Expert: John Locke - 8/21/2010

Question
Hello
I need help on a question that I cannot seem to answer accurately and I was wondering if you could help? There seems to be more than one answer and I’m confused.
The question is!
Explain the excretory function of the urinary system?


Answer
Thanks for using AllExperts. The excretory function of the urinary system refers to the removal of wastes from the body by the kidneys in the form of urine. The kidneys filter the liquid part of the blood many times per day and extract toxic and unwanted chemicals that pass out of the body in the urine. The kidneys may filter the liquid portion of the blood 20 times per day or more; with each pass through the kidneys, substances move from the bloodstream to the kidney filtration system. Within this system--the nephrons--useful substances are saved and reabsorb back into the bloodstream. Useless wastes or excess amounts of useful substances don't get reabsorbed and so pass out of the body in the urine.

The following substances are not useful to the body and are excreted by the kidneys:
Nitrogen, in the form of a chemical called urea
Nitrogen in the form of ammonia
Free acids that are used to balance the pH of the blood
Drugs that have been broken down by the liver
Uric acid from the breakdown of DNA

As I noted above, some substances that are useful to the body get excreted by the kidneys because there is simply too much of them in the bloodstream for the kidneys to hold onto it all.

The chemical glucose is a good example of this. People with diabetes suffer from an uncontrolled, high level of glucose in their bloodstream. When their blood is filtered through the kidneys, some of this glucose escapes into the urine because there is too much for the kidneys to handle. Hence, glucose in the urine is typically a sign of active diabetes.

I will be happy to answer follow up questions if you have any.