The human urinary tract is composed of two main organs: the kidneys, which are the organs in charge of producing urine, and the bladder, where urine is stored to later be released through the urethra.The ureters transport urine from the kidneys to the bladder.

The process of urination
Once the bladder has been filled (250-500 ml) the nerves supplying the bladder send a signal to the brain that produces the desire to urinate.Urination begins with contraction of the muscle of the bladder and the relaxation of the sphincters (closing mechanisms) situated at the neck of the bladder and the urethra, permitting the exit of urine through the urinary meatus (the external orifice of the urethra).

What is the prostate?
The prostate is a sexual accessory gland of the male reproductive system that, in an adult male, is similar in size and shape to a chestnut, weighing between approximately 12 and 20 grams.It is situated below the bladder at the beginning of the urethra, behind the pubic bone and in front of the anal canal.Its structure is similar to a sponge, formed by thousands of small cavities where prostatic secretions are formed and then emptied into the prostatic urethra via dozens of small channels.

In 1953 the Spanish urologist Salvador Gil Vernet demonstrated that the prostate gland is not homogeneous and is actually composed of three well differentiated zones: the cranial zone and the intermediate zone, where benign growth occurs, and the caudal zone, the primary site of malignant growth.

Its development and growth, which begins in puberty, is controlled by male sexual hormones (testosterone).All mammals have a prostate, but the pathologic processes of benign hyperplasia and cancer develop only in humans and canines.

What is the purpose of the prostate?
The prostate gland produces a secretion that constitutes 25% of the volume of semen, which fuels and protects spermatozoa.The secretion is primarily made up of enzymes such as prostate specific antigen (or PSA), zinc, prostaglandins, and citrates.During ejaculation the prostate contracts and, releases its secretions through collection ducts into the prostatic urethra, where the fluid is mixed with secretions from the seminal vesicles and the ductus deferens to form semen. The prostate therefore clearly has a very important role in fertility, and any pathologic process that can damage it will affect male reproductive capacity.

Diseases of the prostate
The most common diseases are benign prostatic hyperplasia, prostate cancer and acute or chronic prostatitis.