Concepts of Human Anatomy & Physiology   5/e   Van De Graaff/Fox
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I. Introduction to the Reproductive System

Concept: A gene on the Y chromosome causes the embryonic gonads to differentiate into testes. Females lack a Y chromosome, and the absence of this gene results in the development of ovaries. The embryonic testes secrete testosterone, which triggers the development of male accessory sex organs and external genitalia. The absence of testes (rather than the presence of ovaries) in a female embryo causes the development of the female accessory sex organs.

II. Endocrine Regulation of Reproduction

Concept: The functions of the testes and ovaries are regulated by gonadotropic hormones secreted by the anterior pituitary. The gonadotropic hormones stimulate the gonads to secrete their sex steroid hormones, and these steroid hormones, in turn, have an inhibitory effect on the secretion of the gonadotropic hormones. This interaction between the anterior pituitary and the gonads forms a negative feedback loop.

III. Male Reproductive System

Concept: The interstitial (Leydig) cells of the testes are stimulated by LH to secrete testosterone-a potent androgen that acts to maintain the structure and function of the male accessory sex organs and to promote the development of male secondary sex characteristics. The sustentacular (Sertoli) cells in the seminiferous tubules of the testes are stimulated by FSH. The cooperative actions of FSH and testosterone are required to initiate spermatogenesis.

IV. Spermatic Ducts, Accessory Reproductive Glands, and the Penis

Concept: The spermatic ducts store spermatozoa and transport them from the testes to the urethra. The accessory reproductive glands add secretions to the spermatozoa in the formation of semen. Semen is discharged from the erect penis during ejaculation.

V. Development of the Reproductive System

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