Menstrual Cycle

**Semantic type:** Physiologic Function

**Definition:** The Menstrual Cycle involves regularly recurring hormonal changes and physiologic endometrial changes during the reproductive period in human females, and some primates, and culminates in partial sloughing of the endometrium (menstruation) in the absence of fertilization. For most women, one cycle takes 28 days. (NCI)

**Synonyms:** - menstrual cycle