Loop of Henle

• Loop of Henle wall is one cell thick; thinner and thicker regions of loop reflect differences in lumen diameter, and different regions have different permeabilities to water, sodium and chloride ions

  A) permeable

  B) aquaporins

  C) impermeable

  D) permeable

  E) permeable

  F) facilitated

  G) active

  H) permeable

  I) permeable

  J) facilitated

  K) active

  
• Loop of Henle

  A) tubule

  B) H_2O

  C) sodium

  D) chloride ions

  E) Descending

  F) Na^+

  G) Cl^-

  H) water

  I) Descending

  J) osmosis

  K) capillaries

  L) H_2O

  M) Na^+

  N) Cl^-

  O) sodium

  P) chloride ions

  Q) Ascending

  R) Na^+

  S) Cl^-

  T) Na^+

  U) Cl^-

  V) active removal

  W) sodium

  X) chloride

  Y) Ascending

  Z) Distal convoluted tubule

  [) cortex

  \) Medulla

  ]) collecting duct

  ^) H_2O

  _) collecting duct

  `) osmosis

  a) capillaries

  b) H_2O

  c) urine

  d) collecting duct

  e) pelvis

  
• Loop of Henle

  • 1 cell thick wall
  • Thinner + thicker regions of loop
  • Reflect lumen diameter differences
  • Different regions have different permeabilities to water, sodium and chloride ions
  • Medulla region
  • Close to collecting ducts
  • Vasa recta (capillary network) lie adjacent
  • Increased salt concentration lowers medulla WP
  • More water reabsorbed from filtrate
  • Enters vasa recta blood capillaries
  • Hypertonic urine
  • Countercurrent multiplier system:
  • Hairpin arrangement (2 limbs close)
  • Fluid flows opposite directions
  • Longer loop greater countercurrent multiplier effect
• Descending Limb

  • Filtrate enters PCT isotonic to blood plasma, osmosis and facilitated diffusion occur
  • Causing filtrate to become high solute concentrated and hypertonic to blood plasma
  • Wall cell’s plasma membranes water permeable (aquaporins)
  • Water diffuses out filtrate by osmosis
  • Enters medulla
  • Slightly permeable to Na+ + Cl- ions
  • Slowly diffuse from medulla to filtrate by facilitated diffusion
• Ascending Limb

  • Wall cell’s plasma membranes are ion permeable but water impermeable
  • Water can’t follow ions from filtrate to medulla
  • Na+ + Cl- ions diffuse out to medulla in lower + thinner regions
  • In upper, thicker regions they’re actively pumped out
  • Net effect:
  • Top, filtrate hypertonic to blood (lower solute concentration)
  • Salty medulla tissue (Na^+ + Cl- ions); tissue fluid low WP
• Mammal adaptations for dry habitats

  • Longer loops of henle in deeper medulla tissue
  • Create higher salt concentration so more water re-absorbed
  • More permeable collecting ducts (ADH sensitive + more aquaporins in luminal membranes)
  • Metabolic water
  • Eat seeds with storage molecules like lipid
  • When aerobically respired, produces water
  • 1 lipid gram produces 2x more metabolic water than 1 carbohydrate gram