HUMAN BIOLOGY

154 Chapter 8

Dangerous blood clots are more common

in people who have cancer or blood

poisoning (septicemia). Although the

reason wasn’t clear, medical researchers

once suspected it might have something

to do with inflammation, which is part

of the body’s response to infection or

the onset of cancer. Now scientists

in Germany have identified genetic changes triggered by

inflammation that block feedback mechanisms which normally

shut down the activity of thrombin. As described in Section 8.7,

this enzyme promotes the formation of a clot’s fibrin net. When

normal controls on thrombin go awry, blood clots are much more

likely to form. Thrombin also promotes the formation of new

blood vessels that cancerous tumors need to grow. In the not-

too-distant future, drugs and other therapies that slow “runaway”

thrombin production may be powerful new tools in treating

clotting associated with cancer and other diseases as well.

Eye of Science/Science Source

3. Add the missing labels to this diagram of hemoglobin.
   Then, on a separate sheet of paper, list the factors that
   affect the tendency of hemoglobin to bind with oxygen.
   6. Blood typing determines the particular on a
   person’s.
   a. antibodies; white blood cells
   b. self markers; red blood cells
   c. antibodies; red blood cells
   d. self markers; white blood cells
   7. The formation of a blood clot.
   a. is an alternative to hemostasis
   b. can occur only through an intrinsic mechanism that
   involves substances in the blood itself
   c. is just one of several mechanisms of hemostasis
   d. relies on the action of a single clotting factor
   8. Match the blood terms with the best description.
   red blood cell a. plug leaks
   platelets b. blood markers
   stem cell c. blood cell source
   plasma d. erythrocyte
   A, B, O e. more than half of
   whole blood

CritiCaL tHinKing

1. Thrombocytopenia (throm-bo-sye-tow-pee-ne-ah)
   is a disorder that develops when certain drugs,
   bone marrow cancer, or radiation destroys red bone
   marrow, including stem cells that give rise to platelets.
   Predict a likely symptom of this disorder.


2. As the text described, when a person’s red blood cell count
   drops, the kidneys receive less oxygen. In response they
   release erythropoietin, which prompts the bone marrow
   to make more red blood cells. As the rising number of red
   blood cells carry more oxygen to the kidneys, they stop
   releasing the hormone. What type of homeostatic control
   mechanism are we talking about here?


3. Blood-feeding insects such as mosquitoes inject an
   anticoagulant into the victim’s bloodstream. How does
   this benefit the insect?


4. What is an agglutination response? How can it be avoided
   when blood is transfused?


5. What is the function of hemostasis? What are the two ways
   a blood clot can form?

seLF-Quiz Answers in Appendix VI

1. Which of the following statements about blood plasma
   is/are accurate?
   a. Blood plasma is mostly water.
   b. Blood plasma transports only a few substances,
   including blood cells, several proteins, and some
   hormones.
   c. Blood plasma transports blood cells, as well as proteins
   and many other substances.
   d. Molecules of albumin make up the majority of blood
   plasma proteins.


2. The produces red blood cells, which transport
   and some.
   a. liver; oxygen; mineral ions
   b. liver; oxygen; carbon dioxide
   c. bone marrow; oxygen; hormones
   d. bone marrow; oxygen; carbon dioxide


3. The produces white blood cells, which function in
   and.
   a. liver; oxygen transport; defense
   b. lymph glands; oxygen transport; stabilizing pH
   c. bone marrow; day-to-day housekeeping; defense
   d. bone marrow; stabilizing pH; defense


4. In the lungs, the main factor in boosting the tendency of
   hemoglobin to bind with and hold oxygen is.
   a. temperature c. acidity (pH)
   b. the amount of O 2 relative to d. all are equally
   the amount of CO 2 in plasma important


5. Which of the following statements about red blood cells
   is false?
   a. They live about 120 days before being replaced.
   b. They lack a nucleus and other organelles when they
   are mature.
   c. They are replaced when the hormone EPO stimulates
   stem cells in bone marrow.
   d. They are replaced as part of a negative feedback loop in
   which kidney cells monitor blood oxygen levels.
   e. All the above statements are true except b, because all
   cells require a nucleus in order to function properly.

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