Male Fertility

The approximate volume of semen for each ejaculation is 1.5 to 5.0 milliliters. The bulk of this fluid (45% to 80%) is produced by the seminal vesicles, and 15% to 30% is contributed by the prostate. There are usually between 60 and 150 million sperm per milliliter of ejaculate. Normal human semen values are summarized in table 20.5.

A sperm concentration below about 20 million per milliliter is termed oligospermia (oligo = few) and is associated with decreased fertility. A total sperm count below about 50 million per ejaculation is clinically significant in male infertility. Oligospermia may be caused by a variety of factors, including heat from a sauna or hot tub, various pharmaceutical drugs, lead and arsenic poisoning, and such illicit drugs as marijuana, cocaine, and anabolic steroids. It may be temporary or permanent. In addition to low sperm counts as a cause of in fertility, some men and women have antibodies against sperm antigens (this is very common in men with vasectomies). While such antibodies do not appear to affect health, they do reduce fertility.

Attempts have been made to develop new methods of male contraception. These have generally involved compounds that suppress gonadotropin secretion, such as testosterone or a combination of progesterone and a GnRH antagonist. Another compound, gossy-pol, which interferes with sperm development, has also been tried. These drugs can be effective but have unacceptable side effects. One of the most widely used methods of male contraception is a surgical procedure called a vasectomy (fig. 20.24). In this procedure, each ductus (vas) deferens is cut and tied or, in some cases, a valve or similar device is inserted. A vasectomy interferes with sperm transport but does not directly affect the secretion of andro-gens from Leydig cells in the interstitial tissue. Since spermatogen-esis continues, the sperm produced cannot be drained from the

Parasympathetic -

axon

-Parasympathetic axon

Nitric Oxide Action

close Erection

■ Figure 20.23 Role of nitric oxide in penile erection and the action of Viagra. Nitric oxide is released as a neurotransmitter by particular parasympathetic axons, and is secreted as a paracrine regulator by endothelial cells of vessels in the penis (eNOS = endothelial nitric oxide synthase). Nitric oxide stimulates the production of cyclic GMP (cGMP), which serves as the intracellular second messenger in the mechanism of smooth muscle relaxation that leads to erection. The enzyme phosphodiesterase (PDE) breaks down cGMP, and it is this enzyme that is inhibited by the drug sildenafil (Viagra).

Oligospermic Mane And Enzymes Levels

Table 20.5 Semen Analysis

Characteristic

Reference Value

Volume of ejaculate

1.5-5.0 ml

Sperm count

40-250 million/ml

Sperm motility

Percentage of motile forms:

1 hour after ejaculation

70% or more

3 hours after ejaculation

60% or more

Leukocyte count

0-2,000/ml

pH

7.2-7.8

Fructose concentration

150-600 mg/100 ml

Source: Modified from L. Glasser, "Seminal Fluid and Subfertility," Diagnostic Medicine, July/August 1981, p. 28. Used by permission.

Source: Modified from L. Glasser, "Seminal Fluid and Subfertility," Diagnostic Medicine, July/August 1981, p. 28. Used by permission.

■ Figure 20.24 A vasectomy. In this surgical procedure a segment of the ductus (vas) deferens is removed through an incision in the scrotum.

testes and instead accumulate in "crypts" that form in the seminiferous tubules, epididymis, and ductus deferens. These crypts present sites for inflammatory reactions in which spermatozoa are phago-cytosed and destroyed by the immune system. It is thus not surprising that approximately 70% of men with vasectomies develop antisperm antibodies. These antibodies do not appear to cause autoimmune damage to the testes, but they do significantly diminish the possibility of reversing a vasectomy and restoring fertility.

Chapter Twenty

Dealing With Impotence Naturally

Dealing With Impotence Naturally

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Responses

  • charlie hugley
    Which food increase sperm volume?
    1 year ago

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