Prostate
The prostate is a fibromuscular glandular organ that
surrounds the prostatic urethra. It is about1.25 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 somewhat conical 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.
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. The prostatic secretion is alkaline and
helps neutralize the acidity in the vagina.
Prostate
Examination
The prostate can be examined clinically by palpation by
performing a rectal examination. The examiner’s gloved finger can feel the
posterior surface of the prostate through the anterior rectal wall.
Prostate
Activity and Disease
It is now generally believed that the normal glandular
activity of the prostate is controlled by the androgens and estrogens
circulating in the bloodstream. The secretions of the prostate are poured into
the urethra during ejaculation and are added to the seminal fluid. Acid
phosphatase is an important enzyme present in the secretion in large amounts.
When the glandular cells producing this enzyme cannot discharge their secretion
into the ducts, as in carcinoma of the prostate, the serum acid phosphatase level
of the blood rises. It has been shown that trace amounts of proteins produced specifically
by prostatic epithelial cells are found in peripheral blood. In certain
prostatic diseases, notably cancer of the prostate, this protein appears in the
blood in increased amounts. The specific protein level can be measured by a
simple laboratory test called the PSA test
Benign
Enlargement of the Prostate
Benign enlargement of the prostate is common in men older than
50 years. The cause is possibly an imbalance in the hormonal control of the
gland. The median lobe of the gland enlarges upward and encroaches within the
sphincter vesicae, located at the neck of the bladder. The leakage of urine into
the prostatic urethra causes an intense reflex desire to micturate. The
enlargement of the median and lateral lobes of the gland produces elongation
and lateral compression and distortion of the urethra so that the patient
experiences difficulty in passing urine and the stream is weak. Back-pressure effects
on the ureters and both kidneys are a common complication. The enlargement of
the uvula vesicae (owing to the enlarged median lobe) results in the formation
of a pouch of stagnant urine behind the urethral orifice within the bladder.
The stagnant urine frequently becomes infected, and the inflamed bladder (cystitis)
adds to the patient’s symptoms.
In all operations on the prostate, the surgeon regards the prostatic
venous plexus with respect. The veins have thin walls, are valveless, and are
drained by several large trunks directly into the internal iliac veins. Damage
to these veins can result in a severe hemorrhage.
Prostate
Cancer and the Prostatic Venous Plexus
Many connections between the prostatic venous plexus and the
vertebral veins exist. During coughing and sneezing or abdominal straining, it
is possible for prostatic venous blood to flow in a reverse direction and enter
the vertebral veins. This explains the frequent occurrence of skeletal
metastases in the lower vertebral column and pelvic bones of patients with
carcinoma of the prostate. Cancer cells enter the skull via this route by
floating up the valveless prostatic and vertebral veins
