Urinary System Anatomy Overview

Urinary System Anatomy Overview

• The urinary system maintains normal blood and tissue fluid composition, volume, and pH by removing substances that disrupt balance.
• It regulates blood volume by filtering and conserving water and other substances.
• Electrolyte balance is regulated via excretion or conservation of minerals.
• Acid-base balance relies on excretion or conservation of ions like H+ and HCO₃⁻.

Urinary System Organs

• Kidneys (2): Paired organs located in the posterior body wall, retroperitoneal.
• Ureters (2): Carry urine from kidneys to the bladder.
• Urinary Bladder: Stores urine.
• Urethra: Transports urine from the bladder to the outside of the body.

Kidney Location and Protection

• Kidneys are retroperitoneal, meaning located behind the peritoneum.
• They are protected by layers of connective tissue:
  • Renal capsule: A fibrous covering providing protection and maintaining kidney shape.
  • Adipose capsule (perirenal fat): Cushions and stabilizes the kidneys.
  • Renal fascia: Holds the kidneys in place, in contact with the muscles of the posterior abdominal wall.

Kidney Structure

• Renal cortex: Outer layer containing nephrons.
• Renal medulla: Inner layer containing renal pyramids with nephrons.
• Renal pelvis: A funnel-shaped structure collecting urine and connecting to the ureters.

Nephron

• Functional units: Microscopic filtering structures within the kidney.
• Two parts:
  • Renal corpuscle: Globe-shaped structure with filtering capillaries (glomerulus).
  • Renal tubule: Long, tubular structure reabsorbing needed components.

Urine Formation and Flow

• Urine drains from the minor calyx to major calyx and renal pelvis, eventually entering ureters.
• Urine is moved through the ureters and stored in the bladder by peristaltic action.
• The internal and external urethral sphincters control urine release.

Blood Supply to Kidneys

• Receiving approximately one-quarter of the total cardiac output, the kidneys receive blood via renal arteries.
• Blood is filtered through the glomerulus; then transported through the efferent arterioles to peritubular capillaries, before returning to the inferior vena cava via smaller blood vessels (interlobar, arcuate, interlobular veins).

Ureter Structure and Function

• Ureters are muscular tubes about 25-30 cm long in adults.
• The ureters carry urine from the renal pelvis to the urinary bladder.
• Peristaltic waves transport urine through the ureters.
• Bladder pressure regulates opening between ureters and bladder.

Bladder Structure and Function

• Hollow, distensible organ located in the pelvic cavity.
• The trigone is the triangular region at the base of the bladder where ureters join.
• The bladder stores urine until urination.

Urethra Structure and Function

• The final part of the urinary tract. It drains urine from the bladder to the exterior.
• Different lengths and functions in males and females:
  • Female: Shorter (4 cm), primary function: urine removal.
  • Male: Longer (20 cm), dual function in urination and ejaculation.

Male vs. Female Anatomy Differences

• Male urethra passes through prostate.
• Longer male urethra.
• Different locations in the pelvic region versus females.