Kidney function

Question 1

Give four substances that cross the glomerular basement membrane

Answer 1

Water
Electrolytes
Urea
Creatinine

Question 2

Give two substances that cross the GBM but are reabsorbed in the proximal tubule

Answer 2

Glucose

Low molecular weight proteins

Question 3

Give two things that cannot cross the GBM (in health)

Answer 3

Cells (WBCs, RBCs)

High molecular weight proteins (albumin, globulins)

Question 4

How does parathyroid hormone (PTH) affect kidney function?

Answer 4

PTH reduces the number of sodium-phosphate co-transporters in the proximal tubule apical membrane.
This reduces reabsorption of phosphate
More phosphate is therefore excreted in urine
This reduces serum levels of phosphate
(Phosphate binds calcium; high phosphate causes a drop in serum free calcium, which stimulates production of PTH. Therefore, the action of PTH on the kidney helps to restore calcium levels to normal)