Urology>>>>>Anatomy & Embryology
Question 8#

Which of the following is TRUE regarding the prostate?

A. The prostate gland develops from the distal nephric ducts
B. The majority of cancers originate from the central zone
C. Fibromuscular stroma makes up 70% of the prostate
D. The blood supply to the prostate is from the pudendal artery
E. The glandular elements drain into the urethra at the verumontanum

Correct Answer is E

Comment:

Answer E

The prostate develops during the 10th–12th week of gestation under influence of testosterone. The urogenital sinus gives off a prostatic bud comprised of solid epithelial cords, which canalise into solid prostatic ducts, and the epithelial cells become luminal and basal cells. The prostatic mesenchyme differentiates into smooth muscle cells to surround the ducts. There is a marked increase in the size of the prostate at puberty under the influence of testosterone and secretion of prostate specific antigen occurs. The gland is ovoid in shape, lies at the base of the bladder and weighs roughly 18 g in the normal adult. A fibrous capsule surrounds the gland composed of predominant glandular tissue (70%) and fibromuscular stroma (30%). It has an anterior, posterior and lateral surface with an inferior apex that lies on the urogenital diaphragm and a superior base. The prostate is further anatomically divided the gland into four zones based on the glandular elements.

1. Peripheral – Located posterior-laterally and forms the bulk of the gland. The ducts drain into the prostatic sinus. 75% of cancers arise from this zone.
2. Central – Cone-shaped zone that extends from around ejaculatory ducts to the base of the bladder. 
3. Transitional – Surrounds the urethra and is separated from the other zones by a thin band of fibromuscular tissue. More commonly gives rise to benign prostatic hyperplasia.
4. Anterior fibromuscular stroma – Non-glandular segment extending from the bladder neck to the external urethral sphincter. 

The rectum is posterior to the gland, separated by Denonvilliers’ fascia and a loose layer of areolar tissue, the endopelvic fascia anterolaterally and the pubococcygeal muscles of levator ani laterally. Near the apex, the puboprostatic ligaments are on either side of the midline that extend from the prostate to the pubic bone. The base is continuous with the bladder neck where the detrusor muscle fibres merge with the capsule. The prostatic urethra is about 3 cm long and runs through the prostate from the bladder neck to become the membranous urethra. On the posterior wall, is a longitudinal ridge (urethral crest) that runs the length of the gland in between two grooves (prostatic sinus) into which the glandular elements open into the urethra. The crest widens distally to form the verumontanum. At its apex lies the slit-like prostatic utricle and represents a Müllerian remnant. The ejaculatory ducts open on either side of this. The main blood supply to the prostate is from the inferior vesical artery, which becomes the prostatic artery and divides into two main branches. The urethral arteries enter the prostate at the junction with the bladder and approach the bladder neck at the 1–11 (Flock) and 5–7 (Badenoch) o’clock positions. From here they run parallel to the urethra to supply the transition zone and periurethral glands. The capsular arteries supply the capsule and glandular tissues. The veins of the prostate drain into the dorsal vein complex lying just beneath the pubic symphysis; the deep dorsal vein leaves the penis under Buck’s fascia and penetrates the urogenital diaphragm dividing into three major branches – the superficial branch and the right and left lateral plexus. The superficial branch pierces the endopelvic fascia and runs over the neck and anterior bladder surface to drain the anterior prostate, bladder and retropubic fat. The lateral branches pass down the sides of the prostate to join the vesical plexus, which subsequently drains into the internal iliac veins.