Received 5 December , in revised form 2. April Pergamon Press Ltd. Printed in Great Britain.
What are menstruation, periods, and PMS?
Women's Health Matters - The Female Body
Menstruation , also known as a period or monthly ,  is the regular discharge of blood and mucosal tissue known as menses from the inner lining of the uterus through the vagina. A lack of periods, known as amenorrhea , is when periods do not occur by age 15 or have not occurred in 90 days. The menstrual cycle occurs due to the rise and fall of hormones. The first menstrual period occurs after the onset of pubertal growth, and is called menarche.
14 Men and Women Get Very, Very Real About Period Sex
Healthy sexual and reproductive organs are vital to a woman's sexual health. Learning about the functions of each organ and how these organs work together allows you to be aware of your body and of any changes that might indicate a problem. This information can also help you choose a method of birth control or determine when is the best time to try and get pregnant.
According to the dual sexuality hypothesis, women form pair-bond relationships with men who provide care but also obtain genetic benefits by biasing mating effort towards men with high-fitness genes during the fertile phase. By contrast, the commitment hypothesis proposes that attachment bonds with primary partners function to strengthen pair-bond relationships by enhancing in-pair attraction at the fertile phase, rather than extrapair attraction. We employed 1 a urinary luteinizing hormone test to determine the day of ovulation, 2 a 5-part classification of menstrual cycle that identifies a distinct peri-ovulatory phase, and 3 individualized phase identification for each participant. There was a mid-cycle rise in extrapair sexual desire. Women gave and received more care from partners during the menstrual than the mid-cycle phases.