Anatomy Overview: The Urinary System

Overview

• Primary Components: Kidneys (right and left), ureters, urinary bladder, urethra.
• Location:
  • Kidneys: Upper abdomen.
  • Ureters: Connect each kidney to the bladder.
  • Bladder: Medial pelvic region.
  • Urethra: Connects bladder to the outside of the body.
• Functions:
  • Homeostasis of body fluids.
  • Alters blood composition.
  • Forms urine.
  • Regulates body fluid pH.

Kidney

• Images: Anterior view, cross-section, and photo of a cross-section.
• Parts Labeled:
  • Ureter, renal artery, renal vein, renal capsule.
  • Nephron, renal cortex, renal medulla.
  • Urine flow sequence: Collecting duct → Papillary duct → Renal calyx → Renal pelvis → Ureter.
• Structure:
  • Multiple renal lobes separated by renal columns.
  • Nephron starts in cortex, dips into medulla, returns to cortex.
• Functions:
  • Regulates blood levels of water-soluble substances (e.g., sodium, potassium, calcium).
  • Regulates blood volume and pressure by conserving or eliminating water.
  • Regulates body fluids pH.
  • Releases hormones: Erythropoietin (increases hematocrit) and Calcitriol (decreases blood calcium).
  • Releases enzyme Renin for producing Angiotensin II.

Ureters, Urinary Bladder, and Urethra

• Images: Anterior view of the frontal section and micrograph of ureter.
• Parts Labeled:
  • Internal and external urethral sphincters, ureters, urinary bladder, lumen, muscularis layer (detrusor muscle), mucosal layer (transitional epithelium), peritoneum, adventitia.
  • Ureters connect superiorly to the bladder; bladder held in place by peritoneum.
  • Urethra connects bladder to outside of body.
• Functions:
  • Ureters transport urine to the bladder.
  • Urinary bladder stores and ejects urine.
  • Urethra discharges urine from the body.

Blood Supply of the Kidneys

• Images: Nephron structure, cross-section of kidney, and blood flow path.
• Blood Flow Path:
  • Renal artery → Segmental arteries → Interlobar arteries → Arcuate arteries → Interlobular arteries → Afferent arterioles → Glomerular capillaries → Efferent arterioles → Peritubular capillaries/Vasa recta → Interlobular veins → Arcuate veins → Interlobar veins → Segmental veins → Renal vein.
• Functions:
  • Strong blood flow allows kidneys to remove wastes.
  • Regulates volume and ionic composition of body fluid.