POL Scientific / Bladder / Volume 11 / Issue 3 / DOI: 10.14440/bladder.2024.0029
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REVIEW

Urethral pharmacological mechanisms incontinence and bladder emptying: An updated review

Karl-Erik Andersson1,2* ,  Bengt Uvelius3,4
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1 Department of Regenerative Medicine, Faculty of Medicine, Wake Forest Institute for Regenerative Medicine, Winston-Salem, North Carolina, 27101 United States
2 Department of Laboratory Medicine, Faculty of Medicine, Lund University, Lund, 22184 Sweden
3 Department of Urology, Skåne University Hospital, Malmö, 21421 Sweden
4 Department of Clinical Sciences Lund, Faculty of Medicine, Lund University, Lund, 22184 Sweden
Bladder 2024 , 11(3), e21200015; https://doi.org/10.14440/bladder.2024.0029
Submitted: 6 August 2024 | Revised: 19 August 2024 | Accepted: 8 October 2024 | Published: 28 November 2024
© 2024 by the Bladder published by POL Scientific. Licensee POL Scientific, USA. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

Background: The urethral wall consists of layers of striated muscle, circular and longitudinal smooth muscles, collagen fibers, and a vascular plexus. However, the relative contributions of these components to urethral pressure in humans remain poorly understood. The circular and longitudinal smooth muscle components can develop a spontaneous contractile activity, generating a basal tone. They can further contract or relax in response to excitatory or inhibitory stimuli. Animal studies suggest that smooth muscle activity in the mid-urethra plays a crucial role in determining maximal urethral closing pressure. Notably, the highest sympathetic activity occurs in the middle segment of the female urethra during increasing smooth muscle tone. This finding is supported by human studies that did not detect any electromyographic activity from striated muscle in this region. Objectives: This study was conducted to review the contributions of the primary structural components and control mechanisms of urethral. Conclusion: In females, the external urethral striated sphincter is located at the distal urethra, which is not the segment associated with the highest closing pressure. Rather, the sphincter has been shown to modulate urethral pressure during exercise and physical stress. Basic science research does not support the notion that mid-urethral pressure is caused by the external striated sphincter tone in females. Instead, findings suggest that, at rest and during bladder filling, maximal urethral pressure is primarily determined by the activity of the urethral smooth muscles.

Keywords
Urethra
Striated muscle
Smooth muscle
Vascular plexus
Funding
None.
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Conflict of interest
The authors declare no conflicts of interest.
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Bladder, Electronic ISSN: 2327-2120 Print ISSN: TBA, Published by POL Scientific
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