Prostate

Prostate is a glandular organ, fibromuscular in nature, which surrounds the prostatic part of urethra. It lies between the neck of the bladder above and the urogenital diaphragm below. It is about 1.5 inches long and has somewhat conical shape, surrounded by a fibrous capsule.

The base of the prostate lies against the neck of urinary bladder and its apex lies against the urogenital diaphragm. The urethra enters the center of the base of prostate and leaves it just above the apex. The posterior surface is pierced by the two ejaculatory ducts, which open into the prostatic urethra at the lateral margins of the prostatic utricle.

Internal structure:

The small glands of prostate, which produce the secretions, are embedded in a mixture of smooth muscle and connective tissue with no definite order. The ducts of these small glands open into the prostatic part of urethra.

Internally, the prostate is incompletely divided into five lobes, as described below:

  • Anterior lobe:  It lies in front of the prostatic urethra and is devoid of secretory glands.
  • Middle lobe: It is a wedge-shaped lobe situated between the urethra and the ejaculatory ducts. It is rich in glands.
  • Posterior lobe: It is situated behind the urethra and below the ejaculatory ducts. It is also rich in glands.
  • Left and right lateral lobes: These are situated on the corresponding side of urethra and are separated from one another by a shallow groove. Both these lobes contain many glands.

Important relations:

Anterior:

  • Symphysis pubis, from which prostate is separated by extraperitoneal fat
  • Posterior aspect of pubic bones, to which the prostate is connected by puboprostatic ligaments

Posterior:

  • Anterior surface of the rectal ampulla

Lateral:

  • Anterior fibers of levator ani

Superior:

  • Neck of bladder

Inferior:

  • Urogenital diaphragm

Functions:

As described above, prostate is a glandular organ. It produces a thin, milky fluid containing citric acid and acid phosphatase. Overall, the prostatic secretions are alkaline and are necessary to neutralize the acidity in the vagina and thus protect the sperm from denaturation.

At the time of ejaculation, the smooth muscle surrounding the small glands of prostate contracts. This squeezes the secretion into the prostatic urethra where it is mixed with the seminal fluid.

Blood supply:

Arterial supply is provided by branches of the inferior vesical and middle rectal arteries. Venous drainage is by way of small veins that form prostatic venous plexus, lying outside the capsule. In addition to small prostatic veins, the plexus also receives deep dorsal vein of penis and numerous vesical veins. The plexus drains into the internal iliac veins.

Lymph drainage:

Lymph from the prostate is drained into the internal iliac nodes.

Nerve supply:

Inferior hypogastric plexus supplies the nerve fibers to innervate prostate. Sympathetic stimulation causes smooth muscles to contract and thus squeezes the secretions out during ejaculation.