EPIDERMIS/DERMIS/HYPODERMIS
Integumentary System
THE EPIDERMIS

Epidermis: composed of 5 zones or layers called
_STRATA_.



From the inside out these are called: Stratum _BASALE_,
_SPINOSUM_, _GRANULOSUM_, __LUCIDUM_,
and _CORNEUM_.
“Basic
Skin Gets Lots of Care”
THE EPIDERMIS

Like all epithelial tissues the epidermis is _AVASCULAR_.

Most of the cells are _KERATINOCYTES_ (keratin cells)
which produce _KERATIN_ that makes the epidermis a tough
protective layer.
THE EPIDERMIS

The deepest layer is called the stratum _BASALE_.

These cells are constantly undergoing cell _DIVISION_.

Millions of new cells are produced daily. These cells push
up away from the dermis and up to the more
_SUPERFICIAL_ layers of the epidermis.
THE EPIDERMIS

The next layer is the stratum _SPINOSUM_ and then the
stratum _GRANULOSUM_.

Then the cells become _FLATTER_, increasingly full of
_KERATIN_ and finally _DIE_.

This then forms the next layer, the stratum _LUCIDUM_,
which is clear and found only where the skin is _HAIRLESS_
and extra thick. (Palms of hands and soles of feet).
THE EPIDERMIS

The outermost layer, the stratum _CORNEUM_ is _20_ to
_30_ cell layers thick and accounts for about three-quarters of
the epidermal thickness.

This layer is filled with _KERATIN_ to provide us with an
“overcoat” for the body. This layer rubs and flakes off slowly
and steadily.

It is replaced with the basale cells so we have a totally new
epidermis every _25_ to _45_ days.
THE DERMIS

The dermis is your “hide.” It is a strong, stretchy
envelope that is composed of _DENSE_ _CONNECTIVE_
tissue. The dermis consists of 2 major regions:
(1)
_PAPILLARY_ layer and
(2)
the _RETICULAR_ layer.
THE DERMIS

The _PAPILLARY_ layer is the upper layer.

It has uneven _FINGERLIKE_ projections from its
superior surface called dermal _PAPILLAE_ which indents
the epidermis above.

Many of these contain _CAPILLARY_ loops which
furnish _NUTRIENTS_ to the epidermis.
THE DERMIS

Others house _PAIN_ receptors and touch receptors
called _MEISSNER’S_ _CORPUSLCES_.

The ridges that are formed complete the
_FINGERPRINTS_ that are used to identify us.
THE DERMIS


The _RETICULAR_ layer is the _DEEPEST_ skin layer.
This area contains the following: _BLOOD_
_VESSELS_,

_SWEAT_ and _OIL_ _GLANDS_,

and deep pressure receptors called _PACINIAN_
_CORPUSCLES_.

Here are many _PHAGOCYTES_ that act as another
protective barrier if bacteria gets through.
THE DERMIS

Both _COLLAGEN_ and _ELASTIC_ fibers are found to
allow for the toughness of the dermis.

The dermis is abundantly supplied with _BLOOD_ vessels
that are vital in body temperature _HOMEOSTASIS_.

The dermis also has a rich _NERVE_ supply. These nerve
endings have specialized receptor-end organs that send
messages to the CNS for interpretation.

Examples include: _PRESSURE_ and _TEMPERATURE_.