Pleural cavity: the cavity in the thorax that contains the lungs. Source: WordNet 2.1. Pleural cavity: cavity within the thoracic cavity consisting of the space between the parietal and visceral pleura; normally contains a capillary layer of serous fluid that lubricates the pleural surfaces.
Middle Class Average Income Range: $36,000 â $57,657. On a narrow view, a middle class family is said to have a mean average household income of $46,829 on a yearly basis. The numbers reflected on the 2010 Census showed that middle class average yearly income range from $36,000 â $57,657. Such figures fall on the third quintile.
1 Income Range: There are some economists who say that anyone who makes between $25,000 and $100,000 a year is middle class. That might be surprising to some, though.  Median Income: Others take a look at the median annual income, and then go $20,000 to either side. In 2010, the Census Bureau reports that the median income in the United States was $49,445, so if you go a little lower or higher, you get a middle class range of between about $30,000 and $70,000 a year.