Male Reproductive System
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. The Male Reproductive System >
The Male Reproductive System: Introduction
The male reproductive system is composed of the testes, genital ducts, accessory glands, and penis (Figure 21–1). The dual function of the testis is to produce spermatozoa and hormones. The genital ducts and accessory glands produce secretions that, aided by smooth muscle contractions, conduct spermatozoa toward the exterior. These secretions also provide nutrients for spermatozoa while they are confined to the male reproductive tract. Spermatozoa and the secretions of the genital ducts and accessory glands make up the semen (from Latin, meaning seed), which is introduced into the female reproductive tract through the penis. Although testosterone is the main hormone produced in the testes, both testosterone and one of its metabolites, dihydrotestosterone, are necessary for the physiology of men.
Figure 21–1.
The male genital system. The testis and the epididymis are shown in different scales than the other parts of the reproductive system. Note the communication between the testicular lobules.
Testes
Each testis is surrounded by a thick capsule of dense connective tissue, the tunica albuginea. The tunica albuginea is thickened on the posterior surface of the testis to form the mediastinum testis, from which fibrous septa penetrate the gland, dividing it into about 250 pyramidal compartments called the testicular lobules (Figure 21–2). These septa are incomplete, and there is frequent intercommunication between the lobules. Each lobule is occupied by one to four seminiferous tubules enmeshed in a web of loose connective tissue that is rich in blood and lymphatic vessels, nerves, and interstitial cells, also known as Leydig cells. Seminiferous tubules produce male reproductive cells, the spermatozoa, whereas interstitial cells secrete testicular androgens.
Figure 21–2.
Ducts of the testis and the ductus epididymis.
. The Male Reproductive System >
The Male Reproductive System: Introduction
The male reproductive system is composed of the testes, genital ducts, accessory glands, and penis (Figure 21–1). The dual function of the testis is to produce spermatozoa and hormones. The genital ducts and accessory glands produce secretions that, aided by smooth muscle contractions, conduct spermatozoa toward the exterior. These secretions also provide nutrients for spermatozoa while they are confined to the male reproductive tract. Spermatozoa and the secretions of the genital ducts and accessory glands make up the semen (from Latin, meaning seed), which is introduced into the female reproductive tract through the penis. Although testosterone is the main hormone produced in the testes, both testosterone and one of its metabolites, dihydrotestosterone, are necessary for the physiology of men.
Figure 21–1.
The male genital system. The testis and the epididymis are shown in different scales than the other parts of the reproductive system. Note the communication between the testicular lobules.
Testes
Each testis is surrounded by a thick capsule of dense connective tissue, the tunica albuginea. The tunica albuginea is thickened on the posterior surface of the testis to form the mediastinum testis, from which fibrous septa penetrate the gland, dividing it into about 250 pyramidal compartments called the testicular lobules (Figure 21–2). These septa are incomplete, and there is frequent intercommunication between the lobules. Each lobule is occupied by one to four seminiferous tubules enmeshed in a web of loose connective tissue that is rich in blood and lymphatic vessels, nerves, and interstitial cells, also known as Leydig cells. Seminiferous tubules produce male reproductive cells, the spermatozoa, whereas interstitial cells secrete testicular androgens.
Figure 21–2.
Ducts of the testis and the ductus epididymis.