A semen sample consists of spermatozoa and seminal plasma, which is a mix of a number of secretions. These secretions come mainly from parts of the male reproductive system such as the epididymis, the prostate and the seminal vesicles.
If there is an obstruction at any point in the male reproductive system then the spermatozoa are not found in the ejaculate. Depending on the site of the blockage, the fluids secreted by the epididymis, the prostate and the seminal vesicles are also not found in the ejaculate. In order to detect the point of occlusion a number of marker molecules are used.
In particular, the presence of fructose, which originates from the seminal vesicles, α-glucosidase, which is secreted by the epididymis, and acid phosphatase, which originates from the prostate, are measured. For the prostate there are other marker molecules that give information about its functionality such as zinc, citric acid and magnesium. So the determination of these molecules is very useful in cases of obstruction.
The secretory activity of the accessory glands can also be affected by the presence of microorganisms. Infection can cause a temporary decease in the secretory activity but sometimes the decrease at the secretory epithelium can be irreversible and result at low quality semen sample. The measurement of the marker molecules such as fructose and acid phosphatase can access the function of the glands.