Anatomy of the Urinary System

Overview

• The urinary system consists of kidneys, ureters, urinary bladder, and urethra.
• This lecture focuses on the ureter, urinary bladder, and urethra in both males and females.

Ureter

Function and Course

• Transports urine from kidneys to the urinary bladder via peristaltic movements.
• Length: ~30 cm; lies at the back of the abdominal cavity in front of the psoas major muscle.
• Differentiates crossing structures in males and females:
  • In males, crosses ductus deferens before entering the bladder.
  • In females, passes between the broad and cardinal ligaments before entering the bladder.

Structure

• Divided into three parts:
  • Abdominal part: Between renal pelvis and terminal line of the pelvis.
  • Pelvic part: Ends at the urinary bladder.
  • Intramural part: In the wall of the urinary bladder.
• Narrowings at:
  • Junction between renal pelvis and ureter.
  • Linea terminalis.
  • Wall of the urinary bladder.

Wall Layers

• Tunica mucosa (innermost): Transitional epithelium.
• Tela submucosa: Loose connective tissue with blood vessels, nerves, lymphoid tissue (in lower third).
• Tubular muscle layer:
  • Upper two-thirds: Inner longitudinal and outer circular muscles.
  • Lower third: Inner longitudinal, middle circular, outer longitudinal muscles.
• Tunica adventitia (outermost): Strong connective tissue.

Urinary Bladder

Structure

• Stores urine (capacity ~250-500 ml).
• Divided into parts:
  • Apex: Closest to the median umbilical ligament.
  • Body: Majority of the bladder.
  • Fundus: Posterior section.

Conditions

• Empty bladder: Behind the pubic symphysis, has anterior and posterior surfaces.
• Full bladder: Oval shape, rising above the pubic symphysis.

Openings

• Trigone: Triangle formed by ureteric orifices and internal urethral orifice.
• Interureteric crest: Fold between ureteric openings.

Wall Layers

• Tunica mucosa: Transitional epithelium with umbrella cells.
• Tela submucosa: Loose connective tissue, absent in the trigone.
• Tunica muscularis: Three muscle layers forming the internal urethral sphincter.
• Tunica serosa/adventitia: Serosa where in contact with peritoneum, adventitia elsewhere.

Urethra

Male Urethra

• Length: 15-22 cm, diameter: 5-7 mm.
• Parts:
  • Prostatic urethra: 3 cm, contains urethral crest, seminal colliculus.
  • Membranous urethra: 1.5-2 cm, surrounded by external urethral sphincter.
  • Spongy urethra: 15 cm, runs through penis.
• Narrowings: Internal urethral orifice, external urethral orifice, membranous urethra.
• Enlargements: Prostatic urethra, bulb of penis, navicular fossa.

Female Urethra

• Length: 2.5-4 cm, diameter: 8-12 mm.
• Structure:
  • Openings: Internal urethral orifice near bladder, external urethral orifice near clitoris.
• Wall Layers: Similar to male.
  • Tunica mucosa: Contains urethral lacuna.
  • Tunica muscularis: Forms two sphincters, internal and external.

These notes provide an overview of the anatomical features and structures of the ureter, urinary bladder, and urethra, highlighting the differences between males and females.