Background and Purpose: Most current studies on the passive biomechanical properties of esophageal tissues directly use the exponential strain energy function (SEF) to fit and calculate the constants of the constitutive equation. In the context of the extensive application of exponential SEF, in-depth research on the exponential SEF is still lacking. The purpose of this study is to combine the exponential function with the polynomial SEF to obtain the most suitable constitutive equation to describe the three-dimensional passive behavior of the esophagus. Methods: fresh pig esophagus with a length of 13 cm in the middle position was selected as esophageal samples. The esophageal sample was separated into muscular layer and mucosal layer with surgical scissors. Stretch–inflation mechanical tests of the intact esophagus, esophageal muscular, and esophageal mucosa were carried out on a triaxial test machine. The external radius, axial force, and internal pressure were recorded simultaneously. The seven-parameter Fung-type SEF and several new SEFs combining polynomials and exponents were used to fit the experimental data curves. Results: The stretch–inflation test data and the morphometric parameters at the zero-stress state of the layered esophagus were obtained. The new SEF with polynomial and exponential combination is more suitable to describe describing the three-dimensional passive biomechanical properties of esophageal tissue. Among them, New-Fung13 SEF is more suitable for describing the passive biomechanical properties of intact esophageal tissue, Sokolis-Fung13 SEF is more suitable for the esophageal muscle layer, and New-Fung10 SEF is more suitable for the esophageal mucosa. The constitutive parameters of the optimal constitutive model for each layer of the esophagus were obtained.

背景与目的：目前大多数关于食管组织被动生物力学特性的研究直接使用指数应变能函数（SEF）来拟合和计算本构方程的常数。在指数SEF广泛应用的背景下，仍缺乏对指数SEF的深入研究。本研究的目的是将指数函数与多项式SEF相结合，以获得最适合描述食管三维被动行为的本构方程。方法：取新鲜猪食道中段长13 cm作为食道标本。用手术剪将食管样本分为肌层和黏膜层。完整食道、食道肌肉、和食管黏膜在三轴试验机上进行。同时记录外径、轴向力和内压。使用七参数 Fung 型 SEF 和几个结合多项式和指数的新 SEF 来拟合实验数据曲线。结果：获得了分层食管在零应力状态下的拉伸-膨胀试验数据和形态学参数。新的多项式和指数组合的SEF更适合描述食管组织的三维被动生物力学特性。其中，New-Fung13 SEF更适合描述完整食管组织的被动生物力学特性，Sokolis-Fung13 SEF更适合于食管肌肉层，New-Fung10 SEF更适合于食管黏膜。