Human Anatomy 205

• Posterior wall of abdominal cavity
• Retroperitoneal = behind the parietal peritoneum
• Hilum is indentation on medial border
• Renal adipose capsule is fatty tissue surrounding each kidney

• Renal capsule [1] (fibrous capsule) is on surface of kidney
• The outer renal cortex [contains nephron's capsule and convoluted tubules]
• Deeper renal medulla
  • Medulla contains conical renal pyramids [contains nephron loops; papillary ducts]
  • Renal papillae are at apex of renal pyramid
  • Renal columns extend between pyramids
• Central region has structures for urine collection and transport
  • renal papilla project and drain into cuplike minor calyx
  • minor calyces unite to form major calyx
  • major calyces unite to form funnel-like renal pelvis
  • renal pelvis tapers to muscular tube ureter
  • ureter trasports urine to urinary bladder

1. Glomerular (Bowman's) capsule + glomerulus [filtration]
   • See lab model Interactive glomerular capsule
   • Podocytes, in visceral epithelium of Bowman's capsule, wrap around glomerular capillaries.
   • Endothelium of glomerus with fenestrations [see illustration]
   • Noncellular basement membrane between podocytes and enothelium
   • Filtrate formed from water and solutes filtering from glomerular blood
   • Filtrate enters space of capsule
2. PCT (Proximal Convoluted Tubule) functions in selective reabsorption of fitrate
   • Filtrate enters PCT
   • Walls consist of cuboidal epithelium with microvilli
   • see microvilli (brush border - BB) in PCT
   • Most of the filtrate (99%) is transported back to blood of peritubular capillaries
3. DCT (Distal Convoluted Tubule) - tubular secretion
   • Cells of DCT pump unwanted substances into urine from peritubular capillaries
   • Urine enters papillary duct
4. Nephron loop maintains solute gradient for concentrating urine

• See lab model Interactive kidney
• Cortex contains renal capsule + PCT + DCT
• Cortical nephrons (85%) vs juxtamedullary nephrons (15%)
  • Juxtamedullary nephron has long nephron loop (of Henle).
  • Cortical nephron has short nephron loop (of Henle) [See diagragm]
• Pyramid of medulla contains nephron loops + papillary ducts
  • Conteracts dehydration [conserves water; concentrates urine]
  • Long juxtamedullary nephron loop
    • Loop has descending tubule and ascending tubule
    • Countercurrent multiplier creates interstitial solute gradient in medulla
    • The longer the nephron loop, the greater the interstitial solute concentration
  • Papillary duct gives up water from descending urine to pyramid's higher solute concentration.
• Papillary duct (Collecting duct) is target for ADH [dehydration response]
  • ADH increases water permeability of collecting duct
  • Water moves from collecting duct to high solute interstitial fluid
  • Results in urine concentration