## 3 Results and Discussion
### Experimental Results  
Figures 6 and 7 present the individual longitudinal and circumferential curves obtained experimentally, along with their respective mean curves. In Figure 6, the longitudinal curves correspond to the validated mechanical tests (#3). For each cycle of the mean curve, with corresponding stretch values (\(\lambda\) = 1.1, 1.2, 1.3, 1.4, 1.5, 1.75 and 2.0), the peak stress values are 7, 9, 17, 26, 38, 70 and 106 kPa, respectively. The circumferential results are shown in Figure 7, where the validated experimental data (#3 samples) and the mean curve are represented. At the peak of each cycle (\(\lambda\) = 1.1, 1.2, 1.3, 1.4, 1.5, 1.75 and 2.0), the maximum stress is 7, 8, 12, 18, 24, 47 and 74 kPa, respectively. At each cycle, the longitudinal samples achieved higher peak stress values when compared to the circumferential samples. This could be justified by the orientation of the fibres, which is different for each type of sample. The fibre contribution makes the longitudinal samples stiffer, a phenomena well documented in the literature [26; 32; 33]. Comparing the current results (porcine urethra) with the human data from [PERSON] et al. (human urethra) [26], we can point out both similarities and differences. In Figure 8 (longitudinal urethra), the shape similarities between the porcine experimental data (current study) and the results achieved by [PERSON] et al. for the human urethra (using the same experimental protocol) are evident. Still, the results from [PERSON] et al. (full line) are'softer' than the porcine results (long dashed line). The porcine results' curve (current study) is always above the human results ([PERSON], [26]) even if the standard deviation (STD) of the pig data (grey ribbon) is taken into consideration. However, these differences are smaller by considering the mean curve of the pig data minus the STD (\(\sigma\)-STD). Figure 5: Boundary conditions and displacement imposed to the mesh to conduct FEM simulations. The FEM model mimics the experimental procedure. Figure 6: Experimental results and mean curve corresponding to the longitudinal samples from porcine urethra. Figure 7: Experimental results and mean curve corresponding to the circumferential samples from porcine urethra. Recently, [PERSON] et al. [25] have studied the mechanical behaviour of the human male urethra, and their results have important differences when compared to those of [PERSON] (human) and the current study (porcine). The longitudinal tensile curves (and the circumferential, which are identical) evidenced much lower stresses for every stretch level considered. The maximum stress achieved, corresponding to the last stretch level considered (\(\lambda\approx 2\)), was \(\approx\)6 kPa. The porcine results (this work) can also be compared with the data from [PERSON] et al. [4] for the horse urethra. For a \(\lambda=1.6\) (60% deformation), these authors obtained a corresponding stress which is approximately half of the porcine results. These differences point to a difference in the stiffness between the tissues (porcine and equine urethrae) in the longitudinal orientation. A comparison of the experimental data for the circumferential urethrae (porcine--current study vs. human--[PERSON] et al. [25]) is presented in Figure 9. The overall mechanical behaviour of both tissues (the curve shape of full and dashed lines) is different. However, several peak maxima (the maximum stress of the load region) have identical intensities if we consider the variability associated with the STD. Considering the tensile test results from [PERSON] et al. [25] (human urethra), the specimens tested in a circumferential orientation showed consistently smaller stress levels (\(\approx\)6 kPa for a \(\lambda\approx 1.9\)) when compared with the porcine results. Comparing the mechanical behaviour in both studies up to their common stretch (\(\lambda=1.6\)), they have a modulus in the same order of magnitude, 48 and 39 kPa, respectively. Recently, [PERSON] et al.