Embryologically, the prostate, seminal vesicles, and ductus (vas) deferens originate from 2 separate structures. The prostate arises from a budding collection of tissue in the urogenital sinus. The seminal vesicles and the ductus deferens are formed from the mesonephric duct.
The prostate develops from epithelial outgrowths form the prostatic segment of the urethra that grows into the surrounding mesenchyme. This outgrowth and branching start at week 10 during embryo growth; by week 12, there are 5 groups of tubules that form the lobes of the prostate. The first group makes up the middle lobe; the second and third groups make up the right and left lateral lobes; the fourth group is the posterior lobe that starts from the floor of the urethra; and the fifth group is the anterior lobe
A normal prostate gland is approximately 20 g in volume, 3 cm in length, 4 cm wide, and 2 cm in depth. As men get older, the prostate gland is variable in size secondary to benign prostatic hyperplasia. The gland is located posterior to the pubic symphysis, superior to the perineal membrane, inferior to the bladder, and anterior to the rectum (see the image below). The base of the prostate is in continuity with the bladder and the prostate ends at the apex before becoming the striated external urethral sphincter. The sphincter is a vertically oriented tubular sheath that surrounds the membranous urethra and prostate.
Historically, the prostate has been divided into 3 zones: (1) transition zone, (2) central zone, and (3) peripheral zone. The transition zone accounts for 10% of the prostatic glandular tissue and 20% of the adenocarcinomas. The prostate consists of approximately 70% glandular tissue and 30% fibromuscular stroma.
The prostatic urethra courses the length of the prostate from the level of the bladder neck to the level of the membranous urethra. The epithelium consists of transitional cells similar to bladder epithelium. This transitional zone is where benign prostatic hyperplasia occurs and can lead to bladder outlet obstruction when an adenoma grows to a significant size. When the adenoma grows large enough, it can compress the fibromuscular band surrounding this zone, creating a surgical capsule.
The transitional zone is often described as having 2 lateral lobes and a median lobe that lead to the symptoms of the lower urinary tract symptoms. A urethral crest runs along the posterior midline and disappears at the membranous urethra. On both sides of the urethral crest, there is a grove where the prostatic sinuses exist and drain all of the glandular elements.
The urethral crest widens and protrudes from the posterior wall as the seminal colliculus (verumontanum). A small midline pit, the prostatic utricle, is found at the apex of the seminal colliculus. On either side of the utricular orifice, the small slitlike openings to the ejaculatory duct can be found.
The arterial supply to the prostate is primarily from the inferior vesical artery, which originates from the anterior division of the internal iliac (hypogastric) artery. The inferior vesical artery then branches into 2 main arterial branches to feed the prostate. The prostatic vessels and the autonomic innervations run between the layers of the lateral prostatic fascia and the prostate. The inferior vesical artery supplies the base of the bladder, the distal ureters, and the prostate.
The first arterial branch is the urethral artery that enters the prostatovesical junction posterolaterally and travels inward perpendicular to the urethra toward the bladder neck at approximately the 5 o’clock and 7 o’clock meridian. The urethral artery then turns caudally and parallel to the urethra to supply the transition zone. This artery is the main arterial supply for the adenomas in benign prostatic hyperplasia.
The capsular artery is the second main branch of the prostate. It runs posterolateral to the prostate with the cavernous nerves. This artery enters the prostate at right angles to supply the glandular tissue.
The arterial blood supply to the seminal vessels and ductus deferens comes from the deferential artery or artery of the ductus, a branch from the superior vesical artery.
The venous drainage of the prostate starts with the deep dorsal vein, which leaves the penis under the deep penile (Buck) fascia between the corpora cavernosa and then under the pubic arch. This vein then passes anterosuperior to the perineal membrane and divides into 3 major branches, the superficial branch and the right and left branches.
The superficial branch travels between the puboprostatic ligaments and lies on top of the prostate and bladder neck. The superficial branch is outside the anterior prostatic fascia in the retropubic fat and pierces the fascia to drain into the dorsal venous complex. The common trunk of the dorsal venous complex and the lateral venous plexuses are covered by the anterior prostatic fascia and the endopelvic fascia. The lateral plexuses travel posterolaterally and communicate with the pudendal, obturator, and vesical plexus. These veins then communicate with the internal iliac vein.
The autonomic innervations of the prostate arise from the pelvic plexuses formed by the parasympathetic, visceral, efferent, and preganglionic fibers that arise from the sacral levels(S2-S4) and the sympathetic fibers from the thoracolumbar levels (L1-L2). The pelvic plexus is located beside the rectum approximately 7 cm from the anal verge, with its midpoint located at the level of the tips of the seminal vesicles.
The sympathetic and parasympathetic fibers that come from the pelvic plexuses travel to the prostate via the cavernous nerves. The cavernous nerves run posterolateral to the prostate in the lateral prostatic fascia. Two thirds of the nerve fibers run along the traditional posterolateral aspect of the prostate; however, studies of the surgical anatomy of the prostate have demonstrated that the remaining third of the nerve fibers are more anterior in the anterior lateral aspect of the prostate.  This has resulted in the “Veil of Aphrodite” technique of nerve preservation to maximize the number of nerves preserved during radical prostatectomy.  The parasympathetic nerves end at the acini and lead to prostatic secretion. The sympathetic nerves lead to contraction of the smooth muscle of the capsule and the stroma.
The pudendal nerve is the major nerve supply leading to somatic innervations of the striated sphincter and the levator ani. The preprostatic sphincter and the vesicle neck or internal sphincter is under alpha-adrenergic control.
The lymphatic drainage of the prostate primarily drains to the obturator and the internal iliac lymphatic channels. There is also lymphatic communication with the external iliac, presacral, and the para-aortic lymph nodes.