The function of the prostate is to secrete a slightly alkaline fluid, milky or white in appearance, that in humans usually constitutes roughly 30% of the volume of the semen along with spermatozoa and seminal vesiclefluid. Semen is made alkaline overall with the secretions from the other contributing glands, including, at least, the 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 ejaculate fractions, together with most of the spermatozoa. In comparison with the few spermatozoa expelled together with mainly seminal vesicular fluid, those expelled in prostatic fluid have better motility, longer survival and better protection of the genetic material.

The prostate also contains some smooth muscles that help expel semen during ejaculation.

Structure

A healthy human male prostate is classically said to be 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. A study stated that prostate volume among patients with negative biopsy is related significantly to 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 fibroblastic stroma containing randomly oriented smooth muscle bundles that's 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.

The prostate can be divided 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.

Male sexual response

During male ejaculation, sperm is transmitted from the ductus deferens into the male urethra via the ejaculatory ducts, which lie within the prostate gland. It is possible for some men to achieve orgasm solely through stimulation of the prostate gland, such as prostate massage or receptive anal intercourse.

Secretions

Prostatic secretions vary among species. They are generally composed of simple sugars and are often slightly alkaline. In human prostatic secretions, the protein content is less than 1% and includes proteolytic enzymes, prostatic acid phosphatase, beta-microseminoprotein, and prostate-specific antigen. The secretions also contain zinc with a concentration 500–1,000 times the concentration in blood.

Regulation

To function properly, the prostate needs male hormones (androgens), which are responsible for male sex characteristics. The main male hormone is testosterone, which is produced mainly by the testicles. It is dihydrotestosterone (DHT), a metabolite of testosterone, that predominantly regulates the prostate.

Inflammation

Prostatitis is inflammation of the prostate gland. There are primarily four different forms of prostatitis, each with different causes and outcomes. Two relatively uncommon forms, acute prostatitis, and chronic bacterial prostatitis, are treated with antibiotics (category I and II, respectively). Chronic non-bacterial prostatitis or male chronic pelvic pain syndrome (category III), which comprises about 95% of prostatitis diagnoses, is treated by a large variety of modalities including alpha-blockers, phytotherapy, physical therapy, psychotherapy, antihistamines, anxiolytics, nerve modulators, surgery, and more. More recently, a combination of trigger point and psychological therapy has proved effective for category III prostatitis as well. Category IV prostatitis, relatively uncommon in the general population, is a type of leukocytosis.

Benign Prostatic Hyperplasia

Benign prostatic hyperplasia (BPH) occurs in older men; the prostate often enlarges to the point where urination becomes difficult. Symptoms include needing to urinate often (frequency) or taking a while to get started (hesitancy). If the prostate grows too large, it may constrict the urethra and impede the flow of urine, making urination difficult and painful and, in extreme cases, completely impossible.

BPH can be treated with medication, a minimally invasive procedure, or, in extreme cases, a surgery that removes the prostate. Minimally invasive procedures include transurethral needle ablation of the prostate (TUNA) and transurethral microwave thermotherapy (TUMT). These outpatient procedures may be followed by the insertion of a temporary prostatic stent, to allow normal voluntary urination, without exacerbating irritative symptoms.

The surgery most often used in such cases is called transurethral resection of the prostate (TURP or TUR). In TURP, an instrument is inserted through the urethra to remove prostate tissue that is pressing against the upper part of the urethra and restricting the flow of urine. TURP results in the removal of mostly transitional zone tissue in a patient with BPH. Older men often have corpora amylacea (amyloid), dense accumulations of calcified proteinaceous material, in the ducts of their prostates. The corpora amylacea may obstruct the lumens of the prostatic ducts and may underlie some cases of BPH.

Urinary frequency due to bladder spasm, common in older men, may be confused with prostatic hyperplasia. Statistical observations suggest that a diet low in fat and red meat and high in protein and vegetables, as well as regular alcohol consumption, could protect against BPH.

Lifestyle changes to improve the quality of urination include urinating in the sitting position. This reduces the amount of residual volume in the bladder, increases the urinary flow rate, and decreases the voiding time.

Cancer

Prostate cancer is one of the most common cancers affecting older men in developed countries and a significant cause of death for elderly men (estimated by some specialists at 3%). Despite this, the American Cancer Society's position regarding early detection is "Research has not yet proven that the potential benefits of testing outweigh the harms of testing and treatment". They believe "that men should not be tested without learning about... the risks and possible benefits of testing and treatment" which should be discussed with a doctor at age 50 or at age 45 if the patient is black or has a father or brother who acquired prostate cancer before age 65. If checks are performed, they can be in the form of a physical rectal exam, measurement of prostate-specific antigen (PSA) level in the blood, or checking for the presence of the protein Engrailed-2 (EN2) in the urine.

Co-researchers Hardev Pandha and Richard Morgan published their findings regarding checking for EN2 in urine in the 1 March 2011 issue of the journal Clinical Cancer Research. A laboratory test currently identifies EN2 in urine, and a home test kit is envisioned similar to a home pregnancy test strip. According to Morgan, "We are preparing several large studies in the UK and in the US and although the EN2 test is not yet available, several companies have expressed interest in taking it forward."