Experimentation and modelling of the human oesophagus
2021
The oesophagus is a primarily mechanical organ which transports food from the pharynx to the stomach
through a series of muscular contractions. As of yet, the passive mechanical properties of the human
oesophagus have not been established [1]. This is essential for proper investigation into how clinical
diseases affect the oesophagus’ primary function. Further to this, mechanical data on the oesophagus
has applications within tissue engineering [2], and computational models formed from this data can be
used to enhance medical device design and surgical simulations [3]. Currently, the vast majority of ex
vivo experimentation on the oesophagus has been carried out using animal tissue [2]. While this may
give a good representation of how human tissue might behave, it cannot be used to accurately model the
human oesophagus for applications within medicine. The oesophagus is one of the few visceral organs that
can be separated into two distinct layers; the mucosa-submucosa and the muscularis propria. Currently,
outside of this author’s work [4], the human oesophagus has not been studied in regard to its layerdependent properties. This work investigates the layer-dependent properties through a series of increasing
deformation level cyclic tests performed under uniaxial tension. First, the oesophagus was explanted
by means of dissection. Next, the organ was separated into the two main layers. Specimens were then
tested in both the longitudinal and circumferential directions to observe any anisotropy. The cyclic tests
were conducted at two different strain rates and included two cycles per deformation level to observe
the pre-conditioning behaviour. The results displayed anisotropic behaviour, with greater stiffness in the
longitudinal direction than the circumferential direction for both of the layers. The mucosa-submucosa
was found to be stiffer than the muscularis propria layer in both directions. The observed behaviours
were then modelled using two different models. For the first, the first loading path of each deformation
level was extracted and an anisotropic, hyperelastic matrix-fibre model based on histological observations
was used to simulate the hyperelastic behaviour. Next, the viscoelastic behaviour and stress-softening of
the tissue were captured through modelling of the cyclic testing results. Both models produced a good fit
with the experimental data.
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