Menstruation. Artwork of a uterus (upper centre) and its Fallopian tubes (upper left and right) and ovaries (round, end of tubes). These reproductive structures are partially dissected (at right) to show their appearance at the bleeding stage of the menstrual cycle. Blood is flowing through the neck (cervix) of the uterus, down into the vagina. Red blood cells (red) and cellular debris are seen in magnified view at lower centre. A corpus luteum gland (yellow) is seen in the sectioned ovary. It forms at the site of release of an egg, secreting hormones to prepare the uterus for pregnancy. If the egg is not fertilised, the blood-rich uterine lining is shed as seen.