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I am Gopi Menon, and I have
been involved in research
on skin barrier for over 25 years.
And it's indeed a
privilege and an honor
to be presenting this topic for
the Henry Stewart series of talks.
Let us start with why barrier
is so important and interesting.
The outermost layer of
skin-- stratum corneum--
is impermeable to water.
It prevents efflux and influx
of water to and from the body.
This barrier allows survival in the
dessicating environment on land,
while still allowing
Unlike the other successful
like the insects, which have a rigid
cuticle coated with hydrocarbons,
mammals developed and evolved a
flexible and highly responsive
barrier, based on a protein
lipid composite structure.
The formation and
maintenance of this barrier
is regulated by a multitude of
internal and external factors,
and many aspects of these are still
being discovered, even as we speak.
Usually, skin talks start
with the largest-organ cliche,
but, as this assumption has
been contested recently,
I would say it is perhaps
the most important organ
and hope that the rest
of the presentation
will justify that view.
Let me briefly outline the various
layers of skin and the epidermis.
Skin is formed of several cell
types and has four compartments.
The outermost epidermis,
the basement membrane,
the dermis-- that has papillary and
reticular layers-- and hypodermis,
which is predominantly
Epidermis is anchored
to the basement membrane
and is composed of keratinocytes,
which make up about 95%
of epidermis; the rest is
melanocytes and dendritic cells,
or Langerhans cells.
The basal epidermal cells
proliferate and differentiate
progressively, moving up
into the spinous, granular,
and cornified layers, in that
order, and cornified cells make up
the outermost stratum corneum layer.