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short-lived

(bilobed). Eosinophils moderate allergic reactions and defend against parasitic worm infestation. These cells make up 1% to 3% of the total number of circulating leukocytes (fig. 14.10).

Basophils (ba'so-filz) are similar to eosinophils in size and in the shape of their nuclei. However, they have

Shier-Butler-Lewis: Human Anatomy and Physiology, Ninth Edition

IV. Transport

14. Blood

© The McGraw-Hill Companies, 2001

Figure 14.9

A neutrophil has a lobed nucleus with two to five components (400x micrograph enlarged to 1050x).

Figure 14.9

A neutrophil has a lobed nucleus with two to five components (400x micrograph enlarged to 1050x).

Eosinophil Cell

Figure 14.11

A basophil has cytoplasmic granules that stain deep blue (400x micrograph enlarged to 1050x).

Figure 14.11

A basophil has cytoplasmic granules that stain deep blue (400x micrograph enlarged to 1050x).

Monocytes And Blood Vessel Cartoon

An eosinophil has red-staining cytoplasmic granules (400x micrograph enlarged to 1050x).

Figure 14.12

A monocyte may leave the bloodstream and become a macrophage (400x micrograph enlarged to 1050x).

An eosinophil has red-staining cytoplasmic granules (400x micrograph enlarged to 1050x).

Figure 14.12

A monocyte may leave the bloodstream and become a macrophage (400x micrograph enlarged to 1050x).

fewer, more irregularly shaped cytoplasmic granules than eosinophils, and these granules appear deep blue in basic stain. A basophil's granules can obscure a view of the nucleus. Basophils migrate to damaged tissues where they release histamine, which promotes inflammation, and heparin, which inhibits blood clotting, thus increasing blood flow to injured tissues. This type of leukocyte usually accounts for less than 1% of the leukocytes (fig. 14.11).

The leukocytes of the agranulocyte group include monocytes and lymphocytes. Monocytes generally arise from red bone marrow. Lymphocytes are formed in the organs of the lymphatic system as well as in the red bone marrow.

Monocytes (mon'o-sitz) are the largest blood cells, two to three times greater in diameter than red blood cells. Their nuclei are spherical, kidney-shaped, oval, or lobed. Monocytes leave the bloodstream and become macrophages that phagocytize bacteria, dead cells, and other debris in the tissues. They usually make up 3% to

9% of the leukocytes in a blood sample and live for several weeks or even months (fig. 14.12).

Lymphocytes (lim'fo-sltz) are usually only slightly larger than erythrocytes. A typical lymphocyte contains a large, spherical nucleus surrounded by a thin rim of cytoplasm. The major types of lymphocytes are T cells and B cells, both important in immunity. T cells directly attack microorganisms, tumor cells, and transplanted cells. B cells produce antibodies (an'ti-bod"ez) (see chapter 16, p. 665) which are proteins that attack foreign cells or proteins. Lymphocytes account for 25% to 33% of the circulating leukocytes. They may live for years (fig. 14.13).

99 Distinguish between granulocytes and agranulocytes.

^9 List five types of white blood cells, and explain how they differ from one another.

^9 Describe the function of each type of white blood cell.

Figure ure 14.13

Figure

The lymphocyte contains a large, spherical nucleus (400x micrograph enlarged to 1050x).

The lymphocyte contains a large, spherical nucleus (400x micrograph enlarged to 1050x).

Diapedesis Cell

Figure 14.14

Leukocytes can squeeze between the cells of a capillary wall and enter the tissue space outside the bloodstream.

Figure 14.14

Leukocytes can squeeze between the cells of a capillary wall and enter the tissue space outside the bloodstream.

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