Bauman Chapter 15 Answers to Critical Thinking Questions
p. 440
Some strains of Staphylococcus aureus produce exfoliative toxin, a chemical that
causes portions of the entire outer layer of the skin to be sloughed off in a disease called
scalded skin syndrome. Given that cells of the outer layers are going to fall off anyway,
why is this disease dangerous?
The outer layers of dead skin cells are tightly connected to each other and make a
formidable barrier against microbial invasion. Exfoliative toxin completely removes this
barrier, providing entry to a wide range of microbes.
p. 447
A medical laboratory technologist argues that granulocytes are a natural group, whereas
agranulocytes are an artificial grouping. Based on Figure 15.5, do you agree or disagree
with the lab tech? What evidence can you cite to justify your conclusion?
The technologists’ statement is a reasonable one. Granulocyte cells (neutrophils,
eosinophils and basophils) develop from a common progenitor (myeloid), whereas
agranulocytes (lymphocytes and monocytes) develop from different progenitors
(lymphoid and myeloid respectively).
p. 451
A patient has a genetic disorder that makes it impossible for her to synthesize
complement protein 8 (C8). Is her complement system nonfunctional? What major
effects of complement could still be produced?
Without C8 the complement system is unable to form Membrane Attack Complexes and
damage bacteria. The complement cascade will still produce factors C3a, C5b, which
attract phagocytes and enhance inflammation, and factor C3b that opsonizes pathogens,
making phagocytic attack easier.
p. 457
While using a microscope to examine a sample of pus from a pimple, Maria observed a
large number of macrophages. Is the pus from an early or a late stage of infection?
How do you know?
The pus is from a late stage of infection. Neutrophils arrive early in infection in large
numbers, and begin to die as they fight the infection. Monocytes arrive soon after, and
mature into macrophages, but do not die as the neutrophils do, thus many macrophages
and few neutrophils is an indication that the attack on the infection is winding down.
p. 458
How do drugs such as aspirin and ibuprofen act to reduce fever?
Aspirin and ibuprofen block the reactions that produce the molecules that “reset” the
body’s thermostat in the hypothalamus.
p. 461
1. Neighbor A received a chemical burn on his arm and was instructed by his physician
to take over-the-counter, anti-inflammatory medication for the painful, red, swollen
lesions. When Neighbor B suffered pain, redness, and swelling from an infected cut
on his foot, he decided to take the same anti-inflammatory drug because his
symptoms matched Neighbor A’s symptoms. How is Neighbor B’s inflammation like
that of Neighbor A? How is it different? Is it appropriate for B to medicate his cut
with the same medicine A used?
Neighbor A has inflammation that is a response to tissue damage caused by the burn.
Neighbor B is also experiencing inflammation in response to damage, but the damage
was done by invading microbes. B should not use the same medicine A used:
inflammation is an important process in fighting microbial invasion, and reducing
inflammation too much may allow the microbes to spread.
2.
What might happen to someone whose body did not produce C3? C5?
A body lacking C3 does not have a functional complement cascade: no factors that
enhance inflammation, attract phagocytes, opsonize antigens will be produced, and
MACs will not assemble.
The absence of C5 prevents the assembly of MACs, but the complement cascade
proceeds far enough to produce C3a and C3b which contribute to inflammation and are
chemotactic and opsonizing factors.
3.
Duncan, age 65, has had diabetes for 40 years, with resulting damage to the small
blood vessels in his feet and toes. His circulation is impaired. How might this
condition affect his vulnerability to infection?
Impaired circulation reduces the bodys’ ability to develop an inflammatory response and
to deliver the phagocytes and complement molecules needed to initiate the fight against
infection: Duncan is very vulnerable to infection.
4.
A patient’s chart shows that eosinophils make up 8% of his white blood cells. What
does this lead you to suspect? Would your suspicions change if you learned that
the patient had spent the previous 3 years as an anthropologist living among an
African tribe? What is the normal percentage of eosinophils?
In the United States, the primary reason for elevated eosinophils is allergies. However,
eosinophilia may also indicate infection by parasitic worms. The patient history verifies
the likelihood that the patient has an helminth infection. Normal eosinophil levels are 24%.
5.
There are two kinds of agranulocytes in the blood—monocytes and lymphocytes.
Janice notes that monocytes are phagocytic and that lymphocytes are not. She
wondered why two agranulocytes would be so different. What facts of
hematopoiesis can answer her question?
Monocytes develop from myeloid stem cells while lymphocytes develop from lymphoid
stem cells. “Agranulocyte” is a description of the appearance of the cytoplasm, not of
function or lineage.
6.
A patient has a genetic disorder that prevents him from synthesizing C8 and C9.
What effect would this have on his ability to resist blood-borne Gram-negative and
Gram-positive bacteria? What would happen if C3 and C5 fragments were also
inactivated?
The lack of C8 and C9 results in the inability to form membrane attack complexes
(MACs), which are particularly effective in damaging Gram-negative bacteria; therefore,
infections with Gram-negative bacteria may progress to dangerous levels. The
complement cascade can progess far enough in this patient to produce C3a, C3b, and
C5b, which contribute to inflammation and are chemotactic and opsonizing factors. As a
result, the inflammatory response to both Gram-positive and Gram-negative bacteria is
normal. If factors C3 and C5 were also missing, the complement factor contribution to
inflammation would be destroyed, reducing the vigor of the response to any invading
bacterium, Gram-positive or Gram-negative; the patient would be more susceptible to
dangerous bacterial infections.