Figure 2113

Schematic drawing of the stages of the human seminiferous epithelium. This diagram shows each of the six recognizable cell associations that occur in the cycle of the human seminiferous epithelium.

type A pale spermatogonium type A dark spermatogonium primary spermatocytes in division secondary spermatocytes diplotene spermatocyte oping sperm that attach to their surface after meiosis. Sertoli cells contain an extensive sER, a well-developed rER, and stacks of annulate lamellae. They have numerous spherical and elongated mitochondria; a well-developed Golgi apparatus; and varying numbers of microtubules, lysosomes, lipid droplets, vesicles, glycogen granules, and filaments. A sheath of 7- to 9-nm filaments surrounds the nucleus and separates it from other cytoplasmic organelles.

The euchromatic Sertoli cell nucleus, a reflection of this very active cell, is generally ovoid or triangular and may have one or more deep infoldings. Its shape and location vary. It may be flattened, lying in the basal portion of the cell near and parallel to the base of the cell, or it may be triangular or ovoid, lying near or some distance from the base of the cell. In some species, the Sertoli cell nucleus contains a unique tripartite structure that consists of a RNA-containing nucleolus flanked by a pair of DNA-containing bodies called kaiyosomes (Fig. 21.16).

In man, characteristic inclusion bodies (of Charcot-Bottcher) are found in the basal cytoplasm. These slender fusiform crystalloids measure 10 to 25 fxm long by 1 (mm wide and are visible in routine histologic preparations. With transmission electron microscopy, they are resolved as bundles of poorly ordered, parallel or converging, straight, dense 15-nm-diameter filaments (see Fig. 21.15). Their chemical composition and function are unknown

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