Page 807 - Atlas of Histology with Functional Correlations

FIGURE 20.10 ■ Seminiferous tubules, straight tubules, rete testis, and efferent

ductules (ductuli efferentes). Stain: hematoxylin and eosin. Low magnification
(inset: high magnification).

FUNCTIONAL CORRELATIONS 20.2 ■

Hormones of Male Reproductive Organs

Normal maintenance of spermatogenesis in adult testes depends on two

hormones: follicle-stimulating hormone (FSH) and luteinizing hormone
(LH), also called interstitial cell–stimulating hormone (ICSH). The
neurons in the hypothalamus secrete gonadotropin-releasing hormone
(GnRH) that stimulates the gonadotrophs in the adenohypophysis of the

pituitary gland to synthesize and release LH. Normal spermatogenesis
depends on LH, which binds to LH receptors on interstitial cells (of Leydig)
and stimulates the synthesis of testosterone. FSH is also produced by
gonadotrophs in the pituitary gland. FSH stimulates Sertoli cells to

synthesize and release androgen-binding protein (ABP) into the
seminiferous tubules, where it combines with and increases testosterone
concentration in the vicinity of the developing spermatogenic cells, which
then stimulates normal spermatogenesis. An increased concentration of

testosterone in the seminiferous tubules is essential for spermatogenesis. In
addition, the structure and function of the accessory reproductive glands, as
well as the development and maintenance of male secondary sexual
characteristics, are dependent on proper testosterone levels.

An excessive level of testosterone produces an inhibitory effect on the
hypothalamic neurons and the hypophyseal cell release of additional FSH by
the hormone inhibin that is also secreted by the Sertoli cells. Sertoli cells
also produce activin that exerts an opposite and positive effect on FSH
release.

FIGURE 20.11 | Ductuli Efferentes and Tubules of

Ductus Epididymis

The ductuli efferentes (1), or efferent ductules, emerge from the mediastinum
on the posterosuperior surface of the testis and connect the rete testis with the
ductus epididymis. The ductuli efferentes are located in the connective tissue (2,

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