The dermis houses many different structures that allow the skin to
function effectively.

Sweat Glands
The sweat glands, which are sometimes referred to as the sudoriferous
glands, extend from the epidermis into the dermis and are found all over
the body, however they are particularly numerous in the palms of the
hands and the soles of the feet They regulate the body temperature by
allowing sweat to evaporate from the body.

There are two different types of sweat glands – apocrine and eccrine.
Eccrine glands are found all over the body surface and secrete in
response to heat. Apocrine glands are larger and deeper glands found in
the groin and underarm regions. These glands are under hormonal
control and therefore become active at puberty. The apocrine glands
produce sweat that decays to produce an unpleasant odour.

Hair Follicle
The hair follicle is an indentation of the epidermis with the walls of the
follicle being formed from a continuation of the cellular layer of the
skins surface.

• Inner Root Sheath – this layer is closest to the hair and has scale like cells that interlock with the cuticle to hold the hair firmly in place.
  The hair and the inner root sheath grow upwards, together. The inner root sheath is made up of three layers – cuticle of inner root sheath, Henley’s layer and Huxley’s layer.
• Outer Root Sheath – this is the follicle wall, it does not grow upwards but remains stationary in one place.
• Connective Tissue Sheath – this surrounds the rest of the follicle and the sebaceous gland. This is an extension of the papillary layer of the dermis and provides a sensory nerve and blood supply.

Blood Supply
Blood is supplied to the skin by small blood vessels known as blood
capillaries. Arterioles supply oxygenated blood that is rich in nutrients
and venules remove waste products and carbon dioxide. All parts of our
body require a blood supply as it provides the vital oxygen and nutrients
that tissues require in order to survive. In addition, the capillaries also
help to maintain the body temperature by dilating (widening) and
constricting (narrowing).

What is the dermal papilla and what is its function?
The dermal papilla is the blood supply for the hair and its follicle. It
provides food and oxygen, which are essential for the growth of the hair.
The dermal papilla is a separate organ that serves the follicle; it is not
part of the hair.

Arrector Pili Muscle
This muscle is attached to the hair follicle and it contracts when you are
cold or frightened causing the hair to stand up on end.
What is the function of the arrector pili muscle?
When the hairs stands on end they trap a layer of warm air around the
body to keep the body warm. When the muscle contracts it pulls on the
skin around the follicle opening, therefore producing goose pimples.

Nails
The nails are an extension of the epidermis and are therefore an
appendage of the skin. They are required to help with grasping and
protect the fingertips and toes.

Sebaceous Glands
These glands are found all over the body except for the palms of the
hands and the soles of the feet and produce the natural oil of the skin –
sebum. The gland is attached to the upper part of the follicle and its
duct enters directly into the hair follicle. The sebaceous glands become
more active at puberty due to the increased levels of androgens (male
hormone) being produced. Men generally secrete more sebum than
women, and you will usually note that the sebaceous glands become
less active as we get older.

What is the function of sebum?
Sebum is bactericidal and fungicidal and so prevents against infection,
it also provides protection and prevents the skin from drying out.

Nerves
Sensory nerve endings are found in the skin and detect changes in the
environment such as heat, cold, touch, pain and pressure. These send
messages to the central nervous system which will send messages back
via the motor nerves to stimulate a response.

There are different nerve endings that detect the different sensations:
Touch – meissners corpuscles
Pain – pain corpuscles
Pressure – pacinian corpuscles
Heat – ruffinis end corpuscles
Cold – krauses end bulb