Prostate, its function and disease.

The sexual accessory glands

The sexual accessory glands are exocrine glands and consists of the seminal vesicles, the prostate, and Cowper's glands( bulbourethral gland).
All of them are involve in maintaining the viabilty and motility of the sperm to ensure successful fertilization.
95% of ejaculatory fluid originates from the accessory glands and not from the testes.
In a normal human male's ejaculate volume ranging from 2-6 ml. Largest portion is secreted by the seminal vesicle.
Ejaculate is a rich source of protiens and enzymes as well as hghly bioreactive components such as prostaglandins, spermine, and fructose.
The growth and functioning of this glands depends on the androgens produce by the testes.

Stucture of the prostate

Small gland the size of a walnut and weighs approximately 25g. It is located at the base of the bladder and surrounds the urethra.
The vas deferens joins the duct from seminal vesicles and becomes the ejaculatory duct that courses through the structure of the prostate.
There are 15-30 excretory ducts from the prostate entering the urethra as it passes through the prostate. This part of urethra is called the prostatic urethra.
Each of this excretory ducts receives prostatic secretions from 4-6 prostatic lobules that containing prostatic acini. They are lined by tall columnar epithelium.
During ejaculation, nerves to the prostate from the hypogastric plexus, under sympathetic stimulation, cause muscular contraction of the prostate and excretion of the acinar contents into the ducts and out through the urethra and penis to form the ejaculate.


Role of androgen in the prostate

Androgens has a role in growth of the prostate and formation of prostatic secretion.
Testosterone synthesized in the leydig cells of the testes under influence of Luteinizing hormone (LH) stimulation, enters the serum, is complexed to a steroid binding globulin and is transported to the prostate. It then diffuses across the epithelial and stromal cell membranes and enters the prostatic cells.
The testosterone is then metabolized to more androgenic substance call dihydrotestosterone(DHT) by 5-Alpha reductase.
The stromal and epithelial cells also excrete highly insoluble components forming the extracellular matrix and basement membrane that creates a physical interference and solid state support between the prostate epithelial and stromal components.

Prostate gland disease

Androgens (testosterone and related hormones) are considered to play a important role in BPH . This means that androgens have to be present for BPH to occur, but do not necessarily directly cause the condition.

This is supported by the fact that castrated boys do not develop BPH when they age, unlike intact men. Additionally, administering exogenous testosterone is not associated with a significant increase in the risk of BPH symptoms.
Dihydrotestosterone (DHT), a metabolite of testosterone is a critical mediator of prostatic growth. This enzyme is localized principally in the stromal cells; hence, these cells are the main site for the synthesis of DHT.

DHT can act in an autocrine fashion on the stromalie cells or in paracrine fashion by diffusing into nearby epithelial cells. In both of these cell types, DHT binds to nuclear androgen receptors and signals the transcription of growth factors that are mitogenic to the epithelial and stromal cells. DHT is 10 times more potent than testosterone because it dissociates from the androgen receptor more slowly. The importance of DHT in causing nodular hyperplasia is supported by clinical observations in which an inhibitor of 5α-reductase is given to men with this condition. Therapy with 5α-reductase inhibitor markedly reduces the DHT content of the prostate and in turn reduces prostate volume and, in many cases, BPH symptoms.

There is evidence showing that estrogens play a role in the etiology of BPH. The fact that BPH occurs when men generally have elevated estrogen levels and relatively reduced free testosterone levels, and when prostate tissue becomes more sensitive to estrogens and less responsive to DHT. Cells taken from the prostates of men who have BPH have been shown to grow in response to high estradiol levels with low androgens present. Estrogens may render cells more susceptible to the action of DHT.

On a microscopic level, BPH can be seen in the vast majority of men as they age, particularly over the age of 70 years, around the world. However, rates of clinically significant, symptomatic BPH vary dramatically depending on lifestyle. Men who lead a western lifestyle have a much higher incidence of symptomatic BPH than men who lead a traditional or rural lifestyle. This is confirmed by research in China showing that men in rural areas have very low rates of clinical BPH, while men living in cities adopting a western lifestyle have a increase incidence of this condition, though it is still below rates seen in the West.


Lifestyle Modifications
Patients should decrease fluid intake before bedtime, moderate the consumption of alcohol and caffeine-containing products, and follow timed voiding schedules.

Medical methods
Alpha blockers (α1-adrenergic receptor antagonists) provide symptomatic relief of BPH symptoms. Available drugs include doxazosin, terazosin, alfuzosin and tamsulosin. Older drugs, phenoxybenzamine and prazosin are not recommended for treatment of BPH. Alpha-blockers relax smooth muscle in the prostate and the bladder neck, and decrease the degree of blockage of urine flow. Alpha-blockers may cause ejaculation back into the bladder (retrograde ejaculation).

The 5α-reductase inhibitors (finasteride and dutasteride) are another treatment option. When used together with alpha blockers a reduction of BPH progression to acute urinary retention and surgery has been noted in patients with larger prostates.

Though former research indicated the efficacy of Serenoa repens (saw palmetto) fruit extracts in alleviating mild-to-moderate BPH symptoms,a recent double-blind study did not demonstrate any efficacy greater than that of a placebo for moderate-to-severe symptoms.Herbal medicines that have research support in systematic reviews include beta-sitosterol from Hypoxis rooperi (African star grass) and pygeum (extracted from the bark of Prunus africana), while there is less substantial support for the efficacy of Cucurbita pepo (pumpkin) seed and Urtica dioica (stinging nettle) root.At least one double-blind trial has also supported the efficacy of rye flower pollen.

Sildenafil shows some symptomatic relief, suggesting a possible common etiology with erectile dysfunction.

If medical treatment fails, transurethral resection of prostate (TURP) surgery may need to be performed. This involves removing (part of) the prostate through the urethra. There are also a number of new methods for reducing the size of an enlarged prostate, some of which have not been around long enough to fully establish their safety or side effects. These include various methods to destroy or remove part of the excess tissue while trying to avoid damaging what's left. Transurethral electrovaporization of the prostate (TVP), laser TURP, visual laser ablation (VLAP), TransUrethral Microwave ThermoTherapy (TUMT), TransUrethral Needle Ablation (TUNA), ethanol injection, and others are studied as alternatives.

Newer techniques involving lasers in urology have emerged in the last 5-10 years. Starting with the VLAP technique involving the Nd:YAG laser with contact on the prostatic tissue. A similar technology called Photoselective Vaporization of the Prostate (PVP) with the GreenLight (KTP) laser have emerged very recently. This procedure involves a high powered 80 Watt KTP laser with a 550 micrometre laser fiber inserted into the prostate. This fiber has an internal reflection with a 70 degree deflecting angle. It is used to vaporize the tissue to the prostatic capsule. KTP lasers target haemoglobin as the chromophore and typically have a penetration depth of 2.0mm (four times deeper than holmium).

Another procedure termed Holmium Laser Ablation of the Prostate (HoLAP) has also been gaining acceptance around the world. Like KTP the delivery device for HoLAP procedures is a 550um disposable side-firing fiber that directs the beam from a high powered 100 Watt laser at a 70degree from the fiber axis. The holmium wavelength is 2,140nm, which falls within the infrared portion of the spectrum and is invisible to the naked eye. Where KTP relies on haemoglobin as a chromophore, water within the target tissue is the chromophore for Holmium lasers. The penetration depth of Holmium lasers is <0.5mm avoiding complications associated with tissue necrosis often found with the deeper penetration and lower peak powers of KTP.

Both wavelengths, KTP and Holmium, ablate approximately one to two grams of tissue per minute.

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