Mechanical properties of skin and exploration methods

Its thickness ranges between a few tenths of millimeters and 5-6 mm for areas submitted to high stresses and loads such as the soles of the feet. This organ (encompassing cells, fibres, sebaceous and sweat glands, hairs, nerves, blood vessels) ensures numerous essential functions such as maintaining homeostasis and protecting the organism from external aggressions (mechanical, thermal, chemical, bacterial, etc.) It is sometimes said that it is the silence of organs that defines their health. This is probably why we almost forget the mechanical function of the skin. This is unfair when we consider its incredible ability to absorb shocks, to support all internal body tissues, to stretch so as to allow movements, changes of posture and variations of body volume in the case of pregnancy for instance. This article aims to bring light to this critical mechanical function and to present the different methods which can be used for its exploration and measurement. 

Structure of the skin

Human skin is a complex multilayered organ. The outermost layer is the epidermis. Deeper are found the dermis and the hypodermis (Fig 1). Each layer is characterised by different functions and structures and the thickness of each of which depends on age, gender and anatomical location. A full description of the structure and functions of the skin is out of scope of this short article. We will simply give a brief overview while emphasising the facts which are important for the understanding of the mechanical behaviour of the skin.