EDAPT The Urinary System Practice Test 2026 - Free Practice Questions for Urinary System Study and Review

The detrusor muscle is a crucial component of the urinary system, playing a significant role in the process of urination. This smooth muscle forms the muscular layer of the bladder wall and is responsible for contracting to expel urine during the process of micturition, or urination. When the bladder fills with urine, stretch receptors send signals to the nervous system, initiating contraction of the detrusor muscle. This contraction helps to increase the pressure within the bladder, allowing urine to flow into the urethra and out of the body.

Other muscles mentioned serve different functions. The rectus abdominis is primarily involved in movements of the torso and does not play a direct role in bladder function. The psoas major is involved in hip flexion and spinal stabilization, while the external urethral sphincter is responsible for the voluntary control of urination, helping to retain urine until it is appropriate to void. While the external urethral sphincter is involved in the urination process, it does not facilitate the actual expulsion of urine like the detrusor muscle does. Thus, the detrusor muscle is key in facilitating urination through its contraction.