Chapter 13: Diagnostic tests
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Anatomy and physiology
Two of the three key functions of the male reproductive system are to produce and deliver sperm to the female ova for fertilization; the third is to produce and secrete male sex hormones in order to maintain the male reproductive system (Tortora and Derrickson [243]).
Spermatogenesis takes place in the testes in a constant and continuous cycle throughout an adult human male's life. On average, 300 million sperm complete spermatogenesis each day. Primary male germ cells are initially created in the outer wall of the germinal epithelium of the seminiferous tubules (Tortora and Derrickson [243]). As the sperm cells mature, they move into the lumen of the tubule to begin a circuitous journey through the male reproductive system. On this journey, sperm cells are augmented with nutritional and biochemical supplements, resulting in a greyish‐white viscous fluid (semen). Semen not only helps sperm to survive but also eases the transfer of sperm into the female reproductive tract and facilitates successful fertilization (Tortora and Derrickson [243]).
Components of normal semen
The volume of semen released per ejaculate varies between 2 and 5 mL. The average ejaculate is 3.4 mL. Semen contains:
- fructose‐rich fluid from the seminal vesicles (65–70%)
- secretions from the prostate gland containing enzymes, citric acid, lipids and acid phosphatase (25–30%)
- 200–500 million sperm (2–5%)
- secretions produced by the bulbourethral glands that aid the mobility of sperm in the vagina and cervix (1%) (Mandal [134]).
Semen is released during the two‐phase process of ejaculation. It is controlled by the central nervous system; ejaculation occurs when there is friction on the genitalia or other forms of sexual stimulation occur, leading to impulses that are sent via the spinal cord to the brain. Phase 1 occurs when the vas deferens contracts to squeeze the sperm towards the base of the penis through the prostate gland and into the urethra. The seminal vesicles release their part of the semen, which combines with the sperm (Mulhall [150], Tortora and Derrickson [243]).
Phase 2 is when the muscles at the base of the penis and urethra contract. This forces the semen out of the penis. During this phase, the bladder neck contracts to prevent the backflow of the semen into the urinary tract (if this occurs, it is called retrograde ejaculation). The final components of the semen join together in the posterior urethra and mix only after ejaculation (Mulhall [150], Tortora and Derrickson [243]).
