Your kidneys are complex organs. They regulate the amount of water lost from the body and get rid of waste products, especially urea. Urea is made when any excess amino acids are broken down in your liver.
Middle Class Income for a Family. The annual average income for a middle class family of four is approximately $70, 354. This is based on a 2006 report by the U.S. Census for a family of four. This figure is in the middle of the range of incomes for this section of the population. The median income during this time for all households was $48,561.
The lower middle class consists of mostly blue-collar workers who make just enough to distinguish themselves from the poor or lower class. The average income for lower middle-class households is $29,204 as of September 2012, compared with the lower-class average of $23,550 for a family of four.