Anatomy and Physiology II

Urine Production and Osmotic Balance Lab , Page 1

Urinary Production and Osmotic Balance in the Body:

How much urine does the body produce and how salty is it?

Objectives

  • Test urine for presence of various metabolites and relate their presence or absence to kidney function.
  • Learn to analyze urine output, quantity and composition
  • Analyze lab data and relate it to conceptual understanding of kidney function

Lab Procedure and Data Gathering.

Here is a comparison of the different treatments or fluids we will be drinking.

Drink Treatment / Liquid / Sugar / Salts / Caffeine
1. Little Water / Low / None / Low / None
2. Lots of Water / High / None / Low / None
3. Sports Drink / High / Lots / High / None
4. Cola / High / Lots / Low / High
5. Caffeine-free Cola / High / Lots / Low or None / None
6. Diet Cola / High / None / Low / High

Comparing data from the following treatments will then help us see the effects of various components of the drinks:

  • Effect of liquid content: Compare little water versus lots of water
  • Effect of Sugar: Compare Diet Cola versus other colas
  • Effect of Salts: Compare Sports Drink versus other treatments
  • Effects of Caffeine: Compare Regular and Diet Cola versus Caffeine-free cola

During the course of lab, we will get urine production rates by colleting the amount of urine that is produced over a period of twenty minutes. We willl see how urine production changes every 30 minutes over the course of the lab.

1. Drink the fluids!

Decide which lucky “subjects” will drink which fluid treatment. The person who drinks a “little water” will drink half the bottle or 250 ml. Everyone else will drink a full bottle or 500 ml of their chosen drink. POUR AND DRINK YOUR FLUID NOW.

  1. Start at “zero” bladder volume.

Go the bathroom and void your bladder. Do not collect any of this urine.

  1. Urine collection and volume measurement.

Test subjects should take a 500 ml beaker, 100 ml graduated cylinder and hydrometer tube to bathroom. Other students just need a small urine sample cup.

Urine Sample: All students who wish to can collect a small sample of urine in a sample cup to check for metabolite presence and to spin down in the centrifuge for viewing in the microscope.

Urine Volume: The “test subjects” will also measure their total urine volume. This can all be done in the bathroom at the toilet using a 500 ml beaker (to collect the urine) and a 100 ml graduated cylinder to get the total volume of urine that you produce. Urinate into the beaker and then measure the volume in the graduated cylinder. If you need help reading a graduated cylinder, please ask before leaving for the bathroom. From the graduate cylinder, fill a hydrometer cylinder full of urine to bring back to class to test and measure specific gravity.

  1. Data from test subjects

Use this table to fill in YOUR raw data as you get it:

YOUR TREATMENT:
Time / Volume (ml) / Sp. Gravity
(salts) / pH / Glucose (g/dL)
30 minutes
60 minutes
90 minutes
120 minutes

Now calculate the filtration rate for all of the test subjects. Remember the filtration rate is just the amount of urine (in ml) divided by the time that has elapsed (in this case 30 minutes) to get ml/min. Also fill in Specific Gravity (SG) for each treatment and time.

Drink Treatment / 20 min. / 40 min. / 60 min. / 80 min.
Rate / S.G. / Rate / S.G. / Rate / S.G. / Rate / S.G.
1. Little Water
2. Lots of Water
3. Sports Drink
4. Cola
5. Caffeine-free Cola
6. Diet Cola

Now you can compare rates of filtration or how much liquid is being taken out of the body, as well as the salt concentration of the urine (how salty or concentrated it is).

What do your data suggest are the effects of each of the following and how does this match what your expectations would be?

  • Drinking more water
  • Drinking a sports drink
  • Drinking a caffeinated and sugared cola
  • Caffeine in the beverage
  • Sugar in the beverage

Can you make a graph that compares the filtration rate and specific gravity of the different treatments—this might help to more easily analyze your data.

  1. Urine Samples

Bring urine samples back to class and use a “dip stick” to check for salt content, presence of sugar, protein and various other elements.

Fill about half of a centrifuge tube (write your name on it) with urine and we will spin down all students’ samples to look at the sediment in the microscope. To view sediment, pour off urine, stain sediment with provided stain, use a pipette to spread a small amount of sediment on a slide and cover with cover slip. We might see crystals, white blood cells and bacteria—this is not a diagnostic lab!