A single Regional Dressage Championship program organized by the United States Dressage Federation (USDF), and recognized by the United States Equestrian Federation, Inc. (USEF), will be held in each of the nine USDF.
If fertilization and/or implantation does not take place, the system is designed to menstruate (the monthly shedding of the uterine lining). In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.
The female reproductive system interacts with many other systems in the body. The most common is the endocrine system. The reproductive system relies on the endocrine system to produce hormones such as progesterone and estrogen, that help with the blood lining of the uterus and prepare the uterus for pregnancy. Another system would have to be the nervous system.