Prostate Gland

Prostate Gland Definition

The prostate is a gland set between the bladder and the penis in human males. The skene’s gland in the vagina is considered the female homolog of the prostate gland, but for simplicity’s sake we will focus on men.

The prostate is about the size of a walnut, or 1.5 in, and is penetrated by the urethra that directs urine out of the body. During ejaculation, the prostate will expel an alkaline seminal fluid into the urethra. The alkaline nature of semen counters the acidic environment of the vagina. This protects sperm, and prolongs the time in which sperm can be motile in the vaginal tract. The prostate gland also relies on muscle to help eject the sperm.

Prostate
Illustrated in the picture is the prostate gland and neighboring organs.

Prostate Gland Structure

The prostate is the largest accessory gland in males. It is found inferior to the neck of the bladder, and above the urethral sphincter (as pictured in the illustration). Moreover, the prostate lies in front of the rectum, making it easy for physicians to conduct digital rectal exams (DRE) to inspect the health of the gland. The prostate’s proteolytic enzymes are able to exit the prostate through ducts that open into the urethra prior to ejaculating. Furthermore, the prostate gland can be divided into four anatomical lobes. But a more significant delineation is a histological parsing into zones.

  • The central zone is the area that surrounds the ejaculation ducts. It derives from the Wolffian duct in human embryos.
  • The transitional zone is the area near the center that surrounds the urethra. It derives from the urogenetical sinus.
  • The peripheral zone forms the body of the prostate gland. This area is located toward the back, and derives from the urogenital sinus.

The prostate gland is notably vascular and well-innervated. The arterial supply, or oxygen rich blood, of the prostate comes from the prostatic arteries. In contrast, oxygen-depleted blood drains into the prostatic venous plexus and enters the iliac veins of the pelvis. The innervation of the prostate gland is a little simpler. The prostate gland is innervated by the inferior hypogastric nerve plexus. A plexus is more or less a bundle of nerves that innervate the smooth muscle of the prostate.

Prostate Gland Function

Prostate glands have the primary function of secreting prostate fluid. Prostate fluid is a part of the seminal fluid that is ejected during ejaculation after sex. The prostate muscles will help eject the seminal fluid into the urethra. The muscles themselves weigh about twenty grams, and surround the urethra just below the bladder. During ejaculation, sperm is shuttled through drainage tubes called the vas deferens and into the site of the prostate gland. Once this happens, the prostate squeezes, with the help of its surrounding muscles, and closes the opening that is found between the urethra and bladder. This directs the fluid into the urethra and pushes the semen out. The seminal fluid itself is composed of citric acid, enzymes, and zinc. While the prostate fluid is slightly acidic, the fluid produced by seminal vesicles makes the semen slightly basic – which, as mentioned before, is a protective measure to prolong their lifespan. Another element in prostate fluid is an enzyme, PSA or prostate specific agent. PSA plays a role in liquefying seminal fluid to allow sperm to swim easily. A physician can order a blood test to measure the levels of PSA in the patient’s blood. When PSA levels are high, the presence of prostate cancer is likelier. The site of the prostate makes it a great location for delivering fluid; however, it also makes it an easier target of affliction when the gland swells.

Prostate Gland Pathology

A swollen prostate gland will press against the urethra and at least partially block urination. This will irritate the bladder and the surrounding area. In fact, urinary discomfort secondary to gland swelling is a frequent occurrence in older gentlemen. Up to half of men over the age of sixty suffer from Benign Prostatic Hyperplasia (BPH), or an enlarged prostate gland. This statistic jumps to ninety percent between the ages of seventy and eighty. The symptoms of this affliction include frequent urination and leaking. Treatment for an enlarged prostate can include alpha blockers to relax the muscles around the urethra, and 5-alpha reductase inhibitors to shrink the prostate secondary to reducing the levels of DHT testosterone. Likewise, prostatitis is another condition where an infection inflames the prostate tissue. This is treated with a round(s) of antibiotics. But not all prostate growth is benign.

It is estimated that over 200,000 men are diagnosed with prostate cancer each year, per the National Cancer Institute. The five-year survival rate for men diagnosed with prostate cancer is merely 29 percent. So, a little under 30,000 deaths are caused by this disease each year. Prostate cancer takes third place in the leading causes of death in American men. A combination of surgery, radiation, and chemotherapy is used to treat prostate cancer, as researchers continue to search for a cure.

Quiz

1. Which of the following is the main role of the prostate?
A. Sperm production
B. Alkalize seminal fluid
C. Expel seminal fluid
D. Cleanse the vas deferens

Answer to Question #1
D is correct.

2. What is the role of PSA in the male body?
A. Thickens the semen
B. Expands the prostate gland
C. Thins the semen
D. Contract the prostate gland

Answer to Question #2
C is correct. PSA is a protein that is a great indicator of prostate health, where high levels correlate with a higher likelihood of developing prostate cancer. Its role in the body is to liquefy, or thin, seminal fluid so that sperm can swim freely.

References

  • Hoffman, Matthew MD (2017). “Picture of the Prostate.” WebMD: human anatomy. Retrieved on 2017-06-21 from http://www.webmd.com/urinary-incontinence-oab/picture-of-the-prostate#2
  • eMedicine Health (2017). “Enlarged Prostate (Beginning Prostate Hyperplasia or BPH).” <eMedicineHealth. Retrieved on 2017-06-21 from http://www.emedicinehealth.com/enlarged_prostate/article_em.htm
  • MedicineNet (2017). “Medical Definitoin of Prostate Gland.” Retrieved on 2017-06-21 from http://www.medicinenet.com/script/main/art.asp?articlekey=5073
  • Teach Me Anatomy (2017). “The Prostate Gland.” Retrieved on 2017-06-22 from http://teachmeanatomy.info/pelvis/the-male-reproductive-system/prostate-gland/
  • Cancer.Net Editorial Board (2017). Prostate Cancer: Statistics. Cancer.Net. Retrieved on 2017-06-22 from http://www.cancer.net/cancer-types/prostate-cancer/statistics
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