SECTION 2: MENSTRUATION AND THE CLINICAL MANIFESTATIONS OF THE PERIOD

Menstruation: Cyclical shedding of endometrium to bleed with cyclica ovulation. Regular menstruation is one of the signs of the mature reproductive function.

Regular cyclic, regarded as periodic preparations for fertilization & pregnancy, are called menstrual cycle, it is always 21-35 days.

Menstruation is normally painless & contains no clot （clot is dissolved by the fibrinolysin secreted by endometrial tissue）.

Usually the duration of menstrual is 3-5 days, and the average volume of blood lost is 30ml （20-60ml）. More than 80ml is considered abnormal. General menstrual period with no specific symptoms. Due to pelvic congestion, and the impact of prostaglandin, some women have lower abdominal or low back pain. Some even develop diarrhea and other symptoms of gastrointestinal dysfunction. A small number of patients can have a headache and mild neurological symptoms.

（王玎）