- Origins
- 8 digitations, one from each of the lower 8 ribs
- The lower 4 interdigitate with the costal fibres of Latissimus Dorsi and the upper 4 interdigitate with Serratus Anterior
- Free posterior border extends from 12th rib to anterior half of the outer lip of the Iliac Crest
- Muscular fibres replaced by aponeurosis:
- Below a line joining ASIS to umbilicus
- Medial to a vertical line drawn from the tip of the 9th costal cartilage
- Aponeurotic fibres interdigitate with each other across the front of rectus abdominis along the whole length of the Linea Alba
- Free horizontal upper border of this aponeurosis extends from 5th rib to xiphisternum
- Only structure in the anterior sheath of the rectus muscle above the costal margin
- Lower border forms Inguinal Ligament (of Poupart) – between ASIS and pubic tubercle
- Edge rolled inwards – lateral part gives origin to part of the internal oblique and transversus abdominis muscles
- Fascia Lata of thigh attached to Inguinal Ligament
