Medical & Clinical Research

Author(s): Janos Vincze, Gabriella Vincze-Tiszay

The transport phenomena mean the variation in time and space of generalized forces when they generate flows for which conservation laws apply. According to the general definition, the diffusion is a mass transportation under the action of a generalising force, which can be the concentration gradient, the pressure gradient, etc. The diffusion is explained on the basis of the spontaneous movement of the molecules which have the tendency to spread in equal numbers in each subspace tendency which arises from the concentration gradient. The diffusion is a frequently found phenomenon: with diffusion, the respiratory gas exchange takes place between the air in the alveoli, blood and cellular cytoplasm, the nutritive substances diffuse from the thin intestine into blood and further away in the tissues, the diffusion lays at the basis of the white cells’ chemotactism, the olfaction happens when the molecules of the smelling substances spread in the air reach the cells of the olfactory mucosa. A particular case of diffusion is dialysis, which consists in the diffusion thought semipermeable membranes of the substances with a molecule smaller than the membranes pores. The dialysis takes place up to the equalising of the concentration in the two parts of the membrane.