p r o c e ss
d iag ram
The Skin Plays a Number of Roles in the Body
how the skin contributes to body tem-
perature regulation.
the processes of epidermal and deep
wound healing.
the role of the skin in cutaneous
types of burns and their consequences.
ou may not think much about what the skin
does, but it performs essential functions for
your health and well being. Let’s look at these
functions. Your skin helps regulate your body
temperature in many ways:
Because the skin’s surface area is so large (2 m2, or
22 ft2), your body is able to radiate to the outside air
vast amounts of heat that your body has produced.
The eccrine glands produce sweat to help eliminate
heat via evaporation.
The skin acts as a large reservoir of blood (8%—10%
total blood flow). When you are hot, increased blood
flow to the skin delivers more heat to be radiated away
and contributes to higher sweat production. When you
are cold, reduced blood flow to the skin conserves body
heat and reduces sweat production.
When you are cold, arrector pili contract to raise the
angle of body hairs and cause goose bumps. The raised
body hair reduces air microcirculation immediately
above the skin’s surface. The reduced air circulation
helps impede the loss of body heat via the skin.
The skin forms a protective barrier for the internal organs.
Keratin protects the body from heat, abrasion, chemicals,
and microbes. Keratinocytes resist invasion by microbes,
and the Langerhans cells alert the immune system to the
invaders. Furthermore, the skin can usually repair itself
following minor injuries, such as cuts and tears. See Fig-
ures 4.6 and 4.7 for descriptions of how the epidermis
and dermis self-repair—processes called
epidermal wound
deep wound healing,
E piderm al w o u n d healing • Figure 4.6
An injury such as an abrasion removes the
outer layers of the epidermis, possibly down
to the dermis. The stratum basale cells repair
the wound by moving over, filling the void,
and making new epidermal layers.
Basal epithelial cells on
the edge detach from
basement membrane,
migrate into wound,
and enlarge.
Initial injury
Stratum basale
(basal epithelial
— Epidermis
— Basement membrane
Adjacent basal cells
slide along into the
wound as a sheet.
Epidermal growth factor
stimulates stem cells to
divide and replace the
migrating cells.
When migrating cells meet, they stop moving
(contact inhibition), grow, and build new
strata, thereby completing the wound repair.
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