Anterior abdominal wall muscles: rectus abdominus, internal & external oblique, transverse abdominus. Mimic a lot of anterior wall muscles. Actions of these muscles are guesses (hard to isolate) External & internal were discovered before innermost. Intercostal muscles: in between ribs (span 1 level of sibs) Attachment: inferior border of rib, superior border of rib. Attachment: nuchial ligament, spinous processes of c7-t3. Transverse tendons: breaks up rectus abdominis into parts causes rectus abdominus to do not as much flexion as you think. Origin: xyphoid process & costal cartilage on bottom of ribs. Vast majority of muscle movement from these 3 muscles. Fibres run in hands in your pockets . Insertion: linea alba (vertical line down rectus abdominus); pubic tubercle; anterior half of iliac crest. Fibers run from ilium of hip to xyphoid process. Action: rotate & laterally bend trunk; flex trunk (prime flexor!) Origin: thoracolumbar fascia, anterior 2/3 of iliac crest; connective tissue deep to inguinal ligament.