a typical layered architecture: Below the skin and subcutaneous fat tissue are superficial fascias, muscles and their fascias, then the extraperitoneal fascia and finally parietal peritoneum.
Particularly in the anterior wall inferior to the umbilicus, the otherwise typical single-layered superficial abdominal fascia in the fatty subcutaneous tissue (panniculus adiposus abdominis) transitions into a dual-lamina structure comprising a superficial lamina (Camper fascia) and a deeper, membranous layer (Scarpa fascia or fascia investiens abdominis). The five abdominal muscles comprise:
3 oblique muscles (1. external oblique muscle of abdomen, 2. internal oblique muscle of abdomen, and 3. transverse abdominal muscle).
2 straight muscles (4. M. rectus abdominis muscle and the inconstant 5. Pyramidal muscle).
- External muscle
Located just below the superficial fascia, it extends mediocaudad to the abdominal aponeurosis, with both sides fusing midline to the white line (linea alba). Caudad It is bordered by the inguinal ligament from the superior anterior iliac spine to the pubic tubercle, which in turn divides mediad into the lacunar ligament and the pectineal ligament (Cooper). - Middle muscle
Its fibers run craniomediad, fusing with fibers from 1. to the white line - Internal muscle
transverse fibers, also radiating into the white line.
Each of the three oblique abdominal muscles is invested by its own thin fascia , 3. on its inner aspect the strong transverse fascia. This fascia lines the abdominal cavity and fuses craniad with the diaphragmatic fascia and posteriad with the thoracolumbar fascia. Caudad, it is attached to the iliac crest and fuses with the endopelvic fascia.
Long straight paired abdominal muscle, interrupted by 3 - 4 transverse tendinous intersections ("six-pack").
Triangular rudimentary muscle caudad and anteriad to 4. between the pubic bone and white line.
