This presentation details about structure, function, material properties and modelling of various soft tissue in our bodies.

1. SOFT TISSUE
140280103050-Sakhiya Chirag
140280103051-Saksena Dhruv
140280103052-Sanghadia Mittal
140280103053-Shah Krupa
140280103054-Shah Pankti
140280103055-Shah Shreya
140280103056- Singh Jyoti
140280103057-Taraviya Rakshit
140280103058-Trivedi Nishit
140280103059-Unwala Mariam

2. Introduction
• Soft tissue is found all over the body. It includes tissues that connect,
support or surround other structures and organs in the body. Types of
soft tissue include:
 Cartilage
 Tendons
 Liagments
 Muscle

3. Cartilage- Structure
Flexible connective tissue
Avascular (no blood supply hence slow
healing)
Made up of three basic structure: matrix,
chondrocyte and fibres( collagen and
elastic)

4. Cartilage-Structure
• Chondroblast –
produces matrix
• Matrix- composed of
collagen and elastic
fibres with ground
substance
• Chondrocyte-
chondroblast embedded
in matrix
• Lacunae- spaces
surrounding one or
more chondrocyte
• Perichondrium:
membrane surrounding
the cartilage to receive
blood and nerve supply

5. Cartilage- Function
 load bearing
 Lubricin, a glycoprotein abundant in cartilage
and synovial fluid, plays a major role in bio-
lubrication and wear protection of cartilage
Flexiblity
Shapes the structure

6. Cartilage- Modelling
 Under compression, the negatively charged sites on
aggrecan are pushed closer together, which increases
their mutual repulsive force and adds to the
compressive stiffness of the cartilage
 When deformed, fluid flows through the cartilage
and across the articular surface.
 Recognizing that fluid flow and deformation are
interdependent has led to the modelling of cartilage
as a mixture of fluid and solid components- Biphasic
model of Cartilage

7. Cartilage- Modelling
 In this modelling, all of the solid like components of the
cartilage, proteoglycans, collagen, cells, and lipids are
lumped together to constitute the solid phase of the
mixture.
 The interstitial fluid that is free to move through the
matrix constitutes the fluid phase.
 Typically, the solid phase is modelled as an
incompressible elastic material, and the fluid phase is
modelled as incompressible and inviscid, that is, it has
no viscosity .
 Under impact loads, cartilage behaves as a single-phase,
incompressible, elastic solid; there simply isn’t time for
the fluid to flow relative to the solid matrix under
rapidly applied loads.

8. Cartilage- Material Properties
Using an indentation test, cartilage is tested in
situ. Since discs of
cartilage are not removed from underlying
bone, indentation may be used to test
cartilage from small joints.
Three independent material properties are
obtained from one indentation test.
Typically, an indentation test is performed
under a constant load.

10. Cartilage- Material Properties
 Displacement of the
cartilage is a function of
time, since the fluid
cannot escape from the
matrix instantaneously
 The diameter of the
indenter varies
depending on the
curvature of the joint
surface, but generally is
no smaller than 0.8 mm.

11. Cartilage- Material Properties
 Fitting the biphasic model of the test to the measured indentation,three
properties are determined .
 Poisson’s ratio- is typically less than 0.4 and often approaches zero.
 When cartilage is loaded, fluid flows out of the solid matrix, which
reduces the volume of the whole cartilage.
 Cartilage is mixture of solid and liquid which makes the whole tissue
compressible although the components are incompressible .
 Aggregate modulus - its a measure of the stiffness of the tissue at
equilibrium when all fluid flow has ceased.
 The higher the aggregate modulus, the less the tissue deforms under a
given load.
 The aggregate modulus of cartilage is typically in the range of 0.5 to
0.9 MPa .
 Cartilage has a much lower stiffness (modulus) than most engineering
materials.

