Fundamentals of Anatomy and Physiology

308 Chapter 13

Red blood cells (erythrocytes) Platelets (thrombocytes)

White blood cells (leukocytes)

Granular

leukocytes

Basophil Neutrophil Eosinophil

Nongranular^
leukocytes

Lymphocyte Monocyte

Figure 13- 2 The classification of blood cells.

(^) ®
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Formation of Blood Cells:
Hematopoiesis
Blood cell formation is known as hematopoiesis (hem-
ah-toh-poy-EE-sis). Hematopoiesis occurs in red bone
marrow, which is also known as myeloid tissue. All
blood cells are produced by red bone marrow. However,
certain lymphatic tissue such as the spleen, tonsils, and
lymph nodes produce agranular leukocytes (lym-phocytes
and monocytes). They assist in the produc-tion of those
blood cells. All blood cells develop from undifferentiated
mesenchymal cells called stem cells or
hematocytoblasts- (hee-MAT-oh-SIGHT-oh-blastz)
(Figure 13-3).