Viscoelasticity tissues

The posture and movement in a human body is powered by muscles. There are more than 600 muscles in the human body. Muscles are connected to the skeleton via tendons, which are composed of strands of collagen tissues (viscoelastic tissue) that allow more stretching compared to the ligaments and are attached to the periosteum of the bone on one end and to the muscle in series at the other end. The connection to the muscles comprises the Golgi tendon organs that signal information about stretching and its rate to the central nervous system. 

Hyaluronic acid is a linear polysaccharide found in the highest concentrations in soft connective tissues where it fills an important structural role in the organization of the extracellular matrix (23,24). It has been used in ophthalmic preparations to enhance ocular absorption of timolol, a beta blocker used for the treatment of glaucoma (25), and in a viscoelastic tear formulation for conjunctivitis (26). The covalent binding of adriamycin and daunomycin to sodium hy-aluronate to produce water-soluble conjugates was recently reported (27). 

The vitreous is a transparent extracellular matrix occupying the space between the posterior lens and the retina and, in the majority of vertebrate species, constitutes the major f)art of the volume of the eye. Embryo-logically it can be considered as the basement membrane of the retina. It provides a mechanical support for surrounding tissues and acts as a shock absorber by virtue of its viscoelastic properties (Balzas and Delinger, 1984). Vitreous consists mainly of water (98%) and colloids (0.1%) with ions and low molecular weight solutes making up the remainder. It is not fully developed at birth, and changes in both volume and chemical composition occur postnatally. 

Chondroitin sulfate (Viscoat , DuoVisc ) is also used in combination with sodium hyaluronate as a viscoelastic surgical aid to provide higher viscosities, which may provide additional tissue protection... 

Fig. 9. Viscoelastic properties of ultrasound-treated ex vivo porcine muscle specimen. Muscle samples were coagulated with focused ultrasounds in selected regions. MRE using the method of Ref. 23 was carried out and shear moduli were calculated in normal and heated regions at different shear wave frequencies. Upper curve FUS-treated tissue. Lower curve normal tissue. Error bars are for standard deviations. (From Ref 47, reprinted by permission of Wiley-Liss, Inc., a subsidiary of John Wiley Sons, Inc.)...

Alvarez, M. D., Canet, W., Cuesta, R, Lamua, M. (1998). Viscoelastic characterization of solid foods from creep compliance data application to potato tissues. Z Lebensm. Unters. Forsch. A., 207, 356-362. 

Barrier must be flexible (viscoelastic) as tissue to prevent fracture leading to disbanding from tissue... 

The physical properties of barrier dressings were evaluated using the Seiko Model DMS 210 Dynamic Mechanical Analyzer Instrument (see Fig. 2.45). Referring to Fig. 2.46, dynamic mechanical analysis consists of oscillating (1 Hz) tensile force of a material in an environmentally (37°C) controlled chamber (see Fig. 2.47) to measure loss modulus (E") and stored modulus (E ). Many materials including polymers and tissue are viscoelastic, meaning that they deform (stretch or pull) with applied force and return to their original shape with time. The effect is a function of the viscous property (E") within the material that resists deformation and the elastic property (E )... 

LARGE STRAIN ANALYSIS OF 3-D VISCOELASTIC SWELLING OF CHARGED TISSUES AND GELS... 

Abstract Materials like soft biological tissues undergo large viscoelastic deformations... 

Chondrocytes respond biologically to mechanical stimuli, and this is called mechanotransduction. Understanding cellular responses to mechanical stimuli and how they can be related to tissue level characteristics has many applications in biology, tissue engineering and medical science. Information about the mechanical properties of chondrocytes is fundamental to such research. Micropipette aspiration has been applied to investigate the deformation of single chondrocytes (Jones et al., 1999). It was found that human chondrocytes behave like viscoelastic solids. The Young s modulus of normal chondrocytes appeared to be very variable, but was of the order of 0.65 + 0.63 kPa. However, the viscoelastic behaviour was not quantified. 

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