Reproductive Anatomy, Drainage & Sexual Response

Female pelvic ligaments and the ureter

What each ligament carries. The uterus, tubes and ovaries hang in the pelvis from peritoneal folds and condensed connective tissue. Knowing which vessel runs in which ligament explains adnexal torsion, surgical bleeding and ureteral injury.

Suspensory ligament. Also called the infundibulopelvic ligament, it carries the ovarian artery (a direct branch of the abdominal aorta just below the renal arteries), the ovarian vein, lymphatics and nerves from the lateral pelvic wall to the ovary. In adnexal torsion the ovary rotates on this pedicle, obstructing venous and lymphatic outflow first and then arterial inflow. It is clamped during oophorectomy.

Cardinal ligament and the ureter. The cardinal (transverse cervical, Mackenrodt) ligament anchors the cervix and upper vagina to the pelvic wall and carries the uterine artery and vein; together with the uterosacral ligaments it is the main passive support against uterine prolapse. About 2 cm lateral to the cervix, at the base of the broad ligament, the ureter passes beneath the uterine artery ("water under the bridge"). Clamping the uterine vessels during hysterectomy can therefore ligate, crush or transect the ureter, producing hydronephrosis, flank pain or a urinary fistula. A second danger point is the pelvic brim, where the ureter crosses the iliac vessels right beside the infundibulopelvic ligament. In men the vas deferens crosses over the ureter in the same way near the bladder.

Round and ovarian ligaments. Both are remnants of the gubernaculum. The ovarian ligament ties the ovary to the uterine cornu. The round ligament runs from the cornu through the deep inguinal ring and inguinal canal to the labia majora, helps keep the uterus anteverted, carries a small artery (the artery of Sampson) and stretches painfully as the uterus enlarges in pregnancy. A patent peritoneal sleeve alongside it, the canal of Nuck, is the female equivalent of the processus vaginalis and the site of female inguinal hernia or hydrocele.

Broad ligament. A double fold of peritoneum draped over the uterus, tubes and ovaries and extending to the pelvic side wall. Its parts are the mesosalpinx around the tube, the mesovarium suspending the ovary and the mesometrium, the largest part, beside the uterus. The round and ovarian ligaments run within it, and the uterine vessels cross its base above the ureter.

Venous and lymphatic drainage

Gonadal veins. The right gonadal vein drains obliquely into the IVC, while the left drains into the left renal vein at a right angle, a longer column under higher pressure. Most varicoceles are therefore left-sided. A new left varicocele can signal a left renal cell carcinoma extending into the renal vein, or nutcracker compression of the left renal vein between the aorta and superior mesenteric artery. A varicocele that does not empty when the patient lies supine, or an isolated right-sided one, suggests obstruction by a retroperitoneal mass and warrants abdominal imaging.

Lymph follows embryology. The gonads develop in the upper lumbar retroperitoneum and descend, trailing their vessels and lymphatics, so ovarian and testicular lymph drains to the para-aortic nodes near the renal hila. Structures derived from skin drain to the groin.

Scrotal skin drains to superficial inguinal nodes but the testis drains to para-aortic nodes, so a testicular mass is removed by inguinal orchiectomy; a trans-scrotal approach risks opening a new lymphatic route to the groin.

Epithelial lining of the female tract

• Vulvar skin: keratinized stratified squamous epithelium with hair follicles and glands.
• Vagina and ectocervix: nonkeratinized stratified squamous epithelium. The vagina has no glands; estrogen fills its cells with glycogen, which lactobacilli ferment to lactic acid, holding pH around 3.8–4.5. After menopause the epithelium thins and pH rises.
• Endocervix: simple columnar mucus-secreting epithelium lining branching crypts.
• Endometrium: simple columnar epithelium with tubular glands, straight in the proliferative phase and coiled in the secretory phase.
• Fallopian tube: simple columnar epithelium with ciliated cells and secretory (peg) cells; ciliary beating moves the ovum toward the uterus, so scarring or ciliary dyskinesia causes infertility and ectopic pregnancy.
• Ovarian surface: simple cuboidal epithelium, historically misnamed the germinal epithelium.

Transformation zone. Where the endocervical columnar epithelium meets the ectocervical squamous epithelium, columnar cells are gradually replaced by squamous cells (squamous metaplasia). This metaplastic zone is the cells' most vulnerable state for infection by high-risk HPV (types 16 and 18), so cervical intraepithelial neoplasia and squamous cell carcinoma arise here and cervical screening must sample it. The junction moves outward onto the ectocervix (ectropion) when estrogen is high, as at puberty, in pregnancy and with combined oral contraceptives, and recedes into the canal after menopause. Metaplastic epithelium that covers endocervical gland openings traps mucus, forming benign nabothian cysts.

Male reproductive tract

Route of sperm. Sperm made in the testis must travel a long duct system before ejaculation.

Accessory glands. The seminal vesicles supply most of the semen volume, including fructose for sperm energy and prostaglandins; the prostate adds PSA, which liquefies the coagulum, plus zinc and citrate; the bulbourethral (Cowper) glands release lubricating mucus before ejaculation.

Sexual response and its disorders

Erection. Parasympathetic fibers from the pelvic splanchnic nerves and the vascular endothelium release nitric oxide, which activates guanylyl cyclase and raises cGMP. Cavernosal arteriolar and trabecular smooth muscle relaxes, the sinusoids fill with blood and compress the subtunical venules against the tunica albuginea, trapping blood (veno-occlusion). PDE5 inhibitors such as sildenafil and tadalafil block cGMP breakdown and potentiate this pathway.

PDE5 inhibitors must not be combined with nitrates: both raise cGMP in vascular smooth muscle, and the combination can cause profound hypotension.

Emission and ejaculation. During emission, sympathetic fibers in the hypogastric nerves contract the vas deferens, seminal vesicles and prostate, depositing semen in the prostatic urethra, while α1-mediated contraction of the internal urethral sphincter seals the bladder neck. Ejaculation proper is somatic: the pudendal nerve drives rhythmic contractions of the bulbospongiosus and ischiocavernosus that propel semen out.

Retrograde ejaculation. If the bladder neck fails to close, semen passes backward into the bladder: orgasm with little or no ejaculate, and cloudy post-orgasm urine containing sperm. Causes include diabetic autonomic neuropathy, transurethral resection of the prostate or prostatectomy, retroperitoneal lymph node dissection (sympathetic injury), spinal cord injury and α1-blockers such as tamsulosin.

Erectile dysfunction. Organic ED is most often vascular: atherosclerosis from smoking, diabetes, hypertension and dyslipidemia, or aortoiliac occlusion in Leriche syndrome (buttock and thigh claudication, weak femoral pulses, ED). Because penile arteries are small, ED can precede symptomatic coronary disease by years. Neurogenic causes include diabetic neuropathy, spinal cord injury, multiple sclerosis and injury to the cavernous nerves, which run posterolateral to the prostate, during radical prostatectomy. Hormonal causes (low testosterone, hyperprolactinemia) usually reduce libido as well. Drug causes include β-blockers, thiazides, SSRIs, antipsychotics (partly via raised prolactin) and 5α-reductase inhibitors.

Psychogenic ED. Onset is abrupt and situational, for example with one partner, often with performance anxiety or depression. Nocturnal and morning erections persist because nerves and vessels are intact; loss of nocturnal penile tumescence points to an organic cause.