Formation of a Concentrated Urine

1
Formation of a Concentrated Urine
ADH present
900
Na Cl-
1100
Fig. 23.19 modified
2
Antidiuretic Hormonein the formation of a
concentrated urine
principal cell
Koeppen and Stanton, Renal Physiology
3
Medullary Gradient

• two solute hypothesis
• NaCl
• urea
• formation of gradient inhibited by
• osmotic diuresis
• The presence of unreabsorbed solutes decreases
  the concentration of Na, thereby decreasing the
  reabsorption of Na.
• protein deficiency
• less urea ? smaller medullary gradient
• loop diuretics

4
Functions of ADH

• Formation of a concentrated urine
• increased permeability of collecting duct to H2O
• increased permeability of collecting duct to urea
• increased reabsorption of NaCl by thick ascending
  limb of the loop of Henle

5
Posterior Pituitaryneurohypophysis
Fig. 17.4
6
Regulation of ADH Secretion
Stimulates hypothalamic osmoreceptors
? firing of atrial stretch receptors
Fig. 24.4
Fig 24.3
7
Diuretics Summary
Katzung, Basic and Clinical Pharmacology