Final answer:
The external abdominal oblique muscle originates from the lower 8 ribs and inserts into the linea alba and pubic tubercle. Its main action is to produce trunk rotation and lateral flexion.
Step-by-step explanation:
The external abdominal oblique muscle originates from the lower 8 ribs and inserts into the linea alba and pubic tubercle. Its action includes contraction of one side which results in ipsilateral trunk rotation and lateral flexion, while contraction of both sides produces flexion of the trunk.