Male Pelvic Organs

Base:

• Superior surface, in direct continuity with the bladder neck, receiving the preprostatic urethra as it enters.

Apex:

• Inferior extremity, resting on the pelvic floor (urogenital diaphragm/deep perineal pouch), continuous with the membranous urethra below it.

Surfaces:

• Anterior (related to the pubic symphysis, separated by the retropubic space and puboprostatic ligaments), posterior (related to the rectum, separated by Denonvilliers' fascia (rectovesical septum): a key surgical dissection plane), and two inferolateral surfaces (related to levator ani and the prostatic venous plexus/neurovascular bundles).

Lobes (traditional anatomical description):

• Anterior, posterior, median (middle), and two lateral lobes: a classical descriptive scheme, of limited direct clinical/surgical relevance today, largely superseded by zonal anatomy.

Zonal anatomy (McNeal's zones: the clinically dominant classification):

• Peripheral zone: The largest zone (~70% of glandular volume), posterior and posterolateral, palpable on digital rectal examination, the site of origin of the majority of prostate cancers (~70-80%).
• Central zone: Surrounds the ejaculatory ducts, cone-shaped, relatively resistant to both cancer and benign hyperplasia.
• Transition zone: Surrounds the preprostatic urethra, small in young men but the site of benign prostatic hyperplasia (BPH) growth, which can enlarge substantially with age, compressing the urethra and accounting for the classic lower urinary tract symptoms of BPH.
• Anterior fibromuscular stroma: Non-glandular tissue, forms the anterior surface, of minimal clinical significance for pathology but contributes to the gland's overall structural support.

Capsule:

• A thin fibromuscular capsule surrounds the gland, though it is incomplete/discontinuous in places (particularly posterolaterally, where the neurovascular bundles perforate it), relevant to the assessment of extracapsular extension in prostate cancer staging.

Relations:

• Anterior: Pubic symphysis, retropubic space, puboprostatic ligaments.
• Posterior: Rectum (separated by Denonvilliers' fascia), this relationship is the anatomical basis for digital rectal examination (DRE) of the prostate, palpating the peripheral zone directly through the rectal wall.
• Superior: Bladder base/neck.
• Inferior: Deep perineal pouch/urogenital diaphragm (apex rests here).
• Lateral: Levator ani, and the neurovascular bundles (posterolateral, within the fascial layers just outside the capsule, critical structures for nerve-sparing prostatectomy).

Prostatic urethra:

• Traverses the gland from base to apex, the widest part of the male urethra, with the posterior wall marked by the urethral crest and seminal colliculus (verumontanum): the site of the ejaculatory duct openings and the prostatic utricle (a small blind-ending pouch, the vestigial remnant of the fused paramesonephric ducts, functionally the male homologue of the uterus/upper vagina).

Ejaculatory ducts:

• Formed by the union of the ductus deferens and the seminal vesicle duct, traversing the prostate to open on the seminal colliculus within the prostatic urethra.

Blood supply:

• Inferior vesical artery (predominant supply) and middle rectal artery (smaller contribution), both branches of the internal iliac artery's anterior division.

Venous drainage:

• Prostatic venous plexus, draining to the internal iliac vein and (critically) communicating with the internal vertebral venous plexus (Batson's plexus), the valveless pathway explaining prostate cancer's characteristic pattern of vertebral/axial skeletal metastasis.

Lymphatics:

• Predominantly to the internal iliac and obturator nodes, with some drainage to the external iliac and sacral nodes, relevant to the surgical/oncological template for pelvic lymph node dissection in prostate cancer staging.

Innervation:

• Autonomic (sympathetic and parasympathetic) via the inferior hypogastric plexus, with the relevant nerve fibres running within the neurovascular bundles at the posterolateral aspect of the gland, the anatomical target of nerve-sparing radical prostatectomy technique, aiming to preserve erectile and continence function by avoiding these bundles during gland removal.

Position:

• Paired, elongated, coiled glandular structures lying posterior to the bladder base, superior to the prostate, lateral to the ampullae of the ductus deferens.

Relations:

• Posteriorly related to the rectum (separated by Denonvilliers' fascia, the same plane relevant to the prostate's posterior relation), palpable on DRE in some individuals, particularly if enlarged/inflamed.

Ducts:

• Each seminal vesicle's duct joins the corresponding ductus deferens ampulla to form the ejaculatory duct.

Blood supply:

• Branches of the inferior vesical and middle rectal arteries, mirroring the prostate's supply given the shared anatomical region.

Function (contextual note, brief):

• Contribute the majority of the volume of seminal fluid (fructose-rich secretions supporting sperm viability/motility), though detailed physiology is outside the scope of this anatomical content.

