Prostate

The prostate (from Ancient Greek προστάτης, prostátēs, literally 'one who stands before', 'protector', 'guardian') is an exocrine gland of the male reproductive system in most mammals. It differs considerably among species anatomically, chemically, and physiologically. Anatomically, the prostate can be subdivided in two ways: by zone or by lobe. It does not have a capsule; rather an integral fibromuscular band surrounds it. It is sheathed in the muscles of the pelvic floor, which contract during the ejaculatory process. The prostate also contains some smooth muscles that also help expel semen during ejaculation. The function of the prostate is to secrete a fluid which contributes to the volume of the semen. This prostatic fluid is slightly alkaline, milky or white in appearance, and in humans usually constitutes roughly 30% of the volume of semen, the other 70% being spermatozoa and seminal vesicle fluid. The alkalinity of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm. The prostatic fluid is expelled in the first part of ejaculate, together with most of the sperm. In comparison with the few spermatozoa expelled together with mainly seminal vesicular fluid, those in prostatic fluid have better motility, longer survival, and better protection of genetic material. Disorders of the prostate include enlargement, inflammation, infection, and cancer. The classical description of a healthy human male prostate portrays it as slightly larger than a walnut. The mean weight of the normal prostate in adult males is about 11 grams, usually ranging between 7 and 16 grams. The volume of the prostate can be estimated by the formula 0.52 × length × width × height. A volume of over 30 cm3 is regarded as prostatomegaly (enlarged prostate). A study stated that prostate volume among patients with negative biopsy is related significantly with weight and height (body mass index), so it is necessary to control for weight. The prostate surrounds the urethra just below the urinary bladder and can be felt during a rectal exam. The secretory epithelium is mainly pseudostratified, comprising tall columnar cells and basal cells which are supported by a fibroelastic stroma — containing randomly oriented smooth-muscle bundles — that is continuous with the bladder. The epithelium is highly variable and areas of low cuboidal or squamous epithelium are also present, with transitional epithelium in the distal regions of the longer ducts.Within the prostate, the urethra coming from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts. Three histological types of cells are present in the prostate gland: glandular cells, myoepithelial cells, and subepithelial interstitial cells. One can sub-divide the prostate in two ways: by zone or by lobe. It does not have a capsule; rather an integral fibromuscular band surrounds it. It is sheathed in the muscles of the pelvic floor, which contract during the ejaculatory process.