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The Urinary System

PART 3. The Urinary System. Microscopic Anatomy of the Kidney. Juxtaglomerular apparatus Functions in the regulation of blood pressure Juxtaglomerular cells – secrete renin Macula densa A portion of distal convoluted tubule Tall, closely packed epithelial cells Act as chemoreceptors.

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The Urinary System

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  1. PART 3 The Urinary System

  2. Microscopic Anatomy of the Kidney • Juxtaglomerular apparatus • Functions in the regulation of blood pressure • Juxtaglomerular cells – secrete renin • Macula densa • A portion of distal convoluted tubule • Tall, closely packed epithelial cells • Act as chemoreceptors

  3. Juxtaglomerular Apparatus Figure 23.10

  4. Ureters • Carry urine from the kidneys to the urinary bladder • Oblique entry into bladder prevents backflow of urine • Histology of ureter • Mucosa – transitional epithelium • Muscularis – two layers • Inner longitudinal layer • Outer circular layer • Adventitia – typical connective tissue

  5. Microscopic Structure of the Ureter Figure 23.12

  6. Urinary Bladder • A collapsible muscular sac • Stores and expels urine • Full bladder – spherical • Expands into the abdominal cavity • Empty bladder – lies entirely within the pelvis Figure 23.13

  7. Urinary Bladder • Urachus – closed remnant of the allantois • Prostate gland • In males • Lies directly inferior to the bladder • Surrounds the urethra Figure 23.14

  8. Urinary Bladder • Wall of bladder • Mucosa • Transitional epithelium • Muscular layer • Detrus or muscle • Adventitia

  9. Histology of the Urinary Bladder Figure 23.15a, b

  10. Structure of the Urinary Bladder and Urethra Figure 23.16a

  11. Structure of the Urinary Bladder and Urethra Figure 23.16b

  12. Urethra • Epithelium of urethra • Transitional epithelium • At the proximal end (near the bladder) • Stratified and pseudostratified columnar – mid urethra (in males) • Stratified squamous epithelium • At the distal end (near the urethral opening)

  13. Urethra • Internal urethral sphincter • Involuntary smooth muscle • External urethral sphincter • Voluntarily inhibits urination • Relaxes when one urinates

  14. Urethra • In females • Length of 3–4 cm • In males – 20 cm in length – three named regions • Prostatic urethra • Passes through the prostate gland • Membranous urethra • Through the urogenital diaphragm • Spongy (penile) urethra • Passes through the length of the penis

  15. Micturition Figure 23.17

  16. Disorders of the Urinary System • Urinary tract infections • More common in females • Burning sensation during micturition • Renal calculi • Kidney stones • Bladder cancer • 3% of cancers – more common in men • Kidney cancer • Arises from epithelial cells of uriniferous tubules

  17. The Urinary System Throughout Life • Embryo develops three pairs of kidneys • Pronephros • Mesonephros • Metanephros • Only metanephros persists to become the adult kidneys • Metanephric kidney produces urine by fetal month three • Contributes to the volume of amniotic fluid

  18. Development of the Urinary Organs Figure 23.18a,b

  19. Development of the Urinary Organs Figure 23.18c, d

  20. The Urinary System Throughout Life • Kidney and bladder function declines with advancing age • Nephrons decrease in size and number • Tubules less efficient at secretion and reabsorption • Filtration declines • Recognition of desire to urinate is delayed • Loss of muscle tone in the bladder

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