Difusão através da pele- inglês

Dermal Diffusion

Roberta Alves Medina

Transport Phenomena II

Introduction
This work will discuss some aspects of mass transfer through the skin and factors which may enhance or reduce it. By Studying the penetration of substances through the human tissue is possible to measure the efficiency of medications, cosmetics and also determine the exposition limits for hazardous substances. In 1904 Schwenkenbecher concluded from his experiments that the skin is more permeable to lipid soluble substances and gases and is practically impermeable to electrolytes and water.[5] The fast advance of sensitive analytical techniques in the latest 50 years has enabled researchers investigate the passage of substances into, and throughout, the skin and know more about the factors which may inhibit or increase this phenomena. Skin is the biggest organ in the human body. It acts as a barrier to protect the body of losing moisture or heat and is a semi permeable membrane protecting the body against harmful external agents. The skin is divided into three main parts as shown in figure 1 [7]. These three parts are the stratum corneum which is the most protective layer therefore has the lower diffusion coefficient . This layer is filled with keratin which gives the skin strength and mechanical resistance. The internal layers, the epidermis and dermis are more penetrable having bigger diffusion coefficient. Sweat glands, sebaceous glands and hair follicles are part of this complex system.

Figure 1: Simplified representation of skin showing routes of penetration: 1. through the sweat ducts; 2. directly across the stratum corneum; 3. via the hair follicles.

Summary of literature findings
Studying the effect of diffusion throughout the skin is important because some active ingredients in cosmetics or in medicines may be absorbed through the skin. By using topical medicines you may avoid some side effects that could occur in case of you ingest the drug, including damages to