Lecture Notes: Chapter 26, Lecture 2 - The Nephron

Overview of the Nephron

• Components:
  • Renal Corpuscle: Site of filtration
  • Renal Tubule: Pathway for fluid, where reabsorption and secretion occur
• Renal Tubule Parts:
  • Proximal Convoluted Tubule (PCT)
  • Loop of Henle (Nephron Loop)
  • Distal Convoluted Tubule (DCT)

Collecting and Papillary Ducts

• Collecting Ducts: Receive from multiple nephrons
• Papillary Ducts: Located at renal papilla, drain into renal pelvis

Loop of Henle & Nephron Types

• Structure:
  • Descending Limb
  • Thin Ascending Limb
  • Thick Ascending Limb
• Types of Nephrons:
  • Cortical Nephrons: 80-85%, primarily in cortex
  • Juxtamedullary Nephrons: 15-20%, longer loop in medulla

Blood Supply to Nephrons

• Afferent & Efferent Arterioles: Afferent is larger for increased pressure, site of filtration
• Peritubular Capillaries: Surround tubules, site of reabsorption/secretion
• Vasa Recta: Associated with Loop of Henle

Structure of the Renal Corpuscle

• Glomerulus: Capillary network
• Bowman’s Capsule: Consists of visceral (podocytes) and parietal layers

Juxtaglomerular Apparatus (JGA)

• Components:
  • Juxtaglomerular Cells (afferent arteriole)
  • Macula Densa (DCT)
• Function: Regulates blood pressure and glomerular filtration rate

Types of Cells in Nephron

• Podocytes: Visceral layer of Bowman’s Capsule, filtration slits
• Principal Cells (DCT): Receptors for ADH and aldosterone
• Intercalated Cells: Regulate blood pH
• Mesangial Cells: (To be discussed later)

Epithelia in Nephron Segments

• PCT: Simple cuboidal with microvilli
• Loop of Henle:
  • Descending: Simple squamous
  • Ascending: Simple cuboidal to columnar
• DCT & Collecting Ducts: Simple cuboidal

Functional Insights

• Nephron Count: Constant from birth, cannot be replaced
• Kidney Adaptability: Remaining kidneys compensate for loss

Goals for Understanding

1. Draw and label nephron parts
2. Describe nephron types
3. Explain JGA
4. Know function and location of nephron cell types