HUMAN BIOLOGY

152 Chapter 8

blood disorders

Epstein-Barr virus. The infection triggers the overproduc-

tion of lymphocytes. The patient feels achy and tired and

runs a low-grade fever for several weeks as the highly

contagious disease runs its course.

The most notorious virus that attacks white blood cells

is HIV, the human immunodeficiency virus, which causes

AIDS. Its ability to kill lymphocytes of the immune system

is a major topic in Chapter 9.

Leukemias are often called “blood cancers,” but in fact

they are the result of cancer in bone marrow. The word

“leukemia” means white blood, and the hallmark of leuke-

mias (like other cancers) is runaway multiplication of the

abnormal cells. This unchecked growth of white blood cells

destroys healthy bone marrow.

In the most serious forms of leukemia, which tend

to strike children, the marrow cavities in bones become

choked with cancerous white blood cells. As other types

of blood cells (and stem cells) are excluded, typical symp-

toms of leukemia develop—fever, weight loss, anemia,

internal bleeding, pain, and susceptibility to infections.

Modern treatments now save thousands of lives, and

there is hope that experimental gene therapies may pro-

vide more help. Figure 8.11 shows cells of one type of

leukemia, called chronic myelogenous leukemia.

Carbon monoxide poisoning prevents

hemoglobin from binding oxygen

Carbon monoxide, or CO, is a colorless, odorless gas.

It is present in auto exhaust fumes and in smoke from

burning wood, coal, charcoal, and

tobacco. It binds to hemoglobin at

least 200 times more tightly than

oxygen does. As a result, breath-

ing even tiny amounts of it can tie

up half of the body’s hemoglobin

and prevent tissues from receiving

the oxygen they need. CO poison-

ing is especially dangerous because

an affected person may not realize

that the symptoms—headache and

feeling “woozy”—are signs of life-

threatening distress.

anemias are red blood cell disorders

At least half a dozen anemias (meaning “no blood”) are

signs that red blood cells are not delivering enough oxygen

to meet body needs. All anemias result from other underly-

ing problems. To varying degrees they make a person feel

tired and listless, among other symptoms.

Two common types of anemia result from nutrient defi-

ciencies. For example, iron-deficiency anemia develops when

the body’s iron supply is too low to form enough hemoglobin

(with its iron-containing heme groups) (Figure 8.10). Folic

acid and vitamin B 12 both are needed for the production of

red blood cells in bone marrow. A deficiency of either one can

lead to pernicious anemia. A balanced diet usually provides

both nutrients, but other conditions can prevent them from

being absorbed.

The rare malady aplastic anemia arises when red bone

marrow, including the stem cells that give rise to red and

white blood cells and platelets, has been destroyed by

radiation, drugs, or toxins.

“Hemolytic” means blood breaking, and hemolytic anemias

develop when red blood cells die or are destroyed before

the end of their normal useful life. The root cause may be

an inherited defect, as in sickle-cell anemia, in which red

blood cells take a sickle shape and can burst. Chapter 19

looks more fully at the bodywide effects of these changes.

Worldwide, malaria is a major cause of hemolytic

anemia. It is caused by a protozoan that is transmitted

by mosquitoes. One life stage of this pathogen multiplies

inside red blood cells, leading to disease symptoms such

as fever, chills, and trembling. Eventually the red blood

cells burst. In 2012, malaria caused nearly 1 million deaths,

mostly among African children.

Like those with sickle-cell anemia, those with the inher-

ited disease thalassemia also produce abnormal hemoglo-

bin. Too few healthy red blood cells form, and those that do

form are thin and extremely fragile.

Viruses and leukemias affect white blood cells

Our white blood cells also can be affected by disease. For

example, infectious mononucleosis is caused by the

8.9

Figure 8.10 In anemias red blood cells can’t deliver sufficient oxygen to tissues. Here

you are looking at scanning electron micrographs of A normal RBCs and B RBCs deprived

of iron. They are pale because they lack the normal amount of hemoglobin. (A–B: Science Source)

A Normal red blood cells B Iron-deficient red blood cells

Figure 8.11 This image shows blood from a person with

chronic myelogenous leukemia. Abnormal white blood cells

(purple) are starting to crowd out normal cells.

Michael J. Klein, M.D./Cultura Creative/Alamy

Copyright 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).