Urinary System:  Renal Structures and Overview of Function

Urinary System: Fig 17.1

Kidney Layers
• Cortex
• Medulla
• Renal Pelvis
Fig 17.2

 

NEPHRONS
CORTICAL (80%)
JUXTAMEDULLARY (20%)

Vascular component:  Blood supply

Tubular:
Filtrate -----> Urine

Fig 17.4
Fig 17.7:  Simplified Nephron

Nephron Components:  Tubular
• Glomerulus & Bowman’s Capsule
    • Visceral and parietal layers of B.C.
• Proximal convoluted tubule (PCT)
• Loop of Henle
• Distal convoluted tubule (DCT)
• Collecting Duct

 

Nephron Components:  Vascular
• Afferent and efferent arterioles
• Peritubular capillaries
• Vasa recta

 

Cortical vs. Juxtamedullary Nephrons
 Note Locations in kidney
Peritubular vs. Vasa Recta capillaries
 
 

Fig 17.3:  The Nephron:
               Tubular Component
Fig 17.4:  Nephrons:
               Cortical & Juxtamedullary
Fig 17.6:  Blood Supply to Kidney
Fig 17.6:  Vascular Component of Nephron
Fig 17.5:  Juxtaglomerular Apparatus

Tubular Component:  Macula Densa
• Part of DCT
• Juxtaglomerular cells
• Cells of Afferent Arteriole
• Release renin in response to low renal BF and low tubular fluid [Na⁺] or [Cl^-]  content

 
 

Renal Processes
• Filtration
driven by hydrostatic pressure across a selectively permeable capillary
• Reabsorption
solutes moved from filtrate back into blood
• Secretion
solutes moved from blood into filtrate
filtrate becomes urine
Fig 17.7:  Renal Processes


 

Filtration
Fluid forced from plasma
Approx. 20% of plasma becomes filtrate
Filtrate becomes urine after modifications
Includes solutes small enough to pass through filter-membrane,  i.e., smaller than 69,000 MW

 
 

Reabsorption
Desireable substances in filtrate removed and returned to plasma
Active process

Secretion
Remaining undesirable substances in plasma transported into filtrate
Active process