Urinary Bladder Anatomy: Midline Location, Relations, and Clinical Relevance

The urinary bladder is a midline, distensible muscular organ in the lesser pelvis.

Location & Relations

• Position: Posterior to pubic symphysis, anterior to rectum (male) or uterus/vagina (female).
• Peritoneal reflection: Dome covered by peritoneum; rest extraperitoneal.
• Supports: Puboprostatic ligaments (M), pubovesical ligaments (F), levator ani, endopelvic fascia.

Internal Anatomy

• Trigone: Triangular area between ureteric orifices and internal urethral orifice; mucosa smooth, fixed, sensitive.
• Detrusor muscle: Smooth muscle (longitudinal/circular/longitudinal) – contracts for voiding.
• Internal urethral sphincter: Involuntary (sympathetic, α1).
• External urethral sphincter: Skeletal muscle (somatic, pudendal nerve) – voluntary continence.

Vascular/Nerve Supply

• Arteries: Superior/inferior vesical (from internal iliac).
• Nerves: Pelvic plexus (parasympathetic S2–S4 → contraction; sympathetic T11–L2 → relaxation/filling).

Clinical Correlates

• Suprapubic aspiration/catheterization: midline, 2 cm above pubis.
• Bladder outlet obstruction (BPH, stricture) → trabeculation, diverticula.
• Neurogenic bladder: upper motor neuron (spastic) vs. lower motor neuron (flaccid).