Blood Plasma

Plasma is the clear, straw-colored, liquid portion of the blood in which the cells and platelets are suspended. It is approximately 92% water and contains a complex

Leukemia

The young woman had noticed symptoms for several months before she finally went to the doctor. At first it was just fatigue and headaches, which she attributed to studying for final exams. She had frequent colds and bouts of fever, chills, and sweats that she thought were just minor infections. When she developed several bruises and bone pain and noticed that her blood did not clot very quickly after cuts and scrapes, she consulted her physician, who examined her and took a blood sample. One glance at a blood smear under a microscope alarmed the doctor—there were far too few red blood cells and platelets and too many white blood cells. She sent the sample to a laboratory to diagnose the type of leukemia, or cancer of the white blood cells, that was causing her patient's symptoms.

The young woman had myeloid leukemia. Her red bone marrow was producing too many granulocytes, but they were immature cells, unable to fight infection (fig. 14A). This explained the frequent illnesses. The leukemic cells were crowding out red blood cells and their precursors in the red marrow, causing her anemia and resulting fatigue. Platelet deficiency (thrombocytopenia) led to increased tendency to bleed. Finally, spread of the cancer cells outside the marrow painfully weakened the surrounding bone. Eventually, if she wasn't treated, the cancer cells would spread outside the circulatory system, causing other tissues that would normally not produce white blood cells to do so.

A second type of leukemia, distinguished by the source of the cancer cells, is lymphoid leukemia. These cancer cells are lymphocytes, produced in lymph nodes. Many of the symptoms are similar to those of myeloid leukemia. Sometimes a person has no leukemia symptoms at all, and a routine blood test detects the condition.

Leukemia is also classified as acute or chronic. An acute condition appears suddenly, symptoms progress rapidly, and death occurs in a few months without treatment. Chronic forms begin more slowly and may remain undetected for months or even years or, in rare cases, decades. Without treatment, life expectancy after symptoms develop is about three years. With treatment, 50% to 80% of patients enter remission, a period of stability that may become a cure. Chemotherapy may be necessary for a year or two to increase the chances of long remission.

Leukemia treatment includes correcting symptoms by giving blood transfusions, treating infections, and using drugs that kill cancer cells. Several drugs in use for many years have led to spectacular increases in cure rates, particularly for acute lymphoid leukemia in children. Some newer treatments offer hope for other types of leukemia, too. For example, alpha interferon treats a chronic form called hairy cell leukemia that mostly affects adult males, and a type of retinoic acid treats acute promyelo-cytic leukemia. A bone marrow transplant can cure leukemia, but it is a very risky procedure. ■

Figure 14A

Figure 14A

(a) Normal blood cells (400x micrograph enlarged to 800x). (b) Blood cells from a person with granulocytic leukemia (400x micrograph enlarged to 800x). Note the increased number of leukocytes.

Shier-Butler-Lewis: I IV. Transport I 14. Blood I I © The McGraw-Hill

Human Anatomy and Companies, 2001

Physiology, Ninth Edition

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