Function of skin

1) Regulation of Body Temperature

In response to high environmental temperature or strenuous exercise, the
evaporation of sweat from the skin surface helps lower an elevated body
temperature to normal. In response to low environmental temperature,
production of sweat is decreased, which helps conserve heat. Changes in
the flow of blood to the skin also help regulate body temperature.

2) Protection

The skin covers the body and provides a physical barrier that protects
underlying tissues from shocks, physical abrasion, bacterial invasion,
dehydration, and ultraviolet (UV) radiation. Hair and nails also have
protective functions.

3) Sensation

The skin contains abundant nerve endings and receptors that detect
stimuli related to temperature, touch, pressure, and pain and relate the
information to the nervous system.

4) Excretion

Besides removing heat and some water from the body, sweat also is the
vehicle for excretion of a small amount of salts and several organic
compounds by integumentary glands.

5) Storage of Nutrients

Lipids are stored in adipocytes in the dermis and in adipose tissue in the
subcutaneous layer. These are made available to the body when there is
depletion which may be due to starvation.

6) Blood Reservoir

The dermis of the skin houses extensive networks of blood vessels that
carry 8 to 10% of the total blood flow in a resting adult. In moderate
exercise, skin blood flow may increase, which helps dissipate heat from
the body. During hard exercise, however, skin blood vessels constrict
(narrow) somewhat, and more blood is able to circulate to contracting

7) Synthesis of Vitamin D

Vitamin D is a group of closely related compounds. Synthesis of
vitamin D begins with activation of a precursor molecule in the skin by
ultraviolet (UV) rays in sunlight. Enzymes in the liver and kidneys then
modify the molecule, finally producing calcitriol; the most active form
of vitamin D. Calcitriol contributes to the homeostasis of body fluids by
aiding absorption of calcium in foods. According to the synthesis
sequence just described, vitamin D is a hormone, since it is produced in
one location in the body, transported by the blood, and then exerts its
effect in another location. In this respect, the skin may be considered an
endocrine organ.