Bladder / Urethra Anatomy

Introduction

• The urinary organs consist of
  • ureters (pelvic portion)
    • carries urine from the kidney into the bladder
  • urinary bladder
    • the site of temporary urine storage
  • urethra
• the conduction site of urine from the urinary bladder to the external world

Ureters

• Muscular tubes that carries urine from the kidney into the bladder
  • they are retroperitoneal structures that pass beneath the
    • uterine artery (in females)
      • clinical correlate
        • uterine or ovarian vessel ligation in gynecologic procedures may damage the ureter 
    • vas deferens (in males)
• Blood supply consists of branches from 
  • renal arteries (most proximal)
  • testicular arteries (in men) and ovarian arteries (in women)
  • the descending aorta 
  • internal iliac arteries
  • superior vesical arteries
  • uterine arteries (in women) 
• vaginal arteries (in women) and inferior vesical arteries (in men) (most distal)

Urinary Bladder

• A temporary reservoir of urine
• Innervation
  • parasympathetic fibers
    • conveyed from the sacral spinal cord via the pelvic splanchnic nerves and inferior hypogastric plexus
    • provide motor innervation to the detrusor muscle
    • inhibits contraction of the internal urethral sphincter in men
  • sympathetic fibers
    • conveyed from the lower thoracic and upper lumbar spinal cord via the hypogastric plexus and nerves
• promotes contraction of the internal urethral sphincter

Urethra

• A muscular tube that allows urine to travel from the urinary bladder to the external world
  • the urethra also provides an exit path for semen
  • the female urethra is much shorter (~4 cm) than the male urethra (~18-22 cm)
    • this is a reason as to why women are more prone to developing urinary tract infections than men 
• Urethral injury
  • posterior urethra
    • the weakest point is in the bulbomembranous junction
    • prone to injury in pelvic fractures (e.g., from a motor vehicle accident)
      • can result in urine or blood being found in the retropubic space
  • anterior urethra
    • injury to the anterior urethra can result from
      • straddle injuries
      • instrumentation
      • pelvic fracture (in conjunction)
      • direct blow
    • injury can result in urine or blood being found in the
      • deep fascia of Buck
      • superficial perineal space
        • when the deep fascia of Buck is torn