Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km (18,000 ft) of the troposphere. It is primarily composed of nitrogen (78%) and oxygen (21%) with only small concentrations of other trace gases.
Having irregular periods is very common. I see them in my practice all the time. The causes can range from something insignificant to something that requires treatment. For example, if you're a teen, your body's hormones can fluctuate and take some time until they find a balance.
Irregular periods: what does irregular mean? The average length of a Menstrual Cycle is around 28 days, and menstrual bleeding usually lasts between 2- 7 days. If your period varies from the average length and flow, your period may be irregular. Donât worry, irregular periods are common and a missed period does not always mean something serious.