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male body

The male reproductive system consists of three main parts:

  • Testicles
  • Epididymis
  • Vas deferens (sperm ducts)
male reproductive system

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testicles (testes)

The two testicles, normally about four to five centimetres long, are found in the scrotum (a structure made up of multiple layers of muscles which protect the testicles and help control their temperature). The testicles have two very important functions, both of which are essential for normal male fertility: the first is the production of the male hormone testosterone; and, the second is the production of sperm cells (spermatozoa). The development of sperm starts in the testicles. From here, they travel to the epididymis.

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epididymis

The epididymis is a long, narrow spiral-shaped tube surrounded by a layer of connective tissue. Rolled out, the epididymis would be approximately six meters long! The epididymis is found at the back of the testicles and is divided into a head, body and tail. Here the sperm undergoes its final development and maturation, and is stored until ejaculation. From the epididymis, the sperm travels to the vas deferens (sperm ducts).

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vas deferens

The vas deferens or sperm ducts have a long, tube-shaped structure that connects the epididymis (where the sperm is stored) with the urinary tract (through which the sperm is discharged). While the urinary tract - as the name suggests - also releases urine, the presence of a valve prevents the simultaneous discharge of sperm and urine. During ejaculation, the sperm streams from the testicles through the vas deferens into the urinary tract. As the sperm leaves the body via the penis, the prostrate and other glands add seminal fluids.

When a male is sterilised, both vas deferens are severed so that sperm can no longer enter the urinary tract and are not present in the ejaculate.

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sperm cells (spermatozoa)

The ejaculate mostly contains fluid originating from the prostrate and the sperm fluid creators, as well as millions of sperm cells. Both the quantity and the quality of the sperm cells are critical when it comes to fertilisation. In the laboratory, the ejaculate can be examined for numerous characteristics including:

  • The volume of ejaculate (in millilitres, 2 - 5 ml)
  • Concentration of sperm cells (number/ml)
  • Mobility of sperm cells
  • Number of living sperm cells
  • Appearance of sperm cells
  • Agglutination or clotting together of sperm cells

The World Health Organisation (WHO) has created criteria for a “normal” result (normospermic).

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normal male reproductive physiology

The production of sperm - a process termed spermatogenesis - is a highly complicated process that begins during puberty and continues, in healthy men, until death. The process starts in the testicles and is regulated by various hormones. These hormones are in turn regulated by the hypothalamus and the pituitary gland in the brain.

The hypothalamus controls the hormonal activity of the pituitary through secretion of gonadotropin-releasing hormone (GnRH). This hormone in turn controls the production of the gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH) by the pituitary. LH activates the production of testosterone (a hormone essential for sperm production), while FSH also activates other hormones that assist in the production of sperm. Besides sperm production, testosterone is also responsible for virility, male hair growth and muscle growth.

From start to finish, the production of sperm takes approximately 72 days. For the first 50 days, the sperm remains within the testicles moving into the epididymis for the remainder of this time. In the epididymis, the sperm mature and gain their mobility (the ability to swim). During sexual intercourse, the sperm is ejaculated into the female reproductive tract via the vagina and commences its journey (of approximately 12cm) through the cervix and the womb to the Fallopian tubes, the site of fertilisation. On the way, there are many cavities, folds or ‘wrong turnings’ that prevent many sperm cells from reaching their final destination. This explains why so many sperm cells - millions - are needed to achieve fertilisation.

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