Pelvic Viscera

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Urinary Bladder & Urethra - Water Works Wonders

  • Urinary Bladder: Hollow, muscular organ; retroperitoneal when empty, rises into abdomen when full.
    • Parts: Apex, body, fundus (base), neck.
    • Trigone: Smooth triangular area at base; ureteric orifices superolaterally, internal urethral orifice inferiorly.
    • Detrusor muscle: Smooth muscle of bladder wall.
    • Relations (Male): Anterior to rectum, superior to prostate.
    • Relations (Female): Anterior to uterus & vagina.
    • Arterial Supply: Superior & inferior vesical arteries (from internal iliac).
    • Innervation: Pelvic splanchnic nerves (parasympathetic - micturition), hypogastric nerves (sympathetic - storage).

Female Pelvic Viscera Sagittal View

  • Urethra:
    • Male: ~20 cm; prostatic, membranous, spongy parts. Opens at external urethral meatus.
    • Female: ~4 cm; opens into vestibule. More prone to UTIs.

⭐ The membranous urethra is the shortest, narrowest, and least dilatable part of the male urethra, passing through the urogenital diaphragm.

📌 Water Under The Bridge (Ureter passes under Vas deferens/Uterine artery).

Rectum & Anal Canal - The Grand Exit

  • Rectum: ~12-15 cm long; continuous with sigmoid colon at S3, ends at anorectal junction.
    • Sacral flexure (follows sacrum/coccyx); Anorectal flexure (80-90° angle, maintained by puborectalis sling).
    • Three transverse rectal folds (Valves of Houston).
    • Rectal ampulla: Dilated lower part, stores feces.
  • Anal Canal: ~3.8-4 cm long; from anorectal junction to anal verge.
    • Internal anal sphincter: Involuntary, smooth muscle (thickened circular layer).
    • External anal sphincter: Voluntary, skeletal muscle (subcutaneous, superficial, deep parts).
    • Pectinate (Dentate) Line: Important landmark.
      • Above: Endodermal origin, columnar epithelium, superior rectal A./V. (portal), autonomic innervation (stretch), lymph to internal iliac nodes.
      • Below: Ectodermal origin, stratified squamous epithelium, inferior rectal A./V. (systemic), somatic innervation (pain, temp, touch), lymph to superficial inguinal nodes.

⭐ The pectinate line is a critical watershed: Internal hemorrhoids (above line) are typically painless and bleed (columnar epithelium, autonomic supply), while external hemorrhoids (below line) are painful (squamous epithelium, somatic supply). Sagittal view of rectum and anal canal anatomy

Male Internal Genitalia - Procreation Powerhouse

Sagittal view of male pelvic viscera

  • Vas Deferens (Ductus Deferens):
    • Muscular tube; transports sperm from epididymis to ejaculatory duct.
    • Component of the spermatic cord.
  • Seminal Vesicles:
    • Paired glands posterior to bladder, superior to prostate.
    • Produce alkaline, fructose-rich fluid (major part of semen volume, ~70%).
    • Ducts join vas deferens to form ejaculatory ducts.
  • Ejaculatory Ducts:
    • Formed by union of vas deferens ampulla & seminal vesicle duct.
    • Traverse prostate; open into prostatic urethra.
  • Prostate Gland:
    • Surrounds prostatic urethra at bladder neck.
    • Contributes ~25% to seminal fluid (thin, milky, slightly acidic; contains PSA).
    • Zones:
      • Peripheral Zone (PZ): Largest (~70%); common site of carcinoma.
      • Central Zone (CZ): Surrounds ejaculatory ducts.
      • Transitional Zone (TZ): Surrounds urethra; site of Benign Prostatic Hyperplasia (BPH).

⭐ The Peripheral Zone (PZ) of the prostate is the most frequent site of prostatic adenocarcinoma, while the Transitional Zone (TZ) is typically involved in Benign Prostatic Hyperplasia (BPH).

Female Internal Genitalia - Creation Central

  • Ovaries: Paired, produce ova & hormones.
    • Ligaments: Suspensory (contains ovarian vessels), Ovarian (connects ovary to uterus).
    • Arterial Supply: Ovarian artery (from abdominal aorta).
    • Venous Drainage: Ovarian vein (Right to IVC, Left to Left renal vein).
  • Uterine Tubes (Fallopian): Conduct ova from ovary to uterus.
    • Parts: Infundibulum (with fimbriae), Ampulla, Isthmus, Intramural part.
  • Uterus: Pear-shaped, muscular organ for gestation.
    • Parts: Fundus, Body, Cervix. Position: Usually anteverted & anteflexed.
    • Supports: Broad ligament, Round ligament, Cardinal (transverse cervical/Mackenrodt's) ligament, Uterosacral ligaments.
    • Arterial Supply: Uterine artery (branch of internal iliac artery). 📌 Mnemonic: "Water (ureter) under the bridge (uterine artery)".
  • Vagina: Fibromuscular tube extending from cervix to vestibule.
    • Fornices: Anterior, posterior (deepest), and lateral recesses around cervix.

Sagittal view of female pelvic viscera

⭐ The ampulla of the uterine tube is the most common site of fertilization and also the most common site for ectopic pregnancies.

High‑Yield Points - ⚡ Biggest Takeaways

  • Rectum: Features Houston's valves (transverse folds) and the Pectinate line.
  • Urinary Bladder: Trigone is smooth, fixed; Detrusor muscle forms its wall.
  • Ureters: Enter bladder posteroinferiorly; Uterine artery/Vas deferens crosses superiorly ("water under the bridge").
  • Prostate: Peripheral zone for carcinoma; Transitional zone for BPH.
  • Uterus: Normally anteverted and anteflexed; Broad ligament is key support.
  • Pelvic Blood Supply: Mainly from Internal Iliac Artery branches.

Practice Questions: Pelvic Viscera

Test your understanding with these related questions

Which of the following is not felt with a digital rectal examination?

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Flashcards: Pelvic Viscera

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The _____ zone of the prostate primarily surrounds the ejaculatory ducts.

TAP TO REVEAL ANSWER

The _____ zone of the prostate primarily surrounds the ejaculatory ducts.

central

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