Page 801 - Atlas of Histology with Functional Correlations

and give rise to type A and type B spermatogonia. The final mitotic division of

type B spermatogonia produces primary spermatocytes (2, 9).

The primary spermatocytes (2, 9) are the largest germ cells in the
seminiferous tubules (8) and occupy the middle region of the germinal
epithelium. Their cytoplasm contains large nuclei with coarse clumps or thin
threads of chromatin. The first meiotic division of the primary spermatocytes

(Fig. 20.8, I, 5) produces smaller secondary spermatocytes with less-dense
nuclear chromatin (Fig. 20.8, I, 3). Because the secondary spermatocytes
undergo a second meiotic division shortly after their formation, they are
infrequently seen in the seminiferous tubules (8).

The second meiotic division produces smaller spermatids (4) (Fig. 20.8, I,
2) that are grouped in the adluminal compartment of the seminiferous tubule (8)
and closely associated with supportive Sertoli cells (6, 10). The more mature
spermatids (4, upper leader) are located in the periphery of the germinal
epithelium with their nuclei condensed and elongated and their tails extending

into the lumen of the seminiferous tubule (8). The more immature spermatids (4,
lower leader) are round cells with dense-staining round nuclei that are located
deeper in the germinal epithelium. All developing spermatids (4) are embedded

in the Sertoli cell (6, 10) cytoplasm and are grouped in the adluminal
compartment of the seminiferous tubule (8). Here, the spermatids (4)
differentiate through spermiogenesis and are released into seminiferous tubules
(8) as sperm.

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