In men over 50 enlargement of the prostate (benign prostatic hypertrophy) is common. Sometimes the result is pressure on the urethra and bladder, which interferes with urination, precipitating urinary retention and kidney disease. Balloon dilatation of the urethra and medication with alpha blockers, finasteride (Proscar), and extracts of saw palmetto have joined traditional surgical removal of the prostate (prostatectomy) as therapies. See also prostate cancer, prostatitis.
See J. P. Blandy and B. Lytton, The Prostate (1986).
Chestnut-shaped male reproductive organ, located under the bladder, which adds secretions to the sperm during ejaculation of semen. It surrounds the urethra (see urinary system) and is rounded at the top, narrowing to a blunt point. The prostate consists of 30–50 glands, supported by connective tissue, that discharge fluids into the urethra and two ejaculatory ducts. Those ducts, which also carry sperm and fluid discharged by the seminal vesicles, join the urethra inside the prostate. The prostate contributes 15–30percnt of the seminal fluid. It reaches its mature size at puberty. Around age 50, it commonly shrinks and decreases its secretions; an increase in size after midlife may be due to inflammation or malignancy. Seealso prostatic disorder.
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In human prostatic secretions, the protein content is less than 1% and includes proteolytic enzymes, prostatic acid phosphatase, and prostate-specific antigen. The secretions also contain zinc with a concentration 500-1,000 times the concentration in blood.
The main male hormone is testosterone, which is produced mainly by the testicles. Some male hormones are produced in small amounts by the adrenal glands. However, it is dihydrotestosterone that regulates the prostate.
The ducts are lined with transitional epithelium.
Within the prostate, the urethra coming from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts. (The male urethra has two functions: to carry urine from the bladder during urination and to carry semen during ejaculation.) The prostate is sheathed in the muscles of the pelvic floor, which contract during the ejaculatory process.
The prostate can be divided in two different ways: by zone, or by lobe.
The prostate gland has four distinct glandular regions, two of which arise from different segments of the prostatic urethra:
|Peripheral zone (PZ)||Composes up to 70% of the normal prostate gland in young men||The sub-capsular portion of the posterior aspect of the prostate gland which surrounds the distal urethra. It is from this portion of the gland that more than 64% of prostatic cancers originate.|
|Central zone (CZ)||Constitutes approximately 25% of the normal prostate gland||This zone surrounds the ejaculatory ducts. The central zone accounts for roughly 2.5% of prostate cancers although these cancers tend to be more aggressive and more likely to invade the seminal vesicles.|
|Transition zone (TZ)||Responsible for 5% of the prostate volume at puberty.||Prostate cancer originates in this zone in roughly 34% of patients. The transition zone surrounds the proximal urethra and is the region of the prostate gland which grows throughout life and is responsible for the disease of benign prostatic enlargement. (2)|
|Anterior fibro-muscular zone (or stroma)||Accounts for approximately 5% of the prostatic weight||This zone is usually devoid of glandular components, and composed only, as its name suggests, of muscle and fibrous tissue.|
The "lobe" classification is more often used in anatomy.
|Anterior lobe (or isthmus)||roughly corresponds to part of transitional zone|
|Posterior lobe||roughly corresponds to peripheral zone|
|Lateral lobes||spans all zones|
|Median lobe (or middle lobe)||roughly corresponds to part of central zone|
BPH can be treated with medication, a minimally invasive procedure or, in extreme cases, 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. 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.
Though prostate cancer is of most concern to older men, it is like other cancers, a complex disease with many risk factors; race, age, genetics, and lifestyle habits can all contribute to its development.
However, in March of the same year, the National Institute of Child Health and Human Development held a conference cosponsored by the National Cancer Institute and others to review the available data and information on the link between prostate cancer and vasectomies. It was determined that an association between the two was very weak at best, and even if having a vasectomy increased one's risk, the risk was relatively small.
In 1997, the NCI held a conference with the prostate cancer Progressive Review Group (a committee of scientists, medical personnel, and others). Their final report, published in 1998 stated that evidence that vasectomies help to develop prostate cancer was weak at best.