LEARNING OBJECTIVE: Recall the parts of the male reproductive system and their function(s).

The organs of the male and female reproductive systems are concerned with the process of reproducing offspring, and each organ is adapted to perform specialized tasks. The primary male sex organs of the reproductive system are the testes. The other structures of the male reproductive system are termed accessory reproductive organs. The accessory organs include both internal and external reproductive organs. See figure 1-60 for an illustration of the male reproductive system.

Figure 1-60.-The male reproductive system.

TESTES
The testes, as stated earlier, are the primary male reproductive organs. They produce sperm cells (spermatozoa) and male hormones, both necessary for reproduction.

Structure
The testes are oval glands suspended inside a sac (the scrotum) by a spermatic cord. The spermatic cords are formed by the vas deferens, arteries, veins, lymphatics, and nerves, all bound together by connective tissue.

Each testis is encapsulated by a tough, white, fibrous tissue called the tunica albuginea. The interior of the testis is divided into 250 lobules (small lobes). Each lobule contains 1 to 4 highly coiled, convoluted tubules called seminiferous tubules. These tubules unite to form a complex network of channels called the rete testis. The rete testis give rise to several ducts that join a tube called the epididymis (fig. 1-60).

Functions
The testes perform two functions: to produce sperm cells and to secrete male sex hormones. The process by which sperm cells are produced is called spermatogenesis. Spermatogenesis occurs in the seminiferous tubules of the testes. Once the sperm cells are formed, they collect in the lumen of each seminiferous tubule. When the sperm cells are ready, they pass through the rete testis to the epididymis, where they remain for a time to mature. The production of sperm cells occurs continually throughout the reproductive life of a male.

The male hormone testosterone is produced in the testes. This hormone is initially responsible for the formation of the male reproductive organs. During puberty, testosterone stimulates the enlargement of the testes and various other accessory reproductive organs. It also causes the development of the male secondary sexual characteristics. Refer to the section titled "The Endocrine System" for more detailed discussion on male secondary sexual characteristics.

Other actions of testosterone include increasing the production of red blood cells. As a result, the average number of red blood cells in blood is usually greater in males than in females.