The effect of urinary bladder shape on its mechanics during filling

Damaser, Margot S.; Lehman, Steven L.

doi:10.1016/0021-9290(94)00169-5

Cited by 54 publications

(44 citation statements)

References 17 publications

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“…Included among these forces are the contractile properties of vesical smooth muscle due to their sympathetic and parasympathetic input as well as the inherent mechanical constituents of the tissue [Dorr, 1993;Khadra et al, 1995]. Recent observations have shown that bladder stiffness is modified by central innervation [Skehan et al, 1993a,b], geometry [Damaser and Lehman, 1995], pathology such as chronic obstruction [Damaser et al, 1996], and endogenous factors [Dorr, 1993]. While bladder wall stiffness can be measured in vivo from the CMG during filling, direct recordings of the stiffness of the bladder wall under isometric conditions, at zero volume, or during the micturition cycle have not been reported.…”

Section: Introductionmentioning

confidence: 99%

Comparative analysis of bladder wall compliance based on cystometry and biosensor measurements during the micturition cycle of the rat

et al. 1997

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Section: Introductionmentioning

confidence: 99%

Comparative analysis of bladder wall compliance based on cystometry and biosensor measurements during the micturition cycle of the rat

et al. 1997

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“…Overall stress and stretch values in the longitudinal and circumferential directions were smaller for a prolate spheroid except near the equator in which they were both larger than a sphere in the circumferential direction (Damaser and Lehman, 1995). In addition, stretch values were the same far from the equator, but circumferential stretches were larger than longitudinal stretches as the equator was approached (Damaser and Lehman, 1995).…”

Section: Estimated Wall Stress Responsesmentioning

confidence: 82%

“…They showed that the pressure-volume results for a prolate spheroid indicated increased compliance but differed only slightly from a sphere for all eccentricities, a measure of the deviations from a sphere (Damaser and Lehman, 1993). Overall stress and stretch values in the longitudinal and circumferential directions were smaller for a prolate spheroid except near the equator in which they were both larger than a sphere in the circumferential direction (Damaser and Lehman, 1995). In addition, stretch values were the same far from the equator, but circumferential stretches were larger than longitudinal stretches as the equator was approached (Damaser and Lehman, 1995).…”

Section: Estimated Wall Stress Responsesmentioning

confidence: 99%

Ex vivo deformations of the urinary bladder wall during whole bladder filling: Contributions of extracellular matrix and smooth muscle

Parekh

Cigáň

Wognum

et al. 2010

Journal of Biomechanics

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“…3D. We do not model the time-varying height in the bladder, because bladders vary greatly in shape (57). Thus, hydrostatic pressure scales with urethral length: P gravity ∼ ρgL, where g is the acceleration of gravity.…”

Section: Steady-state Equation Ofmentioning

confidence: 99%

Duration of urination does not change with body size

Yang¹,

Pham²,

Choo³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Many urological studies rely on models of animals, such as rats and pigs, but their relation to the human urinary system is poorly understood. Here, we elucidate the hydrodynamics of urination across five orders of magnitude in body mass. Using high-speed videography and flow-rate measurement obtained at Zoo Atlanta, we discover that all mammals above 3 kg in weight empty their bladders over nearly constant duration of 21 ± 13 s. This feat is possible, because larger animals have longer urethras and thus, higher gravitational force and higher flow speed. Smaller mammals are challenged during urination by high viscous and capillary forces that limit their urine to single drops. Our findings reveal that the urethra is a flow-enhancing device, enabling the urinary system to be scaled up by a factor of 3,600 in volume without compromising its function. This study may help to diagnose urinary problems in animals as well as inspire the design of scalable hydrodynamic systems based on those in nature.urology | allometry | scaling | Bernoulli's principle M edical and veterinary urology often relies on simple, noninvasive methods to characterize the health of the urinary system (1, 2). One of the most easily measured characteristics of the urinary system is its flow rate (3), changes in which may be used to diagnose urinary problems. The expanding prostates of aging males may constrict the urethra, decreasing urine flow rate (4). Obesity may increase abdominal pressure, causing incontinence (5). Studies of these ailments and others often involve animal subjects of a range of sizes (6). A study of urination in zero gravity involved a rat suspended on two legs for long periods of time (7), whereas other studies involve mice (8), dogs (1), and pigs (9). Despite the wide range of animals used in urological studies, the consequences of body size on urination remain poorly understood.The bladder serves a number of functions, as reviewed by Bentley (10). In desert animals, the bladder stores water to be retrieved at a time of need. In mammals, the bladder acts as a waterproof reservoir to be emptied at a time of convenience. This control of urine enables animals to keep their homes sanitary and themselves inconspicuous to predators. Stored urine may even be used in defense, which one knows from handling rodents and pets.Several misconceptions in urology have important repercussions in the interpretation of healthy bladder function. For instance, several investigators state that urinary flow is driven entirely by bladder pressure. Consequently, their modeling of the bladder neglects gravitational forces (11-13). Others, such as Martin and Hillman (14), contend that urinary flow is driven by a combination of both gravity and bladder pressure. In this study, we elucidate the hydrodynamics of urination across animal size, showing the effects of gravity increase with increasing body size. ResultsIn Vivo Experiments. We filmed the urination of 16 animals and obtained 28 videos of urination from YouTube, listed in SI Appendix. Movies ...

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The effect of urinary bladder shape on its mechanics during filling

Cited by 54 publications

References 17 publications

Comparative analysis of bladder wall compliance based on cystometry and biosensor measurements during the micturition cycle of the rat

Comparative analysis of bladder wall compliance based on cystometry and biosensor measurements during the micturition cycle of the rat

Ex vivo deformations of the urinary bladder wall during whole bladder filling: Contributions of extracellular matrix and smooth muscle

Duration of urination does not change with body size

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