The Integumentary System 119
Common Disease, Disorder, or ConditionBurnsBurns are classified into three major categories: first-degree, second-degree, and third-
degree. First- and second-degree burns can also be categorized as partial-- thickness
burns. These burns do not completely destroy the stratum germinativum’s basal layer
and regeneration of the epidermis will occur from both within the burn area or from the
edges of the burn.^
First-degree burns involve just the epidermis (Figure 6-3A). They can be caused
by brief contact with very hot or very cold objects. They can also be caused by sun-
burn, being overexposed to the harmful rays of the sun. Sunscreen should always be
used to protect the skin from sunburn. Symptoms of first-degree burns are redness and
pain. There may also be slight swelling or edema. These burns can heal in about^
7 days with no scarring.^
Second-degree burns involve both the epidermis and the dermis (Figure 6-3B).
With minor dermal involvement, symptoms will include redness, pain, swelling, and
blisters. Healing can take up to 2 weeks with no scarring. If there is major dermal in-
volvement, the burn can take several months to heal and the wound might appear
white. Scar tissue may develop.^
In third-degree burns, also called full-thickness burns, the epidermis and the
dermis are completely destroyed (Figure 6-3C). Recovery can only occur from the edge
of the burn wound. Interestingly, third-degree burns are usually painless because the
sensory receptors in the skin have been destroyed. The pain usually comes from the
area around the third-degree burn where first- and second-degree burns surround the
area. Third-degree burns usually require skin grafts because they take a long time to
heal and will form disfiguring scar tissue. Skin grafts may prevent some of these
complications and speed healing. Skin grafts use the epidermis and part of the dermis
from another part of the body, usually the buttocks or thighs, and the graft is then placed
on the burn. Interstitial fluid from the burn helps heal the area.
very obvious as on the head, in the armpits, and around the
genitalia. The amount of hair a person develops is re-lated
to complex genetic factors.
Each individual hair is composed of three parts (Figure
6 - 4): the cuticle, the cortex, and the medulla. The
outermost portion is the cuticle, which consists of sev-eral
layers of overlapping scalelike cells. The cortex is the
principal portion of the hair. Its cells are elongated and
united to form flattened fibers. In people with dark hair,
these fibers contain pigment granules. The middle or
central part of the hair is called the medulla. It is com-
posed of cells with many sides. These cells frequently
contain air spaces. There are other parts to the anatomy of a
hair. The shaft is the visible portion of the hair. The root
is found in an epidermal tube called the hair follicle. The
follicle is made of an outer connective tissue sheath
and an inner epithelial membrane continuous with the
stratum germinativum.
Attached to the hair follicle is a bundle of smooth
muscle fibers that make up the arrector (ah-REK-tohr)
pili (PIH-lye) muscle. This muscle causes the goose flesh
appearance on our skin when we get scared or when we get
a chill. The muscle is involuntary and when it contracts it
pulls on the hair follicle, causing the hair to “stand on its
end.” We see the goose flesh appearance where hair is
scarce. When dogs or cats get angry, their hairs stand up on
the nape of their necks. This is all the result of contraction
of the arrector pili muscles.Hair Growth
Hair growth is similar to the growth of the epider-mis. Note
that the hair follicle is an involution of the