12. Cartilage- Material Properties
 Permeability- indicates the resistance to fluid flow
through the cartilage matrix.
 Permeability of cartilage is typically in the range of 1015
to 1016 m4 /Ns.
 Permeability is not constant through the tissue.
 Permeability highest- near the joint surface -making
fluid flow relatively easy- equilibrium reached quickly
 lowest- deep zone-making fluid flow relatively difficult-
equilibrium reached gradually .
 These qualitative results are helpful for interpreting data
from tests of normal and osteoarthritic cartilage.

13. Cartilage- Material Properties

14. Cartilage- Material Properties

15. Tendons and ligaments-Structure
Tendons and ligaments are very similar in
structure and composition.
 They are both composed of collagen and
elastin fibers, with a structural hierarchy.
 Structurally, tendons connect muscle to
bone, and ligaments connect bone to bone.

16. Tendons and ligaments-Structure

17. Tendons and Ligaments- Functions
• Functions of Ligaments-
Transmit load from bone to bone
 Hold the skeleton together
Provide stability at joints
Limit freedom of movement
Prevent excessive motion by being a static
restraint

18. Tendons and Ligaments- Functions
• Functions of Tendons:
Attach muscle to bone
Transmit tensile loads
Position of muscle relative to joint

19. Tendons and Ligaments-Material
Properties:
 The material composition and properties of tendons
and ligaments reflect the differences in loading that
they will commonly experience.
 As tendons will transmit significant forces from the
muscle into movement of the bone very regularly,
they are a slightly stronger tissue than ligaments,
and are composed of more collagen fibers (roughly
85% versus 70%).

20. Tendons and Ligaments- Material
Properties
 Tensile loading test is done in which continuous measurements
of the load and deflection until failure of the specimen.
 The measured loads and deflections will be normalized by initial
cross-sectional area and length, respectively.
 These normalized quantities are referred to as normal stress and
strain.
 Typical engineering materials (e.g. steel and aluminum) usually
exhibit linear, elastic, homogeneous, and isotropic properties,
which is reflected in a linear stress-strain curve for loads below
the elastic limit
 In contrast, biological materials often exhibit non-linear,
inelastic, non-homogenous and anisotropic behavior.

22. Tendons and Ligaments-
Material Properties
 In the tendon, the fibrils are composed
of many crimped collagen fibers, and
many fibrils are adhered to each other.
 When the tissue is stretched, the fibers
uncrimp and straighten, which
contributes to the toe region of the curve.
 As load is increased, continuously
increasing amounts of fibers are
recruited.
 Finally, in the linear portion of the stress
– strain curve, all fibers have been
recruited and are straight.
 A linearly increasing stress versus strain
response is then exhibited.
 At larger strains, the tendon will begin to
undergo micro-damage, leading to the
eventual macro-damage and failure.

23. Tendons and Ligaments- Material
Properties
 Biological materials also exhibit viscoelastic behavior.
 The viscoelastic behavior is time dependent aspect of the material
response.
 The viscoelastic behavior of biological materials is due various
interactions of collagen with the proteins, water, and ground
substance when it is loaded.
 As this is a rate dependent phenomenon, a material will respond
differently if loaded quickly as opposed to loading more slowly.
 The slope of the stress – strain curve will increase with an increasing
strain rate, and the apparent elastic modulus, the constant of
proportionality relating the strain to the stress, will increase
accordingly.

24. Tendons and Ligaments- Material
Properties
• If a viscoelastic material is stretched to a
constant deformation, it will slowly relax,
with the stress in the material decreasing. A
relaxation curve is a plot of the viscoelastic
stress versus time response.

25. Tendons and Ligaments- Modelling
The three most common models combining
these elements:
A)Voight
B)Maxwell
C)Kelvin

26. Tendons and Ligaments- Modelling
 Under constant strain, the tendon exhibits stress relaxation.
 This means that the stress will decrease (relax) with time.
 The predicted stress relaxation response of these three models is
shown below.

27. Muscles- Structure
The functional unit that produces motion at a
joint consists of two discrete units, the muscle
belly and the tendon that binds the muscle
belly to the bone.
The muscle belly consists of the muscle cells, or
fibers, that produce the contraction and the
connective tissue encasing the muscle fibers.

