The testes, or testicles, have two major functions: the secretion of sex hormones and the production of sperm. The testes form inside the abdominal cavity, and late in fetal development they migrate through the inguinal canal from the abdomen to the scrotum (Kaftanovskaya et al., 2011).
At birth the testes are normally in the scrotum, but in some cases one or both fail to descend. This condition, known as cryptorchidism (krip-TOR-kuh-di-zum), meaning "hidden testis," affects 3-5% of male infants (Kollin et al., 2006). Undescended testes often move into place spontaneously sometime after birth. However, if they have not descended by age 6 months, the likelihood of spontaneous descent is small (Kelsberg et al., 2006). Recent research indicates that parental exposure to pesticides in the environment may contribute to cryptorchidism (Gaspari et al., 2011).
Parents should watch out for cryptorchidism, especially when both testes are affected. Sperm production is affected by temperature. Average scrotal temperature is several degrees lower than body temperature, and sperm production appears to be optimal at this lower temperature. Undescended testes remain at internal body temperature, which is too high for normal sperm production, and infertility could result (Dalgaard, 2012; Thorup et al., 2011). Cryptorchidism is also associated with an increased risk for developing testicular cancer (Dalgaard, 2012; Shaw, 2008). Surgical or hormonal treatment is sometimes necessary to correct this condition (Thorup et al., 2011).
In most men the testes are asymmetric. Note in Figure 4.3 that the left testis hangs lower than the right testis. This is usually the case because the left spermatic cord is generally longer than the right. It is no more unusual than a woman having one breast that is larger than the other. Our bodies simply are not perfectly symmetric.
It is important for men to become familiar with their testes and to examine them regularly. The testes can be affected by a variety of diseases, including cancer, sexually transmitted infections, and an assortment of other infections. (Diseases of the male sex organs are discussed at the end of this chapter and in Chapter 15.) Most of these conditions have observable symptoms, and early detection allows for rapid treatment; early detection can also prevent far more serious complications.
Unfortunately, most men do not regularly examine their testes. Yet this simple, painless, and potentially lifesaving process, which takes only a few minutes, is an excellent method for detecting early signs of disease. This procedure is described and illustrated in the Your Sexual Health box, "Male Genital Self-Examination" on page 94.
(b)
I Figure 4.5 (a) Internal structure of a testis. Sperm are produced in the seminiferous tubules and transported to the epididymis, which serves as a storage chamber. (b) the cross-section enlargement view of the seminiferous tubules shows spermatogenic (sperm-making) cells and the interstitial cells.
Male Sexual Anatomy and physiology
YOUR SEXUAL
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