<P> Menstruation , also known as a period or monthly , is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina . The first period usually begins between twelve and fifteen years of age , a point in time known as menarche . However , periods may occasionally start as young as eight years old and still be considered normal . The average age of the first period is generally later in the developing world , and earlier in the developed world . The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women , and 21 to 31 days in adults ( an average of 28 days ) . Bleeding usually lasts around 2 to 7 days . Menstruation stops occurring after menopause , which usually occurs between 45 and 55 years of age . Periods also stop during pregnancy and typically do not resume during the initial months of breastfeeding . </P>
<P> Menstruation , also known as a period or monthly , is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina . The first period usually begins between twelve and fifteen years of age , a point in time known as menarche . However , periods may occasionally start as young as eight years old and still be considered normal . The average age of the first period is generally later in the developing world , and earlier in the developed world . The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women , and 21 to 31 days in adults ( an average of 28 days ) . Bleeding usually lasts around 2 to 7 days . Menstruation stops occurring after menopause , which usually occurs between 45 and 55 years of age . Periods also stop during pregnancy and typically do not resume during the initial months of breastfeeding . </P>
where does the blood come from when on period
where does the blood come from when on period
inner lining of the uterus
inner lining of the uterus