Transcript 4The Function of Skin

The Function of Skin
The skin has four basic
functions
I. Protection
A. Physical barrier to disease, dirt, and
dehydration
1. Bacteria and other invaders are
prevented entry by the top dead layer
of skin and the acidic, oily secretion
from sebaceous glands (sebum).
2. Keratinization of the dead skin
outer layer also prevents water from
entering or leaving the skin.
The progressive maturation of a
keratinocyte is characterized
by the accumulation of
keratin, called keratinization.
The cells of the stratum
granulosum (SGR)
accumulate dense basophilic
keratohyalin granules (seen
on the close-up view).
These granules contain lipids,
which along with the
desmosomal connections,
help to form a waterproof
barrier that functions to
prevent fluid loss from the
body.
B. The skin also protects the rest of your
body from harmful ultraviolet radiation
through the production of melanin in the
melanocytes. Melanin absorbs the sun’s
rays.
MELANOCYTES
II. Vitamin D Synthesis
A.The skin produces a precursor to
Vitamin D. The sun’s rays convert this
into Vitamin D.
B.Vitamin D is converted in the liver
and kidneys into the hormone calcitriol,
which regulates bone growth.
III. Touch and Talk
A. Special nerve
receptors control
pressure, pain, and
temperature
sensing.
B. A great many of these receptors
occur in the hands.
IV. Regulation of Body Temperature
A. Only 40% of the energy from ATP is
used. The rest is given off as heat from
the muscles.
B. The skin keeps the amount needed
and releases the rest through sweat
C. Blood vessels control the temperature
regulation by dilating or constricting.
D. Bad things happen when a constant
temp. is not kept
1. Hyperthermia—Higher body temp.
than normal results in dehydration
(from excess sweating) and heat
stroke.
2. Hypothermia—Lower body temp.
than normal interferes with the
body’s normal functions and
eventually ends in death.