It also affects the nervous system of the cow, causing restlessness and most importantly, the willingness to be mounted by other animals. Estrogen causes the uterus to contract, allowing sperm to be transported through the female reproductive tract more efficiently after insemination. Other effects of high estrogen concentrations in the blood include increased blood flow to the genital organs and the production of mucus by glands in the cervix and vagina. These characteristics are all signs of estrus, or sexual receptivity. Progesterone produced by the CL prevents cyclicity by acting on the anterior pituitary in a negative feedback fashion; therefore, decreasing the release of FSH and LH. It prepares the uterus for reception of fertilized ova and subsequent pregnancy. It also helps the cow maintain pregnancy by suppressing uterine contractions and promoting development of the uterine lining.Last important hormone is prostaglandin F.2a(PGF2a) which is secreted by the endometrium of the uterus, it affects structures on the ovary, helping to initiate ovulation by causing the demise of the CL, which results in withdrawal of progesterone's negative feedback mechanism.