Female sex hormones in the bloodstream. Animation of sex hormones (yellow) circulating in the bloodstream with red blood cells (one white blood cell is also shown). The hormones shown here include luteinizing hormone and follicle-stimulating hormone, both released by the pituitary gland in the brain. The roles of these hormones in the female reproductive system include triggering and maintaining the process of ovulation, the maturation and release of female sex cells from the ovaries. These hormones act on ovarian tissue, prompting the release of further sex hormones that act together to control ovulation. This animation is part of a sequence illustrating the female reproductive system, ovulation, fertilisation and pregnancy. For the continuation of this animation, see clip K005/5514.