European Journal of Biomedical and Pharmaceutical Sciences

CELLULAR ELASTICITY (STIFFNESS), PLASTICITY, AND VISCOELASTIC NATURE OF ANIMAL TISSUES INCLUDING BODY FLUIDS- PHYSIOLOGICAL, AND BIOPHYSICAL ASPECTS-I

*Y. K. Lahir

ABSTRACT

All matters possess three main physical features namely, hardness, flexibility and fluidity. These physicomechanical properties are distinctly different in varying degrees in solids, liquids and areal/gaseous form of materials. The hardness exists in decreasing order while flexibility and fluidity are in reverse order. Biological matter has specific shape and size which responds to the external forces applied on them. These features follow the basic mechanics of physical sciences. Biological materials are also behaving in physicomechanical pattern. The physical forces are sensed by biological matters which also exhibit these physicomechanical features. The bones are solid in nature, while other soft tissues represent the flexible matter, such as muscular, connective tissues and tissues made of cells. The body fluids like blood, lymph, cerebrospinal, synovial fluids represent the liquid features present in a biosystems. Cell membrane and other membranous constituents exist in fluid state. All these are made-up of more of less fixed and set molecules which are arranged in specific pattern. The features of elasticity, plasticity and viscoelasticity are among the physicomechanical bases of biological materials also. These biological tissues show very intense relationship with mechanical forces and these forces act as the basis of the mechanophysiological aspects of biological matter. Even the biomolecules which regulate the force-induced functionalities show distinct correlation. The mechanism is broadly accepted but their intricate aspects are still obscure. With advancement in technology, methodology, conformational and physiological dynamics of biological materials is becoming more relevant and helpful in understanding the complexities of physiological aspects of life. These mechanical forces are intricately and inexorably associated with the living being and represent the normal healthy and diseased state. The components of biological matter exhibit a capacity to sense these physical changes occurring under physical forces in precise manner. Their response is time dependent behaviour with qualitative and quantitative degrees of mechanosensing and mechanotransduction manner. These interactions involve the unit cell, cell organelles, cytoskeleton, extracellular matrix, glycocalyx, cell membrane and interstitium. There is a need to understand the complexities of interactions, mechanical regulatory functions of conformational dynamics of each functional unit of cell and the biomolecules interacting in the various biological phenomena. Hence, an effort is made to ponder and delve in this realm of interactions between physical aspects of the biological materials.

Keywords: biomechanics, elasticity, Hooke’s law, loading path Poisson’s ratio, plasticity, viscoelasticity, stress, strain, self-limiting mechanism, unloading path.