Session 3

Question 1

Function of the kidneys

Answer 1

Function of the Kidney
• Regulation: controls concentrations of key substances in ECF
• Excretion: excretes waste products
• Endocrine: synthesis of renin, erythropoietin, prostaglandins
• Metabolism: active form of Vitamin D, catabolism of insulin, PTH calcitonin

Question 2

Which substances are reabsorbed in the kidney

Answer 2

Over 99% of filtered water recovered • Over 99% of filtered sodium and
chloride ions recovered • 100% of bicarbonate recovered • 100% of glucose and amino acids
recovered • Just a few waste products not
recovered • Some substances (e.g. H+, actively
secreted, so lose more than filtered)

Question 3

What substance is filtered by the kidney

Answer 3

Kidney filters very large amount of
extracellular fluid (ECF)
• Ultra filtrate – water, ions all small
molecules • 180 L/day – every L filtered over ten times
a day
• And then recovers nearly everything
• Leaving on average about 1.5 L per day
of urine

Question 4

Overview of fluid in the body, which part is directly regulated by the kidney

Answer 4

70 kg man has 42 litres of water (60%water). 2/3 of that is ICF so ICF is 28 litres. The other 1/3 is ECF so ECF is 14 litres. The elf is divided again as 75% interstitial water (10.5 litres) and 25% intravascular plasma (3.5 litres). Red blood cells make up the other 2 litres of the 5.5 litres of the circulating volume.