The Menstrual Cycle

Also called

menstrual cycle · menstruation · ovarian cycle · uterine cycle · follicular phase · luteal phase · ovulation · LH surge · FSH · oestrogen · estrogen · progesterone · Graafian follicle · corpus luteum · endometrium · hCG · मासिक चक्र · अंडोत्सर्ग · पीत पिंड

Topics

• The menstrual cycle repeats about every 28 days, from menarche at puberty to menopause around 50.
• Days 1–5, menstrual phase: the thick endometrium breaks down and leaves the body with blood.
• Follicular phase: FSH and LH make a follicle grow into a Graafian follicle that secretes oestrogen.
• Oestrogen makes the endometrium regenerate and thicken (the proliferative phase).
• A sharp LH surge in mid-cycle makes the Graafian follicle rupture and release the ovum, about day 14.
• Luteal phase: the empty follicle becomes the corpus luteum, which secretes a lot of progesterone.
• Progesterone keeps the endometrium thick and ready for an embryo to implant.
• Without fertilisation the corpus luteum degenerates, progesterone falls and the lining is shed again.
• In pregnancy the embryo makes hCG, which keeps the corpus luteum, so the lining stays and no period comes.

About this model

A GLB file of about 645 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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