Final answer:
The iliopsoas is composed of the psoas major and iliacus muscles. These muscles come together in the gluteal region and play a role in flexing the thigh at the hip joint.
Step-by-step explanation:
The iliopsoas is composed of two muscles - the psoas major and the iliacus. These two muscles come together in the gluteal region and form the iliopsoas, which plays a role in flexing the thigh at the hip joint. The psoas major originates from the lumbar vertebrae and the iliacus originates from the iliac fossa of the pelvis.