Final answer:
Ureters travel down the anterior surface of the psoas major muscle as they move urine from the kidneys to the bladder.
Step-by-step explanation:
The ureters are tube-like structures that carry urine from the kidneys to the urinary bladder. They arise at the renal pelvis of the kidney and travel down through the abdomen. On their course through the posterior abdominal wall, the ureters travel down on the anterior surface of the psoas major muscle. This muscle, along with the iliacus, forms part of the floor of the posterior abdominal wall and plays a role in stabilizing the body and maintaining posture. The psoas major is responsible for flexing the hip and stabilizing the lumbar spine, while the ureters function in transporting urine by peristalsis.