A micromechanical model for the Young’s modulus of adipose tissue

Abstract

a b s t r a c tThe microstructure of porcine adipose tissue is examined, and a micromechanical model is proposed for the dependence of overall effective modulus upon the moduli of the constituent microstructural units. Scanning electron microscopy and confocal microscopy reveal that the woven collagen network surrounding each adipocyte resembles a closed cell foam of relative density q m ¼ 0:1, while the collagen interlobular septa behave as an open cell foam of relative density q s ¼ 3 Â 10 À4 . The measured viscosity of the lipid within the adipocytes is g = 36.8 mPa s at 37°C; this is sufficiently small for the lipid to be idealised as an incompressible inviscid fluid. It is argued that the modulus of adipose tissue is dictated by the collagen network that surrounds the adipocytes. The volume fraction of the interlobular septa is sufficiently low that it provides a negligible contribution to the macroscopic modulus.

The evaluation of new multi-material human soft tissue simulants for sports impact surrogates

“…The smaller network is a reinforcement basement membrane, comprised of collagen fibres, which acts as the walls of a closed cell foam with the adipocyte forming the cavity. The larger network is called the interlobular septa comprised of type I collagen fibres and is roughly 1mm in size acting as an open celled foam (Comley & Fleck, 2010). Adipose, as with most biological tissues, exhibits heterogeneous, rate-dependent, viscoelastic behaviour and experiences large non-linear deformations (Holzapfel, 2004;Sapozhnikov & Ignatova, 2013).…”

“…Adipose, as with most biological tissues, exhibits heterogeneous, rate-dependent, viscoelastic behaviour and experiences large non-linear deformations (Holzapfel, 2004;Sapozhnikov & Ignatova, 2013). It is suggested that adipose is approximately isotropic in structure and due to the large liquid content is almost incompressible (Samani et al, 2003;Comley & Fleck, 2010), though a recent study by Sommer et al (2013) observed some anisotropy in specimens.…”

“…Azar et al, 2002;Krouskop et al, 1998;Van Houten et al, 2003;Sarvazyan et al, 1994;Samani et al, 2007) or porcine subcutaneous specimens (e.g. Geerligs et al, 2008;Comley & Fleck, 2010;Comley & Fleck, 2012), which have been shown to exhibit similarities in morphology, histology, and overall mechanical response with human tissues (Douglas et al, 1972;Paus et al, 2007).…”

Intermittent Pneumatic Compression Enhances Formation of Edema Tissue Fluid Channels in Lymphedema of Lower Limbs

“…The modulus of adipose tissue is dictated by the collagen network that surrounds the adipocytes. 18 This causes that edema fluid tries to find its way also around fat globules.…”

Deep penetration and liquid injection into adipose tissue

“…Uniaxial compression tests of adipose tissue suggest that at low strain rates (on the order of 10 −3 s −1 ) the tissue has a Young's modulus of approximately E = 1 kPa, whereas at strain rates of order 1000 s −1 the modulus increases by more than three orders of magnitude to E = 3 MPa [Miller-Young et al 2002;Nightingale et al 2003;Gefen and Haberman 2007;Comley and Fleck 2009]. Comley and Fleck [2011] demonstrates that the stress versus strain behaviour of adipose tissue can be adequately described by a one term Ogden strain energy density function [1972] with a shear modulus µ = E/3 and strain hardening exponent α = 20 of the form…”