On a hot day, a person drinks 3.0 L, and makes 0.2 L of water in metabolism…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
On a hot day, a person drinks L, and makes L of water in metabolism. The losses other than urine are L from the skin without sweat, L from the lungs, L in the faeces and L in sweat. The body water stays the same.
- What is the total water gained?
- What is the total water lost by routes other than urine?
- How much urine does the person pass?
Need a reminder? The key ideaShow
The lungs remove CO at about mL a minute, and water. The liver removes bile pigments, cholesterol, steroids, vitamins and drugs in the bile. Sweat has water, NaCl, a little urea and lactic acid, and it cools the body. Sebum has sterols, hydrocarbons and waxes. Saliva has small amounts of nitrogenous wastes. The water gained in a day equals the water lost: the urine is the part that the kidneys adjust.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Drinks: L. Metabolic water: L. Other losses: , , and L.
Plan. Gains must equal losses. The urine is the rest.
Step 1. Gains. L.
Step 2. Other losses. L.
Step 3. Urine. L.
Answer: L; L; L.
Check. The urine is less than on a normal day, because the sweat takes so much water.
Source. The normal values are from Guyton and Hall, Textbook of Medical Physiology, 14th edition. They are not in NCERT.
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