From the Guidelines
The urinary sphincter muscles, specifically the internal and external urethral sphincters, play a crucial role in holding urine in the bladder. These muscles work in conjunction with the bladder, a hollow, muscular organ that stores urine, to maintain urinary continence. According to a study published in the Journal of the American Academy of Child and Adolescent Psychiatry 1, urinary continence is obtained in three sequential steps: enlargement of the bladder capacity, voluntary control of the sphincter muscles, and voluntary control of the micturition reflex. The internal urethral sphincter is an involuntary muscle at the bladder neck, while the external urethral sphincter is under voluntary control. When these sphincters are closed, they prevent urine from leaking out of the bladder.
As the bladder fills, stretch receptors in its wall send signals to the brain, creating the sensation of needing to urinate, as described in the study 1. The ability to control the sphincter muscles voluntarily occurs by 3 years of age, and the final step is gaining the ability to inhibit the micturition reflex, after which urinary continence can be achieved. Problems with these sphincter muscles or the nerves controlling them can lead to urinary incontinence, where a person may experience involuntary leakage of urine. Key factors in maintaining urinary continence include:
- The internal urethral sphincter
- The external urethral sphincter
- The bladder muscle (detrusor)
- The nerves controlling these muscles, as discussed in the study 1.
From the Research
Urine Retention in the Bladder
The mechanism that holds urine in the bladder is primarily attributed to the pelvic floor muscles.
- The pelvic floor consists of levator ani muscles, including puborectalis, pubococcygeus, and iliococcygeus muscles, and coccygeus muscles 2.
- These muscles provide urethral support to prevent urine leakage and suppress urgency 2.
- The pelvic floor muscle exercise (PFME) strengthens the pelvic floor muscles, which is essential for retaining urine in the bladder 2.
- A study on the management of urinary incontinence also highlights the importance of pelvic floor exercises in managing stress urinary incontinence 3.
Role of Pelvic Floor Muscles
The pelvic floor muscles play a crucial role in holding urine in the bladder.
- The muscles work together to provide urethral support and prevent urine leakage 2.
- Weakness in the pelvic floor muscles can lead to urinary incontinence, which can be managed with pelvic floor exercises and other treatments 4, 3.
- The effectiveness of pelvic floor exercises in managing urinary incontinence has been demonstrated in various studies 2, 3.