Teacher Resource
Dry lab – The Urinary System Exposed!
Course: SBI4U, Strand E. Homeostasis
Overall expectations: E2, E3
Specific expectations: E2.1, E3.1, E3.3
Instructions
Have students complete the dry lab individually. It should take only one period, or be finished
for homework. We recommend collecting and evaluating it under Thinking & Inquiry and
Communication.
This lab should be assigned after students have learned about the nephron and urine
formation.
Limitations
This lab has a small data set and therefore, data interpretation is limited. It was developed
mainly to deal with the function of the nephron and one chemical substance’s effect (alcohol)
on the urinary system. There is room for expanding the exercise to include additional
substances, such as caffeine.
Special Needs Modifications
Students with special needs should use assistive technology to complete the assignment.
Students may also work in pairs and learn together.
Sources
Lab Exercise 7.5.1 - Comparing Solutes in the Plasma, Nephron and Urine (Student Worksheet),
Nelson, 2003
Basic Answer Key
Part A – see diagram of nephron in Nelson Biology 12 textbook or online
Part B
a. Protein & substance X were not filtered into the nephron because they are not present in the
Bowman’s capsule but are present in the glomerulus.
b. Yes, glucose would be found in the glomerulus because it is present in the blood stream.
c. Increase because urea and ammonia are collected in the nephron. Ammonia is also transported
into the proximal tubule from the blood.
d. Bicarbonate (HCO3-) also follows Na+ ions into the blood. In addition, potassium (K+) are
transported into the nephron so some Cl- and HCO3- remains in the nephron to balance the
charge.
e. Red blood cells/platelets – they are too large to be filtered into the Bowman’s capsule
f.
No – veins carry nutrients as well. They carry whatever is reabsorbed from the nephron.
g. Lower concentrations of solutes in blood and nephron due to higher volume of H2O.
Part C
a. Increasing the permeability increases the concentration of solutes in urine by allowing water to be
reabsorbed into the blood (decreases urine production).
b. This is negative feedback because when body is low on H2O, ADH is released and causes the body
to conserve water.
c. Diagrams will vary but should include osmoreceptors, pituitary gland, change in osmotic pressure,
etc.
d. The volume of urine produced will increase and the concentration will decrease. However, the
concentration of solutes in the blood will continue to increase, meaning the blood osmotic
pressure will continue to increase. The diagram should show effect of alcohol on ADH.