KINDEY FUNCTION 2

• What should students be able to define after studying the lecture topics?

  Clearance and its use in renal physiology

  
• How are glomerular filtration rate and effective renal plasma flow measured?

  By using specific clearance formulas
• What is osmolality?

  A measure of water concentration
• Why is osmolality important to renal function?

  It helps regulate water reabsorption in the kidneys

  
• What processes occur throughout the nephron for salt and water reabsorption?

  Reabsorption of sodium and water

  
• What is the function of the counter-current mechanism in the kidneys?

  It helps concentrate urine by creating a gradient

  
• What is the role of ADH at the collecting duct?

  It promotes water reabsorption

  
• What is the renal handling of potassium?

  It involves reabsorption and secretion processes

  
• How is renal clearance defined?

  The volume of plasma cleared of a substance in a given time

  
• What is the formula for renal clearance?

  $C =$$\frac{U \cdot V}{P}$

  
• If urine concentration is 35 mg/ml, urine volume is 0.9 ml/min, and plasma concentration is 0.25 mg/ml, what is the inulin clearance?

  $C_{inulin} =$$\frac{35 \cdot 0.9}{0.25} =$$126 \text{ ml/min}$
• Why is inulin used to measure GFR?

  It is freely filtered and not reabsorbed or secreted
• What is creatinine used for in clinical settings?

  To estimate GFR
• What does applying Fick’s principle to the kidney involve?

  Comparing the amount of substance entering and leaving the kidney
• What is the renal plasma flow approximately?

  ~600 ml/min
• How is renal blood flow calculated from renal plasma flow?

  By dividing renal plasma flow by the hematocrit
• What is the plasma sodium concentration range?

  135-145 mmol/l
• What is the main osmotically active solute in plasma?

  Sodium
• What percentage of filtered NaCl is reabsorbed in the proximal tubule?

  65%
• What is the role of the Na+:K+ ATPase pump in sodium reabsorption?

  It helps maintain sodium gradients across the tubule

  
• What is the osmolality range in plasma?

  285-295 mosm/kg

  
• How does the kidney generate concentrated urine?

  By separating sodium and water reabsorption

  
• What is the function of the countercurrent multiplier in urine concentration?

  It creates a high osmolality in the renal medulla

  
• What is the role of the vasa recta in the kidney?

  It helps maintain the medullary osmotic gradient

  
• What are the processes of salt and water reabsorption in the nephron?

  • Sodium reabsorption occurs mainly in:
  • Proximal tubule (65%)
  • Thick ascending limb (25%)
  • Distal tubule (2-5%)
  • Collecting duct (5%)
  • Water reabsorption is coupled to sodium reabsorption.

  
• What are the key components of the counter-current mechanism?

  • Countercurrent multiplier in the Loop of Henle
  • High osmolality in renal medulla
  • Vasa recta maintains osmotic gradient

  
• What are the main functions of the nephron in urine production?

  • Filtration of blood
  • Reabsorption of water and solutes
  • Secretion of waste products
  • Regulation of blood pressure and volume

  
• What is the importance of sodium balance in the body?

  • Linked to blood pressure regulation
  • Affects fluid balance
  • Influences kidney function
• What are the differences between osmolality and osmolarity?

  • Osmolality: measure of water concentration (mosm/kg)
  • Osmolarity: measure of water concentration (mosm/l)
  • Osmolality is temperature-independent
• What are the types of cells in the collecting duct and their functions?

  • Principal cells: Na+ transport
  • Intercalated cells: H+ transport

  
• What is the significance of the renal corpuscle in the nephron?

  • Site of blood filtration
  • Forms the initial filtrate
• How does the kidney maintain homeostasis?

  • Regulates electrolyte balance
  • Controls blood pressure
  • Adjusts urine concentration
• What are the effects of ADH on the kidneys?

  • Increases water reabsorption in the collecting duct
  • Concentrates urine

  
• What is the role of mitochondria in the nephron?

  • Provide energy for active transport processes
  • Support sodium reabsorption

  
• What is the significance of the Loop of Henle in urine concentration?

  • Reabsorbs more salt than water
  • Creates a concentration gradient in the medulla

  
• What is the relationship between urine osmolality and hydration status?

  • Higher urine osmolality indicates dehydration
  • Lower urine osmolality indicates overhydration

  
• What is the importance of the renal medulla's osmotic gradient?

  • Drives water reabsorption
  • Facilitates concentrated urine production

  
• What is the role of the thick ascending limb in sodium reabsorption?

  • Reabsorbs sodium via Na+:K+:2Cl- cotransporter
  • Impermeable to water

  
• How does the kidney respond to changes in blood pressure?

  • Adjusts filtration rate
  • Modulates sodium and water reabsorption

  
• What is the term for the fluid that is filtered from the blood in the kidneys?

  Filtrate