Prostate Anatomy

Prostate Anatomy, Male Reproductive Gland, Prostate Health, Human Prostate Structure

Prostate Anatomy

1. Prostate Introduction
2. Prostate External features
3. Prostate Relations
4. Prostate Lobes
5. Prostate Structural zones
6. Prostate Capsules
7. Prostate Arterial supply
8. Prostate Venous drainage and
9. Prostate Applied anatomy.

Answer:

1. Prostate Introduction:

• It is an accessory gland of the male reproductive system and adds about 30% bulk to the semen.
• It is a firm fibromuscular glandular organ surrounding the proximal part of the male urethra.
• It is located in the lesser pelvis below the neck of the urinary bladder behind the lower part of the pubic symphysis and in front of the ampulla of the rectum
• Its breadth is more than its length.

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2. Prostate External features:

It is like an inverted cone and resembles the shape of a chestnut. Its dimensions are:

• Anteroposterior = 2 cm
• Vertical = 3 cm
• Transverse = 4 cm

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The prostate presents 4 surfaces:

1. Apex: It is blunt, and the prostatic urethra emerges from its front aspect.
2. Base: It is fused with the neck of the bladder and perforated by the urethra.
3. Four surfaces:
4. Anterior: It is narrow, convex, and situated 2 cm behind the lower part of the pubic symphysis.
5. Posterior: It is broad, flat and presents a transverse groove in the upper part.
6. Right and left inferolateral surfaces: They are related to levator ani on the corresponding side.

3. Prostate Relations:

• Superiorly: The base of the prostate is fused with the neck of the urinary bladder. It is pierced by the urethra near its anterior border.
• Inferiorly: Apex of prostate blunt and rests on the urogenital diaphragm. The prostatic urethra emerges from its anterior aspect.
• Anteriorly: Anterior surface of the prostate is separated from the pubic symphysis by a retropubic space (cave of Retzius) filled with retropubic fat.
• Laterally: Inferolateral surfaces are related to that part of the levator ani, called the levator prostate.
• Posteriorly: Posterior surface is separated from the rectum by the fascia of Denonvilliers.

4. Prostate Lobes :

The prostate is divided into 5 lobes:

1. Median Or Middle lobe
2. Posterior lobe
3. Anterior lobe, and
4. Lateral (right and left) lobes.

1. Median or middle lobe:
   • It lies behind the upper part of the urethra and infront of the ejaculatory ducts. It produces a slight elevation in the lower part of the trigone of the bladder called uvula vesicae.
   • The median lobe is wedge-shaped and contains much glandular tissue; hence, it is a common site for an adenoma. The glandular tissue consists of subtrigonal glands and subcervical glands of Albarran.
   • These mucous glands are clinically important because owing to their intimate relation to the bladder neck, even a slight degree of their enlargement may lead to obstruction of urine outflow causing urinary retention.
   • The middle lobe also projects into the urethra, raising a median ridge in its floor called the urethral crest or verumontanum.
2. Posterior lobe:
   • It lies behind the middle lobe and connects the two lateral lobes.
   • It is a common site of primary carcinoma of the prostate.
3. Anterior lobe:
   • It lies in front of the urethra and does not contain glandular tissue.
   • It is, in fact, a small isthmus connecting two lateral lobes.

Right and left lateral lobes:

They lie on each side of the urethra and contain some glandular tissue; hence, the adenoma may occur rarely in these lobes in old age.

5. Prostate Structural zones:

The prostate gland presents 3 concentric zones: 

1. Peripheral zone: It is a larger zone and is situated posteriorly. It consists of long branching glands and forms 70% of the glandular tissue.
2. Central zone: It is situated posterior to the urethral lumen and above the ejaculatory ducts. It consists of a submucosal gland and constitutes 25% of the glandular tissue.
3. Periurethral zone: It is a transitional zone (5%), which along with the central zone forms the central gland. The central zone consists of mucosal (suburethral glands).

6. Prostate Capsules

Anatomically prostate is enclosed into two capsules, viz. true and false.

• True capsule:  It is a thin sheath that surrounds the gland intimately. It is formed by the condensation of peripheral fibrous stroma of the gland.
• False capsule (or prostatic sheath): It lies outside the true capsule and is derived from the visceral layer of pelvic fascia. It continues above with fascia surrounding the bladder, anteriorly with the puboprostatic ligaments, and posteriorly with the rectovesical fascia ofDenonvilliers.

The prostatic venous plexus lies between the true and false capsules.

Note:

Pathological capsule (or surgical capsule) of the prostate:

• When benign (adenomatous) hypertrophy of the prostate (BHP) takes place, the peripheral part of the gland becomes compressed to form a capsule around the adenoma termed as pathological capsule or surgical capsule.
• While performing an enucleation of the prostatic adenoma, the plane of cleavage should be between the adenomatous mass and surgical capsule so that the prostatic venous plexus lying external to the true capsule is not injured/damaged inadvertently.

7. Prostate Arterial supply

The prostate is supplied by the branches of:

• Inferior vesical artery
• Middle rectal artery
• Internal pudendal artery

8.  Prostate Venous Drainage

The veins draining the prostrate form rich venous plexus, which lies between the true and false capsules.

• Prostate Venous Drainage receives deep dorsal vein of the penis and communicates above with the vesical venous plexus to form the vesicoprostatic plexus.
• Prostate Venous Drainage drains into internal iliac veins.

9.  Prostate Applied Anatomy:

• Benign hypertrophy of the prostate (BHP): It is common after 50 years of age, hence also called senile enlargement of the prostate. It mostly occurs in the middle lobe due to hypertrophy of mucosal/periurethral glands of the central zone. Clinically, it presents as increased frequency and urgency of urination.
• Carcinoma prostate: It commonly occurs after 55 years of age mostly in the posterior lobe/outer peripheral zone of the prostate. Clinically, it presents as irregular fixed prostate with pain in perineum, urinary obstruction, and difficulty in urination.
• Prostatectomy [surgical removal/enucleation of adenoma]: The prostatic adenoma is enucleated leaving behind all the capsules. In the case if prostatic venous plexus which lies between the true and false capsules, a severed internal bleeding will occur that may be fatal.