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Lifestyle Chemistry
Part 3: Skin
Identify the role of 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 diseasecausing organisms
Skin Vocabulary
Skin Vocabulary
define the term ‘microflora’ and discuss the
role of the microflora
on skin in different parts of the body
What is microflora?
• microflora is defined as microorganisms surviving as
microscopic communities.
• Most microflora on and in the body are bacteria.
More Vocabulary!!
• Bacteria: single-celled procaryotic organisms belonging to the protist
kingdom.
• Staphylococci: cocci bacteria appearing in grape-like formations.
• Cocci: sphere-shaped bacteria.
• Microbes: micro-organisms.
• Micro-organisms: microscopic, often single-celled, organisms.
• Sebum: oil produced by sebaceous glands in the dermis.
• Epidermis: outermost layer of the skin which protects the underlying
tissue, forms a barrier from heat loss, water loss and micro-organisms.
• Keratin: tough protein present in the epidermis of vertebrate organisms.
Microflora and Skin
• Micro-organisms prefer moist environments.
• Nutrients available for microflora:
• Sweat from sweat glands contains sodium chloride and
lactate.
• Sebum, an oily substance from sebaceous glands next to
hair follicles.
Microflora and Skin
Why does microflora not
colonise?
• The skin surface is constantly
losing clumps of dead skin.
Any microbes on the skin
surface are lost. The pH of
skin is slightly acidic – at 5.5
pH. Most microbes prefer a
pH neutral environment of 7.
For these reasons, only
specific microbes are able to
survive on the skin surface.
Microflora and Skin
• The action of microflora on the skin causes the oil on
the skin to become acidic. Microbial action on sebum
releases smelly gases, commonly referred to as body
odour.
Bacteria
Moulds
Explain the difference between moulds and bacteria when
viewed under a microscope.
Types of Microflora
Resident microflora
• Found on the skin surface and are thought to reside
in the sebaceous glands under the skin.
• Bacterial counts are higher where more oil is being
produced by sebaceous gland activity.
• Thought to play an important role in protecting the
individual from more pathogenic or disease-causing
bacteria. The body is protected from skin diseases
and disorders by the microbes living on the skin
surface.
Types of Microflora
Transient microflora
• The first source is the external environment eg. soil,
water and air. Contact with soil, water and air
transfers any microbes present to the skin surface.
• The second source is the natural microflora that
comes out of body orifices such as the nasal
passages, ear canals and anus. Micro-organisms are
transferred to various parts of the body by the hands.
• Transient microbes can cause diseases such as
diarrhoea and meningitis.
discuss the term pH in terms of its
ability to describe the acidity of
a substance
pH Scale
Explain the relationship between the natural
pH of the skin and the action of
• Microflora
• Natural oil produced by glands in the skin
• Perspiration
pH and the Skin
• The natural pH of the skin is slightly
acidic, with a pH range of 4.5 to 6.
pH and the Skin
Factors that make our skin slightly acidic:
• Sebum has a slightly acidic pH
• Perspiration:
Sweat produced by heat is more acidic
than sweat in response to exercise.
Identify and explain the use of common
components of body soaps, cleaners and
shampoos and the reason for their use.
Skin Soaps
• Soap coats the skin in grease-removing chemicals.
• They consist of a hydrocarbon chain which is
repelled by water but attracted to oil, grease and
dirt.
Cleansers
• Common components include mineral oil, water
and a stearate.
• Contain a moisture absorber
• Dissolve Sebum and loosen particles of grime and
dirt.
Shampoos
• Extra chemicals in shampoo make the lather
stay in the hair and remove grease.
• The detergent in shampoo emulsifies the
sebum into the water to be washed away.