9.2 Lifestyle Chemistry: Skin and Microflora

Revision

1. State one example of oil-in-water and one example of water-in-oil emulsions
2. Describe four different types of emulsions
3. Explain why cleaning agents must be surfactants

Objectives

•       identify the role of the skin as

                – an organ to separate the body from the  external environment

                – an organ assisting in body temperature control

                – an organ to protect against entry by    disease-causing organisms

•       define the term ‘microflora’ and discuss the role of the microflora on skin in different parts of the body

•       discuss the term pH in terms of its ability to describe the acidity of a substance

•       explain the relationship between the natural pH of the skin and the action of

                – microflora

                – natural oil produced by glands in the skin

                – perspiration

•       identify and explain the use of common components of body soaps, cleansers and shampoos and the reason for their use

The skin

•       The skin performs a number of roles

–      Protects from the outside environment, especially dangerous organisms

–      Allows enough sunlight through for vitamin D but not enough to do damage (ideally)

–      Sense temperature and pressure changes

–      Temperature control

–      Excretes water, urea and minerals (sweat)

•       The skin is made up of two layers, the epidermis (outer layer) and the dermis (inner layer).  Below that is the hyperdermis.

•       Describe the process by which skin increases the body’s temperature

•       Describe the process by which the skin decreases the body’s temperature

•       Practical investigation:

•       Using a microscope/bioviewer to view skin samples

•       Draw what you observe

Microflora

•       Microflora refers to the full range of microorganisms and they live, amongst other places, on your skin and in your body.

•       The skin is a barrier to most microflora because it is:

–      Too acidic

–      Too cold

–      Too salty

–      Exposed to UV radiation

–      Too dry (in parts)

•       Microflora make it harder for pathogens to survive on the skin.  They take up space and consume food.

Types of Microflora

•       Bacteria:

–      Cocci (skin surface, usually harmless)

–      Diptheroids (follicles, can cause pimples)

•       Yeast (fungi):

–      Pityrosporum ovale  (eats fat, can cause dandruff)

–      Malassezia furfur (chest and back)

–      Candida albicans (can cause thrush)

–      Trichospora beigelii (scalp)

•       Mites:

–      Democlex folliculorum (hair follicles, harmless)

Components of body soaps, cleansers and shampoos

•       Soap

–      Fatty acids or sodium

•       Cleansers

–      Surfactants, humectants, perfumes, preservatives, antioxidants, acidifying agents, bactericides

•       Shampoo

–      Detergent, surfactants, pH balances, germicides, perfumes, colouring agents

Review questions

1. State the function of human skin
2. Describe the different parts of human skin
3. Explain why cosmetics should be pH neutral.
4. Explain why cosmetics could not be perfectly pH neutral