There is a relation between mechanics and biology Continuum mechanics is a concept can apply for biological organs like tissue, and describe its macro-mechanical view by equations.

1. BY
(Dina Amin)

2. Content Biomechanics
Continuum Biomechanics
Mechanical Characteristics of Soft Tissues
Modeling tissue mechanics
Usage of Continuum Mechanics for tissues
Poroelasticity
The advantage of continuum descriptions

3.  Biomechanics is the development, extension and
application of the principles and methods of
mechanics for studying problems of biology and
medicine.
 Mechanobiology is the study of biological responses
by cells to mechanical stimuli.

4.  Continuum Biomechanics focuses on cells, tissues and
organs and naturally complements studies in
mechanobiology
 Modern Continuum Biomechanics emerged in the mid-
1960s following advances in nonlinear continuum
mechanics and rapidly grew with advances in
computational methods and computer technology.

5.  Soft tissues have a complex structure that is generally
described as a:
o Nonlinear
o Inelastic
o Heterogeneous
o Anisotropic character
 It varies from point to point, from time to time and
from individual to individual”

6. Modeling
tissue
mechanics
Microscopic
view
From cells to
tissue
Macroscopic
view
Organ
biomechanics

7. 1. This formalism gives a rigorous formulation of
morphogenesis, providing explicit results as a
function of macroscopic quantities, which can be
evaluated experimentally
2. appropriate when mechanics interplays with
processes that translate well into continuous
equations, such as diffusion and transport in the
context of chemotaxis.

9.  The structure of soft tissues is generally considered
biphasic, consisting of a porous solid phase and a fluid
phase.
 Different important functions are attributed to the
fluid constituent in tissues:
1. transport of nutrients from the vascular
system to cells
2. removal of waste from cells
3. preventing friction in cartilage
4. drug delivery and distribution
5. in addition to its role in load transfer

10.  Poroelastic material behavior is similar to that of
viscoelastic materials where it experiences creep under
a constant stress and relaxation under constant strain
steps.

11. There are two scenarios of fluid movement inside the
porous media are considered:
 Drained condition : the pores are assumed to be
connected with each other allowing the fluid to
move out under loading, and therefore the pore
pressure is zero.
 Undrained conditions : the pores are not connected,
and the fluid stays within the pore and contributes to
carrying the pressure exerted by external loading.

12.  the response of porous materials can be considered at
both macromechanical (continuum) and
micromechanical levels.
 The macromechanical describes the over all behavior
of a material without describing the contributions of
individual constituents by using bulk material
properties of
 (K)→ The bulk modulus of drained elastic solid.
 (Ku)→ The undrained bulk modulus.
 (α)→ The Biot’s coefficient respectively.
 The Biot’s coefficient is the ratio of the gained (or
lost) fluid volume of an element to the total volume
change of that element when pore pressure is allowed
to return to its original state.

13.  Biot’s theory assumes a linear relationship between the applied stress
(𝜎𝑖𝑗, p) and strains ( 𝜀𝑖𝑗, ζ), in addition to the elastic assumption (i.e.,
full reversibility of deformation).
𝜀 = −
1
𝐾
(𝑃 − 𝛼𝑝)
𝜁 = −
𝛼
𝐾
𝑃 −
𝑃
𝐵
𝐵 =
𝐾 𝑢 − 𝐾
𝛼𝐾 𝑢
 where:
o P is the total mean isotropic pressure
o p is the pore pressure
o K and Ku are the drained and undrained bulk moduli,
respectively
o ε and ζ are the volumetric strain and fluid content variation,
respectively

14. The advantage of continuum descriptions of growing
tissues is two-fold.
 First, continuum mechanics provides a well
established framework to discuss material behavior
on macroscopic scales, at least for passive materials.
 Second, the formulation of the tissue-mechanics
problem in terms of partial differential equations
allows in principle to derive analytical expressions for
the stress distribution and the cell flow field

15. 1) Biomechanics Of Soft Tissue – Principles and
Application [Adil Al-Mayah].
2) Growth and remodelling of living tissues:
perspectives, challenges and opportunities
[Ambrosi D, Ben Amar M,Cyron CJ, DeSimone A,
Goriely A, Humphrey JD,Kuhl E].
3) Physics of growing biological tissues: the complex
cross-talk between cell activity, growth and
resistance[Ben Amar M, Nassoy P, LeGoff L].
4) Mechanics of Growing Tissues: A Continuum
Description Approach[Jonas M. Ranft].
5) Biomechanics of Soft Tissue [G.A. Holzapfel].
6) Tissue Mechanics [Stephen C. Cowin- Stephen
B.Doty].

16. Thank
You