Normally the soft tissue is very hydrated because of the ground substance.
The fibroblasts are the most common cell responsible for the production of soft tissues' fibers and ground substance.
Variations of fibroblasts, like chondroblasts, may also produce these substances.
The collagen fibers are comparatively inextensible and are usually loose (wavy, crimped).
With increasing tissue deformation the collagen is gradually stretched in the direction of deformation.
When taut, these fibers produce a strong growth in tissue stiffness.
In soft tissues, the collagen limits the deformation and protects the tissues from injury.
Human soft tissue is highly deformable, and its mechanical properties vary significantly from one person to another.
Impact testing results showed that the stiffness and the damping resistance of a test subject’s tissue are correlated with the mass, velocity, and size of the striking object.
Such properties may be useful for forensics investigation when contusions were induced.
When a solid object impacts a human soft tissue, the energy of the impact will be absorbed by the tissues to reduce the effect of the impact or the pain level; subjects with more soft tissue thickness tended to absorb the impacts with less aversion.
Soft tissues have the potential to undergo large deformations and still return to the initial configuration when unloaded, i.e. they are hyperelastic materials, and their stress-strain curve is nonlinear.
In order to describe the mechanical response of soft tissues, several methods have been used.
These methods include: hyperelastic macroscopic models based on strain energy, mathematical fits where nonlinear constitutive equations are used, and structurally based models where the response of a linear elastic material is modified by its geometric characteristics.
Even though soft tissues have viscoelastic properties, i.e. stress as function of strain rate, it can be approximated by a hyperelastic model after precondition to a load pattern.
After some cycles of loading and unloading the material, the mechanical response becomes independent of strain rate.
Despite the independence of strain rate, preconditioned soft tissues still present hysteresis, so the mechanical response can be modeled as hyperelastic with different material constants at loading and unloading.
By this method the elasticity theory is used to model an inelastic material.
Fung has called this model as pseudoelastic to point out that the material is not truly elastic.
This retraction usually causes a visual artifact.
where a, b and c are constants.
Simplification for small and big stretches
For small strains, the exponential term is very small, thus negligible.
On the other hand, the linear term is negligible when the analysis rely only on big strains.
Further information: Gent (hyperelastic model)
Remodeling and growth
Soft tissues have the potential to grow and remodel reacting to chemical and mechanical long term changes.
The rate the fibroblasts produce tropocollagen is proportional to these stimuli.
Diseases, injuries and changes in the level of mechanical load may induce remodeling.
An example of this phenomenon is the thickening of farmer's hands.
Mechanobiology is the science that study the relation between stress and growth at cellular level.
There are certain issues that have to be kept in mind when choosing an imaging technique for visualizing soft tissue extracellular matrix (ECM) components.
The accuracy of the image analysis relies on the properties and the quality of the raw data and, therefore, the choice of the imaging technique must be based upon issues such as:
- Having an optimal resolution for the components of interest;
- Achieving high contrast of those components;
- Keeping the artifact count low;
- Having the option of volume data acquisition;
- Keeping the data volume low;
- Establishing an easy and reproducible setup for tissue analysis.
The collagen fibers are approximately 1-2 μm thick.
Thus, the resolution of the imaging technique needs to be approximately 0.5 μm.
Some techniques allow the direct acquisition of volume data while other need the slicing of the specimen.
In both cases, the volume that is extracted must be able to follow the fiber bundles across the volume.
High contrast makes segmentation easier, especially when color information is available.
In addition, the need for fixation must also be addressed.
It has been shown that soft tissue fixation in formalin causes shrinkage, altering the structure of the original tissue.
Imaging methods used in ECM visualization and their properties.
|Transmission Light||Confocal||Multi-Photon Excitation Fluorescence||Second Harmonic Generation||Optical coherence tomography|
|Resolution||0.25 μm||Axial: 0.25-0.5 μm
Lateral: 1 μm
|Axial: 0.5 μm
Lateral: 1 μm
|Axial: 0.5 μm
Lateral: 1 μm
|Axial: 3-15 μm
Lateral: 1-15 μm
|Penetration||N/A||10 μm-300 μm||100-1000 μm||100-1000 μm||Up to 2–3 mm|
|Image stack cost||High||Low||Low||Low||Low|
|Fixation||Required||Required||Not required||Not required||Not required|
|Embedding||Required||Required||Not required||Not required||Not required|
|Staining||Required||Not required||Not required||Not required||Not required|
|Cost||Low||Moderate to high||High||High||Moderate|
Soft tissue disorders are medical conditions affecting soft tissue.
Often soft tissue injuries are some of the most chronically painful and difficult to treat because it is very difficult to see what is going on under the skin with the soft connective tissues, fascia, joints, muscles and tendons.
Musculoskeletal specialists, manual therapists and neuromuscular physiologists and neurologists specialize in treating injuries and ailments in the soft tissue areas of the body.
These specialized clinicians often develop innovative ways to manipulate the soft tissue to speed natural healing and relieve the mysterious pain that often accompanies soft tissue injuries.
This area of expertise has become known as soft tissue therapy and is rapidly expanding as the technology continues to improve the ability of these specialists to identify problem areas more quickly.
A promising new method of treating wounds and soft tissue injuries is via platelet growth factor (PGF).
There is a close overlap between the term "soft tissue disorder" and rheumatism.
Sometimes the term "soft tissue rheumatic disorders" is used to describe these conditions.
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Soft tissue.