SN1 SHORT NOTE 5M ★ High-yield

Describe the prostate with its lobes, zones, relations and applied anatomy.

Anatomy · 1st Professional — Pre-Clinical

The prostate is a fibromuscular glandular organ surrounding the prostatic urethra, lying below the neck of the bladder.

Size of a chestnut — about 4 3 2 cm, weighing 8–20 g in the young adult
Has a base above (fused with the bladder neck), an apex below resting on the urogenital diaphragm, and anterior, posterior and inferolateral surfaces
Enclosed in a true capsule, and outside it a false capsule derived from pelvic fascia, containing the prostatic venous plexus

Traditional lobe	Position	Clinical relevance
Anterior (isthmus)	In front of the urethra	Fibromuscular; no glands
Median	Between the urethra and the ejaculatory ducts	Enlarges in benign hypertrophy → obstructs the internal urethral orifice
Posterior	Behind the ejaculatory ducts	The usual site of carcinoma; palpable on rectal examination
Right and left lateral	On either side	Also enlarge in hypertrophy

McNeal zone	Share of gland	Disease
Transitional zone	5–10%	Benign prostatic hyperplasia
Central zone	25%	Rarely diseased
Peripheral zone	70%	Carcinoma (about 70–80%)

Anterior — retropubic space, pubic symphysis, prostatic venous plexus
Posterior — rectum, separated by the fascia of Denonvilliers; hence palpable per rectum
Superior — bladder neck; inferior — urogenital diaphragm
Lateral — levator ani (levator prostatae)

Arteries — inferior vesical, middle rectal and internal pudendal, all from the internal iliac
Veins — the prostatic venous plexus drains into the internal iliac vein, and communicates with the vertebral venous plexus of Batson
Nerves — from the inferior hypogastric plexus; the cavernous nerves run in the neurovascular bundles posterolaterally and must be spared in radical prostatectomy to preserve erectile function

Benign prostatic hyperplasia — causes hesitancy, poor stream, terminal dribbling, frequency and nocturia, and eventually retention, hydronephrosis and renal failure
Carcinoma of the prostate metastasises to the vertebrae through the valveless vertebral venous plexus, bypassing the lungs; the deposits are characteristically osteoSCLEROTIC, unlike most other secondaries
Digital rectal examination — a hard, irregular, nodular gland with loss of the median sulcus suggests carcinoma; a smooth, firm, enlarged gland suggests benign hyperplasia
Prostate specific antigen is raised in carcinoma but also in benign hyperplasia, prostatitis, and after rectal examination or catheterisation — so it is not diagnostic alone
Transurethral resection (TURP) removes the obstructing transitional zone through the urethra; it causes retrograde ejaculation because the bladder neck is destroyed

All questions in Pelvis & Perineum