Tubular excretion
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Where does it take place?
Proximal and distal tubules of nephron
What takes place?
Cells of the tubules remove certain molecules and ions fro blood and actively deposit into the filtrate
Which ions move into the filtrate?
Hydrogen ions and potassium ions
What happens to the sodium ions?
Move back into the blood
What follows the sodium ions?
Water by osmosis
What other substances move into the filtrate?
Creatinine and uric acid
What happens to undesirable substances?
Actively excreted
What are undesirable substances?
Drugs, preservatives and colourants
Define PH
Measure of the hydrogen ion concentration in a solution – measure of acidity or alkalinity
What are large numbers of hydrogen ions produced by?
Metabolism
What does metabolism due to the pH?
Low is the pH
Why is it important that we have buffet systems?
To ensure pH remains in range in which the enzyme can function
PH of blood
7.35 / 7.45
PH of urine
6
Define buffer
Chemical substance that prevents too great a change in pH
What does the buffer do when the pH drops?
Binding with Hydrogen
What does the buffer do when the pH rises?
Release hydrogen
What does the buffers combine with that is excreted?
Combine with hydrogen ions to form compounds
How is homeostasis maintained with a buffer?
Hydrogen ions are got rid of and pH of blood is regulated
What is ammonia (NH3) synthesised by?
Epithelium cells of renal tubules
What does the ammonia react with?
Excess hydrogen to form ammonium ion (NH4)
What does the ammonia buffer regulate?
Acid-base balance