Friday, February 7, 2014

Prostate Anatomy


Location and Description
  • The prostate is a fibromuscular glandular organ that surrounds the prostatic urethra . It is about 1.25 in. (3 cm) long and lies between the neck of the bladder above and the urogenital diaphragm below.
  • The prostate is surrounded by a fibrous capsule. The prostate has a base, which lies  against the bladder neck above, and an apex, which lies against the urogenital diaphragm below. The two ejaculatory ducts pierce the upper part of the posterior surface of the prostate to open into the prostatic urethra at the lateral margins of the prostatic utricle.
Relations
  • Superiorly: The base of the prostate is continuous with the neck of the bladder, the smooth muscle passing without interruption from one organ to the other. The urethra enters the center of the base of the prostate.
  • Inferiorly: The apex of the prostate lies on the upper surface of the urogenital diaphragm. The urethra leaves the prostate just above the apex on the anterior surface.
  • Anteriorly: The prostate is related to the symphysis pubis, separated from it by the extraperitoneal fat in the retropubic space (cave of Retzius). The prostate is connected to the posterior aspect of the pubic bones by the fascial puboprostatic ligaments.
  • Posteriorly: The prostate is closely related to the anterior surface of the rectal ampulla and is  separated from it by the rectovesical septum (fascia of Denonvilliers). This septum is formed in fetal life by the fusion of the walls of the lower end of the rectovesical pouch of peritoneum, which originally extended down to the perineal body.
  • Laterally: The prostate is embraced by the anterior fibers of the levator ani as they run posteriorly from the pubis.
Structure of the Prostate
  • The numerous glands of the prostate are embedded in a mixture of smooth muscle and connective tissue, and their ducts open into the prostatic urethra.
  • The prostate is incompletely divided into five lobes. 
  • The anterior lobe lies in front of the urethra and is devoid of glandular tissue. 
  • The median, or middle, lobe is the wedge of gland situated between the urethra and the ejaculatory ducts. Its upper surface is related to the trigone of the bladder; it is rich in glands. 
  • The posterior lobe is situated behind the urethra and below the ejaculatory ducts and also contains glandular tissue. 
  • The right and left lateral lobes lie on either side of the urethra and are separated from one another by a shallow vertical groove on the posterior surface of the prostate. The lateral lobes contain many glands.
Function of the Prostate
  • The prostate produces a thin, milky fluid containing citric acid and acid phosphatase that is added to the seminal fluid at the time of ejaculation. 
  • The smooth muscle, which surrounds the glands, squeezes the secretion into the prostatic urethra. 
Blood Supply

Arteries
  • Branches of the inferior vesical and middle rectal arteries.

Veins
  • The veins form the prostatic venous plexus, which lies outside the capsule of the prostate. The prostatic plexus receives the deep dorsal vein of the penis and numerous vesical veins and drains into the internal iliac veins.

Lymph Drainage
  • Internal iliac nodes.

Nerve Supply
  • Inferior hypogastric plexuses. The sympathetic nerves stimulate the smooth muscle of the prostate during ejaculation.

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