A blister is a bubble of fluid under the skin. The clear, watery liquid inside a blister is called serum. It leaks in from neighboring tissues as a reaction to injured skin. If the blister remains unopened, serum can provide natural protection for the skin beneath it. Small blisters are called vesicles. Those larger than half an inch are called bullae. A blood blister is filled with blood, rather than serum.
With 15,145 people, Cullman is the 41st most populated city in the state of Alabama out of 578 cities. But watch out, Cullman, because Alexander City with 14,849 people and Scottsboro with 14,748 people are right behind you.
Jefferson County is Alabamaâs economic and cultural center. With a 2015 population estimate of 662,843, Jefferson County contains the stateâs largest city â Birmingham (2015 population estimate of 210,838) and the stateâs sixth largest city â Hoover (2015 population estimate of 85,712). Jefferson County is ranked among the top 100 most populated counties in the United States. The Birmingham central business district has a daytime business population of more than 80,000 and contains two major employment districts â the medical district and the financial district.