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
Body water ocular fluids. Adipose tissue contains about 10% of water, while muscle tissue contains about 75%. In "Netter's Atlas of Human Physiology", body water is broken down into the following "compartments:" Total body water can be determined using Flowing afterglow mass spectrometry measurement of deuterium abundance in breath samples from individuals. A known dose of deuterated water (Heavy water, DO) is ingested and allowed to equilibrate within the body water. The FA-MS instrument then measures the deuterium-to-hydrogen (D:H) ratio in the exhaled breath water vapour. The total body water is then accurately measured from the increase in breath deuterium content in