Transcript The Skin - Bwattleseniorscience

The Skin
Identify the role of the skin
-an organ to separate the body
from the external environment
• The skin is an organ to separate the body
from the external environment. The
epidermis forms an effective barrier to
separate the rest of the body from the
external environment.
• The stratum corneum, which forms part
of the epidermis, consists of the dead skin
cells that have died from lack of food and
oxygen. These dead cells are firmly
attached to one another and are
keratinised.
• They protect the living cells beneath them
and help reduce water loss. The dead
cells flake away and form most of the dust
that collects in our houses.
House dust and a dust mite
It has been calculated
that the average person
sheds about half a
kilogram of skin a year,
an organ assisting in body
temperature control
• The skin is an organ assisting body
temperature control. Sweat glands, found
in the dermis, produce a liquid that is
released through the pores in the
epidermis.
A sweat gland.
• When this liquid is released on the surface
of the body it evaporates and this in turn
cools the body surface. When the body
becomes hot, the rate at which these
glands produce sweat or perspiration
increases.
Sweat Glands
Evaporative Cooling
• As well as this, when the body becomes
hot, the blood vessels dilate, which
allows loss of heat through the epidermis.
These processes help to maintain the
body temperature at 37oC
Dilated Blood Vessels
an organ to protect against entry
by disease causing organisms
• The skin protects our body against
disease in a number of ways:
• The shedding of the top layer of skin (the
stratum corneum) helps prevent the entry
of disease causing organisms.
• The film on the surface of our skin, that
contains a mixture of sweat, sebum and
microflora, is acidic. The acidity comes
from the fatty acids that are present in the
sebum and from the acids present in
sweat.
Cultured Skin Microflora
•
The acidity is increased by the presence
of Staphylococcus epidermis, bacterial
microflora that break down the fatty acids
in the sebum. Many other bacteria
cannot survive in such an acidic
environment.
• The high concentration of salt in sweat
creates an environment that is
inhospitable to many bacteria.
• The presence of skin microflora holds in check
the small number of pathogenic organisms that
are on our skin surfaces.
• Different parts of the body have different
populations of microflora, in balance with the
small number of pathogens. This balance can be
disturbed by variations in the diet, the use of
antibiotics, the use of personal hygiene products
and by physical injury.
Define the term ‘microflora’ and
discuss the role of the microflora
on skin in different parts of the
body
• Microflora are microorganisms, including
bacteria, fungi, algae, protozoa and
viruses, that live in harmless association
with our skin. They are able to survive the
acidic nature of our skin and sometimes
actually help us against the entry of
pathogens.
Microorganisms that cause disease are
referred to as pathogens. The presence of
the microflora limits the resources
available for pathogenic bacteria that may
be able to survive the acidic, salty
environment.
• The microflora also increase the acidic
nature of the skin therefore making it even
more inhospitable to many pathogens.
• The number and type of microflora found
on the skin varies in different parts of the
body and between different individuals.
The population of microflora of an
individual is established soon after birth.
• Some of the microflora that are harmless
on the surface of the skin can become
quite dangerous if the skin surface is
broken and they are able to enter the
bloodstream. Staphylococcus aureus
can cause serious disease if it gains entry
to the bloodstream during medical
procedures. Its presence is a serious
problem for hospitals and surgeries.
• One species of microflora,
Corynebacterium acnes, live in the hair
follicles, usually without harm to a person.
However, when the dead skin from the
epidermis occasionally blocks a
sebaceous gland of a hair follicle, the
bacteria may infect surrounding tissue
resulting in inflammation and causing a
pimple.
Discuss the term pH in terms
of its ability to
describe the acidity of a
substance.
• The pH scale can be used very effectively to describe the
degree of acidity of a substance. The pH scale
commonly has the range of 0-14, where a pH of 7 is
regarded as neutral. Substances with a pH below 7 are
regarded as acidic and substances with a pH above 7 are
regarded as alkaline. Indicators such as litmus paper,
universal indicator paper or universal indicator solution,
methyl orange or phenolphthalein can be used to
determine the pH of a substance. Alternatively pH meters
or probes can be used to determine the pH electronically
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 oil in the skin is produced by
sebaceous glands and is slightly acidic.
• The sweat or perspiration on our skin is
produced by the sweat glands and is also
slightly acidic.
• Most bacteria can survive in a narrow pH
range. The bacterial microflora on our skin
are able to survive acidic conditions with a
pH range 4-6. Other harmful bacteria
cannot usually survive this environment
and so our acidic skin protects us from
harmful bacteria or pathogens.
• Some of our microflora are able to
breakdown the fatty acid molecules (from
the natural oils) in our skin and thereby
increase its acidity.