Blood and Hemopoiesis
Overview of peripheral blood cell types (mature blood cells), blood smear.
is a specialized connective tissue composed of
suspended in intercellular ﬂ uid (or
). Blood cells include
red blood cells
white blood cells
are the most numerous. They are
biconcave disk–shaped cells without nuclei and are important in transportation of gases.
are very tiny cell fragments that have
no nuclei, cannot reproduce, and come from huge cells called
(Figs. 8-9B and 8-12). Platelets play an important role in
can be classi± ed as either
based on the absence or presence of speci± c granules in
their cytoplasm. Granulocytes are also called
because of the multiple lobes of their nuclei, but the term
is often used speci± cally for neutrophils. (1)
lack speci± c cytoplasmic granules but have the ability to divide.
fall into this category.
are the smallest cells in the leukocyte series. Each has a round nucleus and a
small amount of cytoplasm. They can be found outside of the blood stream in lymphoid organs and connective tissues. Lymphocytes
can be classi± ed as
. They are associated with immunological defense functions. B lym-
phocytes can further differentiate into
(see Figs. 4-2B and 4-3A,B).
are the largest cells in the leukocyte series.
They have large, elongated, and often kidney-shaped nuclei. They can differentiate into
contain speci± c granules in their cytoplasm, and their nuclei are segmented. They are
terminal cells without the capability to divide further. Granulocytes include
the most abundant leukocytes in circulating blood. Each cell has a multilobed nucleus and a pale pink cytoplasm that contains primary
and secondary (speci± c) granules. Neutrophils play an important role in defense against bacterial infection.
speci± c granules that stain red with eosin dye. They usually have a bilobed, or occasionally a trilobed, nucleus. Eosinophils function
in controlling allergic reactions and in combating parasitic infections.
are the rarest of the leukocytes (<1%). They contain
large, speci± c granules that are deep violet with a Wright stain. Each basophil has a nucleus with two to three lobes that are not com-
pletely separated. Basophils, along with mast cells, are instigators of allergic reactions (see the introduction to this chapter).