29. Muscles- Function
 Movement of body
 Maintenance of posture and body position.
 Movement of substances inside the body. The cardiac and visceral
muscles are primarily responsible for transporting substances like
blood or food from one part of the body to another.
 Generation of body heat. As a result of the high metabolic rate of
contracting muscle, our muscular system produces a great deal of
waste heat. Many small muscle contractions within the body
produce our natural body heat. When we exert ourselves more than
normal, the extra muscle contractions lead to a rise in body
temperature and eventually to sweating.

30. Muscles- Material Properties
The force and torque developed by a muscle is
dependent on many factors, including
1. the number of motor units within the muscle,
2. the number of motor units recruited,
3. the manner in which the muscle changes its
length,
4. the velocity of muscle contraction, and
5. the length of the lever arm of the muscle
force.

31. Muscle- Material Properties
Effect of length on force development
The net tensile force in a muscle is
dependent on the force–length
characteristics of both the active and
passive components of the muscle.
A typical tension versus muscle length
diagram is shown

32. Muscle- Material Properties
 The number of cross-bridges between the filaments is maximum,
and therefore, the active tension (Ta) is maximum at the resting
length (lo) of the muscle.
 As the muscle lengthens, the filaments are pulled apart, the
number of cross-bridges is reduced and the active tension is
decreased.
 At full length, there are no cross-bridges and the active tension
reduces to zero.
 As the muscle shortens, the cross-bridges overlap and the active
tension is again reduced.
 When the muscle is at its resting length or less, the passive
(connective) component of the muscle is in a loose state with no
tension.

33. Muscles- Material Properties
Effect of velocity on force
development
 Force is greater during
lengthening than shortening
contraction
 the greater the shortening
velocity (v), the smaller the
force
 Maximum power occurs at
approximately one-third of
maximum velocity and at
approximately one-third of
maximum concentric force.

34. Muscles- Hill’s Muscle Model
Hill assumed:
(1) for a given length, muscle always
develops the same peak force T0(x1,t);
(2) if the muscle is shortening, some force
is dissipated in overcoming inherent
viscous resistance
(3) B: muscle damping constant, which
must be a nonlinear function of
shortening velocity and temperature
(4) KSE: stiffness of the series elastic
component; represents forcedeflection
properties of tendon
(5) KPE: stiffness of the parallel elastic
component; represents forcedeflection
properties of sarcolemma, epimysium,
perimysium, and endomysium

35. Quick Release Experiment
• for determining the Hill
model parameters
• hold muscle length fixed
with the catch
• stimulate muscle to
produce peak (isometric)
force T0
• instantly release catch
• at the instant of release,
muscle force is reduced to
a value T (where T < T0)
that depends on weight in
pan

36. • there is an instant change
(Δx2) in the length of KSE
following release
• this is followed by a more
gradual change (Δx1) in the
length of the muscle
• as T increases, there is a
decrease in v (slope of
dashed line), reflecting that
muscle cannot shorten
quickly under high loads
• combinations of T and v
reflect the force-velocity
properties of a given muscle

37. References
1) http://www.cancer.ca/en/cancer-information/cancer-type/soft-tissue-
sarcoma/soft-tissue-sarcoma/the-soft-tissues-of-the-body
2) Mansour, J. M., Jul 5 2013 Kinesiology: The Mechanics and Pathomechanics
of Human Movement: Second Edition. Wolters Kluwer Health, p. 69-83 15 p.
3) Oatis Carlos Kinesiology: The Mechanics and Pathomechanics of Human
Movement: Second Edition.
4) Supplementary documents for “Computational Neurobiology of Reaching
and Pointing”, by R. Shadmehr and S. P. Wise.
5) N. Ozkaya et al., Fundamentals of Biomechanics: Equilibrium, Motion, and
Deformation,DOI 10.1007/978-1-4614-1150-5_15, # Springer
Science+Business Media, LLC 2012
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Application
7) Stephen Robonovitch Muscle Mecchanics, 2006