Infertility is defined as the failure to conceive after one year of unprotected intercourse. Approximately 15% of couples attempting their first pregnancy meet with failure. About 50% of couples seeking treatment will have a male factor as the underlying cause of the infertility. It is therefore important that both partners are seen and investigated together.
There have been great technological advances in the development and success of assisted conception in the last two decades. This means that many couples with infertility can now be offered treatment.
The hypothalamus (a gland in the brain which links the central nervous system to the endocrine system via the pituitary gland) responds to a variety of signals from the central nervous system, pituitary and testicles to release GnRH (gonadatrophin releasing hormone). GnRH stimulates the pituitary gland to release LH (luteinising hormone) and FSH (follicle stimulating hormone). The testicle contains Leydig cells and Sertoli cells. The Leydig cells respond to LH by producing testosterone. Testosterone produces secondary sexual characteristics in men, such as the deep voice and facial and body hair. It also stimulates sperm production and development. The Sertoli cells respond to FSH to become involved in the maturation of germ cells, which will become spermatozoa. Spermatogenesis refers to the six stage process of the germ cells developing into spermatozoa. The cycle of spermatogenesis takes 74 days.
Spermatozoa in the testicle are non-motile. As they progress through the epididymis they gain progressive motility and fertilizing ability. The epididymis also acts as a storage area for sperm and transports the sperm to the vas deferens. The contents of the vas are propelled into the ejaculatory duct. From here the sperm is deposited into the posterior urethra (water-pipe), together with secretions from the seminal vesicles and prostate. When the fluid is ejaculated the first portion is rich in sperm. Fluid from the seminal vesicles and prostate provide nourishment for the sperm as well as acting with a buffering effect on the acidic vaginal environment.
Fertilisation usually takes place within the uterine tubes after ovulation has occurred. Due to various changes and interactions the fertilising sperm cell is able to reach the oocyte, traverse its various layers and become incorporated into the ooplasm of the egg.