The active transport of sodium chloride by the ascending loop of Henle is independent of antidiuretic hormone (ADH) and causes a progressive concentration of the interstitial fluid of the medulla but a dilutio nof the luminal fluid. ADH increases the permeability of the corical collecting ducts to water, and so water is reabsorbed by this segment until the luminal fluid is isoosmotic to cortical interstitial fluid. The luminal fluid then enters and flows through the medullary collecting ducts and the concentrated medullary interstitium causes water to move out of these ducts, made highly permeable to water by ADH. The result is the concentration of the collecting duct fluid and the urine. Renal sodium regulation: Sodium excretion is the difference between the amount of sodium filtered and the amount reabsorbed. The major control of tubular sodium reabsorption is the adrenal cortical hormone aldosterone, which stimulates sodium reabsorption in the cortical collecting ducts. Renal water regulation Water excretion is the difference between the amount of water filtered and the amount reabsorbed. ADH mediates water absorption which is controlled by baroreceptors and osmoreceptors of the posterior pituitary. Via the baroreceptor reflexes, a low extracellular volume stimulates ADH secretion and a high extracellular volume inhibits it. Via the osmoreceptors, a high body-fluid osmolarity stimulates ADH secretion and a low osmolarity inhibits it. Homeostatic control of hydrogen ions by renal mechanisms The kidneys maintain a stable plasma hydrogen ioin concentration by regulating plasma bicarbonate concentration. They can either excrete bicarbonate or contribute new bicarbonate to the blood. Bicarbonate is reabsorbed when hydrogen ions, generated in the tubular cells by a process catalysed by carbonic anhydrase, are secreted into the lumen and combine with filtered bicarbonate. The secreted hydrogen ions are not excreted in this situation. In contrast, when the secreted hydrogen ions comine in the lumen with filtered phosphate or other non-bicarbonate buffer, they are excreted and the kidneys have contributed new bicarbonate to the blood. The kidneys also contribute new bicarbonate to the blood when they produce and excrete ammonia. Solution The active transport of sodium chloride by the ascending loop of Henle is independent of antidiuretic hormone (ADH) and causes a progressive concentration of the interstitial fluid of the medulla but a dilutio nof the luminal fluid. ADH increases the permeability of the corical collecting ducts to water, and so water is reabsorbed by this segment until the luminal fluid is isoosmotic to cortical interstitial fluid. The luminal fluid then enters and flows through the medullary collecting ducts and the concentrated medullary interstitium causes water to move out of these ducts, made highly permeable to water by ADH. The result is the concentration of the collecting duct fluid and the urine. Renal sodium regulation: S.

1. The active transport of sodium chloride by the ascending loop of Henle is independent of
antidiuretic hormone (ADH) and causes a progressive concentration of the interstitial fluid of the
medulla but a dilutio nof the luminal fluid. ADH increases the permeability of the corical
collecting ducts to water, and so water is reabsorbed by this segment until the luminal fluid is
isoosmotic to cortical interstitial fluid. The luminal fluid then enters and flows through the
medullary collecting ducts and the concentrated medullary interstitium causes water to move out
of these ducts, made highly permeable to water by ADH. The result is the concentration of the
collecting duct fluid and the urine.
Renal sodium regulation:
Sodium excretion is the difference between the amount of sodium filtered and the amount
reabsorbed. The major control of tubular sodium reabsorption is the adrenal cortical hormone
aldosterone, which stimulates sodium reabsorption in the cortical collecting ducts.
Renal water regulation
Water excretion is the difference between the amount of water filtered and the amount
reabsorbed. ADH mediates water absorption which is controlled by baroreceptors and
osmoreceptors of the posterior pituitary. Via the baroreceptor reflexes, a low extracellular
volume stimulates ADH secretion and a high extracellular volume inhibits it. Via the
osmoreceptors, a high body-fluid osmolarity stimulates ADH secretion and a low osmolarity
inhibits it.
Homeostatic control of hydrogen ions by renal mechanisms
The kidneys maintain a stable plasma hydrogen ioin concentration by regulating plasma
bicarbonate concentration. They can either excrete bicarbonate or contribute new bicarbonate to
the blood. Bicarbonate is reabsorbed when hydrogen ions, generated in the tubular cells by a
process catalysed by carbonic anhydrase, are secreted into the lumen and combine with filtered
bicarbonate. The secreted hydrogen ions are not excreted in this situation.
In contrast, when the secreted hydrogen ions comine in the lumen with filtered phosphate or
other non-bicarbonate buffer, they are excreted and the kidneys have contributed new
bicarbonate to the blood. The kidneys also contribute new bicarbonate to the blood when they
produce and excrete ammonia.
Solution
The active transport of sodium chloride by the ascending loop of Henle is independent of
antidiuretic hormone (ADH) and causes a progressive concentration of the interstitial fluid of the
medulla but a dilutio nof the luminal fluid. ADH increases the permeability of the corical

2. collecting ducts to water, and so water is reabsorbed by this segment until the luminal fluid is
isoosmotic to cortical interstitial fluid. The luminal fluid then enters and flows through the
medullary collecting ducts and the concentrated medullary interstitium causes water to move out
of these ducts, made highly permeable to water by ADH. The result is the concentration of the
collecting duct fluid and the urine.
Renal sodium regulation:
Sodium excretion is the difference between the amount of sodium filtered and the amount
reabsorbed. The major control of tubular sodium reabsorption is the adrenal cortical hormone
aldosterone, which stimulates sodium reabsorption in the cortical collecting ducts.
Renal water regulation
Water excretion is the difference between the amount of water filtered and the amount
reabsorbed. ADH mediates water absorption which is controlled by baroreceptors and
osmoreceptors of the posterior pituitary. Via the baroreceptor reflexes, a low extracellular
volume stimulates ADH secretion and a high extracellular volume inhibits it. Via the
osmoreceptors, a high body-fluid osmolarity stimulates ADH secretion and a low osmolarity
inhibits it.
Homeostatic control of hydrogen ions by renal mechanisms
The kidneys maintain a stable plasma hydrogen ioin concentration by regulating plasma
bicarbonate concentration. They can either excrete bicarbonate or contribute new bicarbonate to
the blood. Bicarbonate is reabsorbed when hydrogen ions, generated in the tubular cells by a
process catalysed by carbonic anhydrase, are secreted into the lumen and combine with filtered
bicarbonate. The secreted hydrogen ions are not excreted in this situation.
In contrast, when the secreted hydrogen ions comine in the lumen with filtered phosphate or
other non-bicarbonate buffer, they are excreted and the kidneys have contributed new
bicarbonate to the blood. The kidneys also contribute new bicarbonate to the blood when they
produce and excrete ammonia.