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.
Your menstrual cycle might be regular â about the same length every month â or somewhat irregular, and your period might be light or heavy, painful or pain-free, long or short, and still be considered normal. Within a broad range, normal is what's normal for you.racking your menstrual cycles can help you understand what's normal for you, time ovulation and identify important changes â such as a missed period or unpredictable menstrual bleeding. While menstrual cycle irregularities usually aren't serious, sometimes they can signal health problems.