Pelvic course:

• Continues from the spermatic cord (see Abdomen content, Inguinal Region) after passing through the deep inguinal ring, crossing over the external iliac vessels to enter the pelvis, then running medially and posteriorly along the lateral pelvic wall, crossing superior to the ureter near the bladder base (a notable, distinct crossing relationship from the uterine artery-ureter relationship in females, here it is the ductus deferens crossing over the ureter, sometimes remembered as analogous in principle though anatomically and clinically distinct) before reaching the posterior bladder base.

Ampulla:

• The dilated terminal portion of the ductus deferens, just before it joins the seminal vesicle duct to form the ejaculatory duct, a storage reservoir for spermatozoa.

Relation to ureter:

• The ductus deferens crosses anterior to and superior to the ureter as both structures approach the bladder base (the ureter continuing more posteriorly/inferiorly to reach the bladder wall, the ductus deferens curving medially toward the seminal vesicle/prostate base), a relationship of surgical relevance during pelvic procedures in males (e.g., radical prostatectomy, pelvic lymph node dissection), analogous in surgical importance (though anatomically distinct in specifics) to the uterine artery-ureter relationship that dominates female pelvic surgical anatomy.

• Formed by the union of the ductus deferens (ampulla) and the seminal vesicle duct, a short paired structure (~2 cm) passing through the substance of the prostate to open on the seminal colliculus within the prostatic urethra, flanking the prostatic utricle.
• Given their course through the prostate, ejaculatory duct obstruction can occur secondary to prostatic pathology (cysts, calculi, inflammation), contributing to a subset of male infertility cases.

• The ureter crosses the pelvic brim near the bifurcation of the common iliac artery, descends along the lateral pelvic wall (anterior to the internal iliac artery's origin), then curves medially and anteriorly to reach the bladder base, passing posterior to (deep to) the ductus deferens just before entering the bladder wall, this specific ordering (ductus deferens crossing anterior/superior to the ureter) is the male-specific equivalent of the uterine artery-ureter relationship that receives greater emphasis in female pelvic anatomy, but remains clinically relevant to avoiding ureteric injury during male pelvic surgery.

• The rectum lies immediately posterior to the bladder, seminal vesicles, and prostate throughout the male pelvis, separated from these structures by Denonvilliers' fascia (rectovesical/rectoprostatic septum): this consistent posterior relationship underlies both the diagnostic utility of digital rectal examination (palpating the prostate and, when enlarged, the seminal vesicles) and the surgical dissection planes used in radical prostatectomy and rectal cancer surgery, where Denonvilliers' fascia serves as the key anatomical plane of separation.

• The cavernous nerves (parasympathetic fibres from the pelvic splanchnic nerves, via the inferior hypogastric plexus, mediating erection) run within the neurovascular bundles at the posterolateral aspect of the prostate, closely applied to (but just outside) the prostatic capsule, running alongside small branches of the inferior vesical/prostatic vessels.
• Nerve-sparing radical prostatectomy technique is built entirely around preserving these bundles by carefully dissecting along the prostatic capsule rather than more widely, balancing the oncological need for adequate cancer clearance against the functional goal of preserving erectile function, the single most anatomically-driven technical consideration in modern prostate cancer surgery.

Benign prostatic hyperplasia (BPH):

• Arises specifically from the transition zone, surrounding the preprostatic urethra, as this zone enlarges with age, it compresses/distorts the urethra, producing the classic lower urinary tract symptoms (hesitancy, weak stream, incomplete emptying, frequency, nocturia).
• Distinct anatomically and zonally from prostate cancer, which arises predominantly from the peripheral zone, explaining why BPH and prostate cancer can coexist without one necessarily causing or worsening the other, despite both being common age-related prostatic conditions.

Prostate cancer spread:

• Local spread from the peripheral zone can extend posteriorly toward the rectum (limited by Denonvilliers' fascia, though advanced disease can breach it), laterally toward the neurovascular bundles (relevant to nerve-sparing surgery decision-making, bundles may need to be sacrificed if cancer has extended toward them), and superiorly toward the seminal vesicles/bladder base.
• Lymphatic spread follows the internal iliac/obturator node pathway; haematogenous spread follows the prostatic venous plexus → Batson's plexus route, explaining the characteristic pattern of vertebral and pelvic bone metastasis, often occurring even before more typical haematogenous spread to lungs/liver via the systemic venous system.

Urinary obstruction:

• Most commonly caused by BPH (transition zone enlargement compressing the prostatic urethra) in older men; can also result from prostate cancer (peripheral zone disease extending to compress the urethra in advanced cases, though this is a less common presentation than BPH-related obstruction), urethral stricture (often at the vulnerable membranous urethra, post-traumatic or post-instrumentation), or bladder neck dysfunction.