A cell model for renal synthesis and excretion of ammonia. Ammonium ions are formed from glutamine in the cell and are secreted into the tubular urine (top). H+ from H2CO 3 (bottom) is consumed when a-ketoglu-tarate is converted into glucose or CO2 and H2O. New HCO3~ is added to the peritubular capillary blood—1 mEq for each mEq of NH4+ excreted in the urine.
eral days. Enhanced renal ammonia synthesis and excretion is a lifesaving adaptation because it allows the kidneys to remove large H+ excesses and add more new HCO3~ to the blood. Also, the excreted NH4+ can substitute in the urine for Na+ and K+, diminishing the loss of these cations. With severe metabolic acidosis, ammonia excretion may increase almost 10-fold.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.