Covering, Support, and Movement of the Body
degree, and third degree. Tird-degree burns are full-thickness
burns that require graFing for successful recovery.
Developmental Aspects of the Integumentary
Te epidermis develops from embryonic ectoderm; the dermis
(and hypodermis) develops from mesoderm.
Te fetus exhibits a downy lanugo coat. ±etal sebaceous glands
produce vernix caseosa, which helps protect the fetus’s skin from
its watery environment.
From Infancy to Adulthood
A newborn’s skin is thin. During childhood the skin
thickens and more subcutaneous fat is deposited. At puberty,
sebaceous glands are activated and terminal hairs appear in
In old age, the rate of epidermal cell replacement declines and
the skin and hair thin. Skin glands become less active. Loss
of collagen and elastic ﬁbers and subcutaneous fat leads to
wrinkling; delayed-action genes cause graying and balding.
Photodamage is a major cause of skin aging.
Metabolic functions. A vitamin D precursor is synthesized from
cholesterol by epidermal cells. Skin cells also play a role in some
Blood reservoir. Te extensive vascular supply of the dermis
allows the skin to act as a blood reservoir.
Excretion. Sweat contains small amounts of nitrogenous wastes
and plays a minor role in excretion.
Homeostatic Imbalances of Skin
Te most common skin disorders result from infections.
Te most common cause of skin cancer is exposure to ultraviolet
Basal cell carcinoma and squamous cell carcinoma are cured
if they are removed before metastasis. Melanoma, a cancer of
melanocytes, is less common but more dangerous.
In severe burns, the initial threat is loss of protein- and
electrolyte-rich body ﬂuids, which may lead to circulatory
collapse. Te second threat is overwhelming bacterial infection.
Te extent of a burn may be evaluated by using the rule of nines.
Te severity of burns is indicated by the terms ﬁrst degree, second
(Some questions have more than one correct answer. Select the best
answer or answers from the choices given.)
Which epidermal cell type is most numerous?
Which cell functions as part of the immune system?
Te epidermis provides a physical barrier due largely to the
Skin color is determined by
the amount of blood,
oxygenation level of the blood,
all of these.
Te sensations of touch and pressure are picked up by receptors
the stratum spinosum,
the stratum corneum.
Which is not a true statement about the papillary layer of the
it is largely areolar connective tissue,
it is most
responsible for the toughness of the skin,
it contains nerve
endings that respond to stimuli,
it is highly vascular.
Skin surface markings that reﬂect points of tight dermal
attachment to underlying tissues are called
Which of the following is not an epidermal derivative?
An arrector pili muscle
is associated with each sweat gland,
can cause a hair to stand up straight,
enables each hair
to be stretched when wet,
provides new cells for continued
growth of its associated hair.
Te product of this type of sweat gland includes protein and lipid
substances that become odoriferous as a result of bacterial action:
lubricates the surface of the skin and hair,
of cell fragments and fatty substances,
in excess may cause
all of these.
Te rule of nines is helpful clinically in
estimating the extent of a burn,
serious a cancer is,
Short Answer Essay Questions
Which epidermal cells are also called prickle cells? Which contain
keratohyaline and lamellar granules?
Is a bald man really hairless? Explain.
You go to the beach to swim on an extremely hot, sunny summer
aFernoon. Describe two ways in which your integumentary
system acts to preserve homeostasis during your outing.
Distinguish clearly between ﬁrst-, second-, and third-degree
Describe the process of hair formation, and list several factors
that may inﬂuence (a) growth cycles and (b) hair texture.
What color does carotene impart to the skin?
Why does skin wrinkle and what factors accelerate the wrinkling
Explain each of these familiar phenomena in terms of what you
learned in this chapter: (a) pimples, (b) dandruﬀ, (c) greasy hair
and “shiny nose,” (d) stretch marks from gaining weight,
Count Dracula, the most famous vampire, rumored to have killed
at least 200,000 people, was based on a real person who lived in
eastern Europe about 600 years ago. He was indeed a “monster,”
although he was not a real vampire. Te historical Count Dracula
may have suﬀered from which of the following? (Hint: See
Related Clinical ²erms.) (a) porphyria, (b) EB, (c) halitosis,
(d) vitiligo. Explain your answer.