Learning Objectives

• Describe the change in osmolarity in different segments of a nephron
• Describe the urine concentrating mechanisms
• Describe the urine diluting mechanisms
• Explain the role of ADH in urine formation
• Discuss the countercurrent multiplier and exchanger systems
• State the significance of vasa recta in the formation of concentrated urine

Urine Osmolarity & ADH

• what is the osmolality of urine?
• how much urine is formed each day?
• how does osmolarity change throughout the nephron?
• how is this different in the presence of ADH?
• what stimulates ADH secretion?
• what are the actions of ADH?
• what aquaporins are found in the nephron?
• what is water diuresis vs osmotic diuresis?
• how does ADH form concentrated urine?

Urine Volumes

• what is obligatory vs facultative water reabsorption?