Résumé
Perineal tears affect the majority of primiparous women during vaginal delivery and may involve multiple tissue layers, leading to long-term functional impairments. Despite their prevalence, the mechanical behaviour of perineal tissues remains insufficiently characterised, limiting the reliability of biomechanical models used to study childbirth-related injuries. This study provides a comprehensive multiscale characterisation of the mechanical behaviour and structural organisation of five perineal tissues using ex vivo porcine samples: skin, vaginal mucosa, anal mucosa, and internal and external anal sphincters.Uniaxial tensile tests were performed on dog-bone specimens cut along two perpendicular directions to assess anisotropy, except for the external anal sphincter, which was tested along its principal fibre direction. Cyclic loading at increasing strain levels up to rupture was applied to reproduce labour-like loading conditions, with digital image correlation used for accurate strain measurement. Tissue mechanical responses were quantified through inverse identification of hyperelastic parameters using a Veronda–Westmann model. Mechanical testing was complemented by structural analysis across multiple scales. Two-photon excitation microscopy enabled quantitative assessment of collagen fibre organisation at the microscale, while micro-computed tomography provided three-dimensional insights into the architecture of full perineal samples.Distinct mechanical behaviours were observed among the tissues: vaginal and anal mucosae were the stiffest, skin showed intermediate stiffness, and the sphincters were the most compliant, with marked direction-dependent behaviour in the internal anal sphincter. Structural imaging revealed tissue-specific collagen architectures consistent with these findings, while micro-CT confirmed the anisotropic architecture of the sphincters and highlighted the folded morphology of the anal mucosa and skin. Overall, this study establishes baseline mechanical and structural markers for perineal tissues, emphasising their anisotropy, variability, and layered complexity. Future investigations will focus on characterising the high-rate, viscoelastic behaviour of these tissues.