Tigris–Euphrates river system through the central plain and combine at Al-Qurnah to form the Shatt al-Arab and discharge into the Persian Gulf. The region has historical importance as part of the Fertile Crescent region, in which civilization is believed to have first emerged. The ecoregion is characterized by two large rivers, the Tigris and Euphrates. The rivers have several small tributaries which feed into the system from shallow freshwater lakes, swamps, and marshes, all surrounded by desert. The hydrology of these vast marshes is extremely important to the ecology of the entire upper Persian Gulf. Historically, the area is known as Mesopotamia. As
Premenstrual water retention caused by high levels of circulating progesterone, estrogen, and prolactin, which stimulates secretory cells in the body. In the breasts, increased blood flow is also thought to be involved. Water retention and breast swelling can also be caused by hormonal contraceptives (which contain estrogen and/or a progestogen). According to three studies, fluid retention is not premenstrual, but rather peaks on the first day of menstrual flow. It also does not appear to be correlated to serum levels of progesterone or estradiol. Fluid retention is higher in recreational runners as compared to “normally active” women. Premenstrual water retention Premenstrual water retention