Muscles of the Anterior and Lateral Abdominal Wall

Question 1

External Abdominal Oblique

Answer 1

Origin: lateral portion of lower eight ribs
Insertion: via broad tendinous sheath called aponeurosis into midline tendinous sheath called linea alba; also inserts into pubis
Action: bilateral contraction compresses abdominal wall, flexes vertebral column; unilateral contraction rotates trunk

Question 2

Internal abdominal Oblique

Answer 2

Origin: iliac crest and lumbar vertebrae (via broad fascia)
Insertion: linea alba via aponeurosis, lower ribs, pubis
Action: compresses abdominal wall

Question 3

Transversus Abdominis

Answer 3

Origin: iliac crest, lumbar vertebrae (via broad fascia), lower ribs
Insertion: linea alba, pubis
Action: compresses abdominal wall

Question 4

Rectus Adominis

Answer 4

Origin: pubis
Insertion: xiphoid process and costal cartilage of ribs 5-7
Action: flexes vertebral column as during a sit-up compresses abdominal wall