A realistic finite element model of the human gastro-oesophageal junction

Abstract

The aim of the research described in this thesis is to improve the understanding of the function of the gastro-oesophageal junction both in normal and disease states using mathematical modelling. An anatomically-realistic three-dimensional finite element model of the oesophagus and the gastro-oesophageal junction was constructed using cross-sectional images obtained from the Visible Human Project®. Governing equations of finite elasticity were incorporated into the finite element model. These equations were solved numerically to investigate the muscle contraction of the gastro-oesophageal junction during swallowing. The model was capable of producing realistic intraluminal pressure values. During the contraction of a normal gastro-oesophageal junction, the model predicted a resting pressure value of 25.80 mmHg (3.44 kPa). The model was also used to represent a hypo- and a hypertensive junction as occurs in gastrooesophageal reflux disease and in achalasia respectively. The resting pressures predicted by the model in these settings were found to be 2.60 mmHg (0.35 kPa) and 31. 73 mmHg ( 4.23 kPa) respectively. To obtain a better understanding of the structures within and around the gastrooesophageal junction, detailed studies were made using an · en-bloc harvest excised from a recently deceased human cadaver. The excised tissue was fixed and embedded in wax resulting in a 75x75x55 mm 3 tissue block. The tissue block was then mounted on a custom-built imaging system to obtain high-resolution (8.2 μm/pixel) crosssectional images of the tissue block. A three-dimensional representation of the gastrooesophageal junction was then reconstructed using the high-resolution cross-sectional images.