HENNING DALHOFF / SCIENCE PHOTO LIBRARY HENNING DALHOFF / SCIENCE PHOTO LIBRARY
Ovarian cycle, computer artwork. Once sexual maturity is reached up to 20 oocytes start developing into eggs (ovums) every menstrual cycle. Only one will reach full maturity as a Graafian follicle (right) and release its egg at ovulation (bottom right). The follicle then develops into a corpus luteum (yellow), which secretes progesterone to build up the lining of the uterus, ready for a fertilised egg. If there is no fertilised egg after 12 days it stops secreting and degenerates into a corpus albicans (left).
Model release not required. Property release not required.