The male reproductive system consists of a series of organs, tubules, and accessory glands that function in the production, nourishment, temporary storage, and intermittent discharge of spermatozoa (sperm), the male germ cells. The organs and structures that comprise the male reproductive system include the following:
Testes. Contain the seminiferous tubules, which produce the spermatozoa, and Leydig cells, which secrete the male sex hormone testosterone.
Intratesticular and extratesticular genital ducts. Carry spermatozoa through the male reproductive system.
Accessory glands. Produce secretions, which nourish spermatozoa and comprise the major portion of semen.
Penis. Delivers semen to the female genital tract during intercourse; also conducts urine from the urinary bladder to outside the body.
Spermatozoa are produced in males continuously from adolescence throughout life through a complex process termed spermatogenesis, which involves a stereotypical pattern of mitotic and meiotic divisions of spermatogenic cells in the seminiferous epithelium of the testes.
Testosterone is the most important circulating androgen and is required for the development, maturation, and proper function of the male reproductive organs and for various secondary sex characteristics. The production of testosterone is under complex hormonal control involving the testes, pituitary gland, and hypothalamus.
ORGANIZATION OF THE TESTIS
The primary male sex organ is the testis, which functions as both an exocrine gland, with spermatozoa as the secretory product, and as an endocrine gland, which produces the male sex hormone testosterone. The paired testes, along with the epididymis and the initial portion of the ductus (vas) deferens, are located outside the body in the scrotum (Figure 16-1A). The overall organization of the testis is as follows:
Each testis is surrounded by a dense, fibrous connective tissue capsule covered with mesothelium, called the tunica albuginea. The tunica albuginea thickens posteriorly to form the mediastinum testis, which bulges into the interior of the testis. Sperm ductules, blood and lymphatic vessels, and nerves enter and exit the testis through the mediastinum testis.
The testis consists of numerous seminiferous tubules (the site of sperm production) supported by interstitial tissue containing Leydig cells, which produce testosterone.
Connective tissue septa radiate from the mediastinum testis to divide the testis into approximately 250 lobules, each containing anywhere from one to four seminiferous tubules.
A series of genital ducts within the testis (the tubuli recti, rete testis, and ductuli efferentes) convey sperm from the seminiferous tubules to the epididymis.
Overview of the male reproductive system and the testis. A. Male reproductive organs. B. Cross section through the testis. Only a small region of seminiferous tubules and the thick connective tissue capsule, called the tunica albuginea, are shown here. C. Cross section of seminiferous tubules in the testis shown at higher magnification than in part B. ...
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