Microstructure-based constitutive modeling for the large intestine validated by histological observations.

Area of Science:

• Gastrointestinal Physiology
• Biomedical Engineering
• Tissue Mechanics

Background:

• The large bowel's complex functions, including absorption, are optimized by contractile and recoil properties.
• These biomechanical properties are less understood compared to other GI tract regions.

Purpose of the Study:

• To investigate the pseudo-elastic properties of rat large bowel tissue.
• To develop a microstructure-based material model for colon tissue.

Main Methods:

• In vitro analysis of tubular specimens from rat ascending, mid, descending colon, and rectum.
• Application of a neo-Hookean and three-fiber (diagonal and axial) family model.
• Histological analysis of collagen and elastin content.

Main Results:

• The neo-Hookean and three-fiber model accurately represented colon tissue mechanics without over-parameterization.
• Collagen fiber alignment towards the axial direction increased tissue stiffness.
• The mid-colon was the stiffest region due to higher collagen content.

Conclusions:

• The study provides a histomechanical understanding of the large bowel.
• Findings have potential for clinical and biomedical applications in understanding bowel function and disease.