86 Chapter 4
Despite being controversial,
embryonic stem cells have a
key advantage over adult ones.
The adult stem cells can give
rise to a few types of tissues—
such as cartilage—but embryonic
stem cells can, in theory, give
rise to all the different types of
body tissues. Recently, however, research teams in Japan and
the United States succeeded in chemically coaxing adult stem
cells from mice to behave much more like embryonic ones.
The process—briefly “shocking” the adult cells with an acidic
bath—is relatively simple. If it can work with adult stem cells
from humans, it may be the basis for therapies that use adult
stem cells to regenerate cells a damaged tissue needs to heal
from injury or disease.your Future
- After you eat too many carbohydrates and proteins, your
body converts the excess to storage fats, which accumulate
in.
a. loose connective tissue c. adipose tissue
b. dense connective tissue d. both b and c - The body’s internal environment consists of.
a. blood plasma c. the five body cavities
b. interstitial fluid d. both a and b - In , physical and chemical aspects of the body
are being kept within tolerable ranges by controlling
mechanisms.
a. positive feedback c. homeostasis
b. negative feedback d. metastasis - detect specific environ mental changes, an
pulls different bits of information together in the selection
of a response, and carry out the response. - Match the concepts:
muscles and glands a. integrating center
positive feedback b. reverses an altered
sites of body receptors condition
negative feedback c. eyes and ears
brain d. effectors
e. intensifies the original
condition
CritiCaL thinKing
- In people who have the genetic disorder anhidrotic
ectodermal dysplasia, patches of tissue have no sweat
glands. What kind of tissue does this disorder affect? - The disease called scurvy results from a deficiency of
vitamin C, which the body uses to synthesize collagen.
Explain why scurvy sufferers tend to lose teeth, and why
any wounds heal much more slowly than normal, if
at all. - The man pictured in
Figure 4.17 wears skin
ornaments applied by
piercing. Among other
functions, the skin is a
barrier to potentially
dangerous bacteria, and
some people object to
extensive body piercing
on the grounds that
it opens the door to
infections. Explain why
you do or don’t agree
with this objection. - Porphyria is a genetic
disorder. In one form,
affected people lack
enzymes of a metabolic
pathway that forms heme,
the iron-containing group
in hemoglobin. Chemicals called porphyrins accumulate and
cause terrible symptoms, especially if the person is exposed
SPL/Science Sourceto sunlight. Sores and
scars form on the skin
(Figure 4.18). The gums
shrink away from the
teeth and the canine teeth
may begin to look like
fangs. Drinking alcohol
or eating garlic makes
symptoms worse. People
with porphyria can avoid
sunlight and aggravating
substances. They also can
get injections of heme
from normal red blood
cells. If you are familiar
with vampire stories,
which date from centuries
ago, can you think of a
reason why they may
have arisen among people
who knew nothing about
the cause of porphyria?- Your housemate comes down with the latest stomach
flu virus and develops frequent, watery diarrhea that
alternates with vomiting episodes. After a day of misery,
she is so listless that you insist on taking her to the
emergency room. A nurse hooks her up to an IV drip
of saline solution (slightly salty water) and insists that
she stay in ER until the full amount has entered her
bloodstream. Why was this the appropriate emergency
treatment for your housemate?
F i g u r e 4.18 Sun exposure
causes ulcers and blisters to
form on the skin of a person
affected by porphyria.F i g u r e 4.17 This young man
has chosen to undergo
multiple body piercings.Jason Todd/Photonica/Getty ImagesDR Zara/AGE FotostockCopyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).