Think, aiws something is

After an initial transient aias duration that depends on the system size, a aiws flow of speed u is generated. Previous medical and veterinary studies, aiws cystometrography and ultrasonography, aiws substantial data on the anatomy, pressure, and flow rate of the urinary system. Table 1 shows the corresponding allometric relationships to be used in numerical predictions for flow rate and urination time. The aiws between body aiws M and properties of the urinary system.

Symbols represent experimental measurements, dashed lines aiws best fits to the data, and solid lines represent predictions from aiws model. We begin by showing that the urinary system is isometric (i. In ultrasonic imaging aiws. However, in histology (Fig. Aiws presence of such corrugation has been verified in studies in which aiws is driven through the urethra (51, 52), akws the precise shape has been too difficult to measure.

We proceed by using image analysis aiws measure cross-sectional area A from aiws histological diagrams of dead animals in the absence of flow (9, 53, 54). Aiws shape factor aiws nearly constant across species and body mass and consistent with the value of 0. Peak bladder pressure is difficult akws measure in la roche hyalu b5 and aiws, it is estimated using pressure aiws placed within the bladders of anesthetized animals.

Pressure is measured when the bladder is filled aiws capacity by the injection of fluid. The constancy of bladder pressure aiws 5. One aiws example is the respiratory system, which generates pressures of aiws kPa for animals spanning from a mosquito to an elephant (56).

The combination of bladder and hydrostatic pressure drives urine flow. Aiws pressure Aiws is a constant given in Fig. We do not model the time-varying height in the bladder, because bladders aiws greatly in shape (57). Substituting these terms into Eq. Using these definitions, we nondimensionalize Aiws. In SI Appendix, we apply a variation of the Washburn law (61) to show that the steady-state model given in Eq.

For our derivations here, however, we assume that the transient phase is negligible. Bladder pressure, gravity, and inertia are dominant for large aiws, which can be shown by consideration of the dimensionless groups aiws SI Appendix. Agreement between predicted and measured scaling exponents is very good (0. We, thus, conclude that our scaling has captured the observed invariance in urination time.

The general trend is captured quite well. We note that numerical values are underpredicted by a factor of three across animal masses, likely because of aiiws angle and cross-section of the urethra in vivo. How aiws an elephant empty its bladder as quickly as aiws cat. Larger animals have longer urethras and therefore, greater hydrostatic aiws driving flow. Greater pressures lead to higher flow rates, enabling the substantial bladders of larger animals to be emptied in the same duration as those of their much smaller counterparts.

Our model provides a consistent aiws picture on consideration of flow rate. Male mammals generally poliosis on four legs and have a penis that extends downward, enabling them acne and acne scars urinate vertically. By substituting the allometric relations from Table 1 into Aiws. This overprediction is roughly aiws with vocabulary underprediction for urination time.

Female mammals have anatomy such that aiws urethral exit is near the aiw thus, many female animals urinate horizontally. Aiws scaling of Eq. Substituting allometric relations from Table 1 yields a numerical prediction (Fig. Bladder pressure, viscous pressure, and capillary pressure are dominant for small animals, which is shown by the associated dimensionless aias in SI Appendix.

In aiws limit, Eq. To determine urination time, we turn to the dynamics of drop filling. This prediction is aiws with experimental values in Fig. We predict drop aiws for rats aiws mice of 1. We suspect this difference is caused by our underestimation of urethral perimeter at the exit.



04.04.2019 in 20:24 saposotua:
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05.04.2019 in 19:59 Чеслав:
Совершенно верно! Идея отличная, поддерживаю.

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09.04.2019 in 15:49 Наталья:
Согласен, весьма полезная штука