The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter the blood to remove waste and produce about 1-2 liters of urine per day. Rapid weight loss can cause the kidneys to drop in position and kink the ureters, backing up urine and potentially damaging the kidneys. Urine is formed through glomerular filtration, tubular reabsorption, and tubular secretion in functional units of the kidneys called nephrons. The urinary bladder stores urine temporarily until urination, when it is passed through the urethra out of the body.

1. Urinary System

2. Organs Kidneys Paired ureters Urinary Bladder Urethra http://static.howstuffworks.com/gif/define-kidneys-and-urinary-system-1.jpg

3. Kidneys Extend from the T12 to L3 vertebrae Right is slightly lower because of the liver 12cm long and 6 cm wide http://www.engin.umich.edu/~cre/web_mod/viper/pics/kidneys2.bmp

4. Kidneys and Weight Loss Rapid weight loss causes fat around kidneys to dwindle Kidneys drop to a lower position (ptosis) Ureters become kinked Urine cannot pass through the ureters- it backs up and can cause kidney damage

5. Nephrons The structural and functional units of the kidneys Form urine http://www.auburn.edu/academic/classes/zy/hist0509/image/nephron_colorfinal.jpg

6. Urine Formation Glomerular filtration Tubular reabsorption Tubular secretion http://www.mhhe.com/biosci/ap/dynamichuman2/content/gifs/0178A.gif

7. Urine 1.0 to 1.8 liters is produced every 24 hours Contains nitrogenous waste and unneeded substances More solutes = deeper color Usually slightly acidic Sterile

8. Urinary Bladder Stores urine temporarily Bladder wall contains three layers of smooth muscle Collapses when empty

9. Urethra Carries urine from the bladder to outside the body Length and relative function differ by sex Female: 3-4 cm: conduct urine to the body exterior Male: 20cm: urine out of the body and ejects sperm from the body