Figure 214

Sagittal section of the human testis, a. This schematic diagram shows a midsagittal section of the human testis. The genital duct system, which includes the tubuli recti, rete testis, efferent ducts, duct of the epididymis, and ductus deferens, is also shown. Note the thick connective tissue covering, the tunica albuginea, and the surrounding tunica vaginalis. (Modified from Dym M. In: Weiss L, ed. Cell and Tissue

Biology: A Textbook of Histology. 6th ed. Baltimore: Urban & Schwarzenberg, 1988.) b. Sagittal section of a H&E-stained section of the testis and the head and body of the epididymis. Again note the surrounding tunica albuginea and tunica vaginalis. Only a small portion of the rete testis is visible in this section. Its connection with the excurrent duct system is not evident in the plane of this section. x3.

ductus deferens efferent ductules body of epididymis mediastinum testis rete testis seminiferous tubule septum tunica albuginea tunica vaginalis

Each lobule consists of several highly convoluted seminiferous tubules

Each lobule of the testis consists of 1 to 4 seminiferous tubules in which sperm are produced and a connective tissue stroma in which Ley dig, or interstitial, cells are contained (Fig. 21.5). Each tubule within the lobule forms a loop and, because of its considerable length, is highly convoluted, actually folding on itself within the lobule. The ends of the loop are located near the mediastinum of the testis, where they assume a short straight course. This part of the seminiferous tubule is called the straight tubule (tubuli recti). It becomes continuous with the rete testis, an anastomosing channel system within the mediastinum.

The seminiferous tubules consist of a seminiferous epithelium surrounded by a tunica propria

Each seminiferous tubule is approximately 50 cm long (range, 30 to 80 cm) and 150 to 250 pan in diameter. The seminiferous epithelium is an unusual and complex stratified epithelium composed of two basic cell populations:

• Sertoli cells, also known as supporting, or sustentacu-lar, cells. These cells do not replicate after puberty. Sertoli cells are columnar cells with extensive apical and lateral processes that surround the adjacent spermatogenic cells and occupy the spaces between them. However, this elaborate configuration of the Sertoli cells cannot be seen distinctly in routine hematoxylin and eosin (H&E) preparations. Sertoli cells give structural organization to the tubules as they extend through the full thickness of the seminiferous epithelium.

• Spermatogenic cells, which regularly replicate and differentiate into mature sperm. These cells are derived from primordial germ cells originating in the yolk sac that colonize the gonadal ridges during early development of the testis. Spermatogenic cells are organized in poorly defined layers of progressive development between adjacent Sertoli cells (Fig. 21.6). The most imraa-

- tunica albugínea

- tunica albugínea

blood vessels septum

seminiferous tubules g?

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