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Vein, in anatomy, blood vessel that conducts the deoxygenated blood from the capillaries back to the heart. Three exceptions to this description exist: the pulmonary veins return blood from the lungs, where it has been oxygenated, to the heart; the portal veins receive blood from the pyloric, gastric, cystic, superior mesenteric, and splenic veins and, entering the liver, break up into small branches that pass through all parts of that organ; and the umbilical veins convey blood from the fetus to the mother's placenta. Veins enlarge as they proceed, gathering blood from their tributaries. They finally pour the blood through the superior and inferior venae cavae into the right atrium of the heart. Their coats are similar to those of the arteries, but thinner, and often transparent.
Veins are blood vessels that return blood to the heart from other parts of the body. This false-color electron micrograph shows red blood cells packed into a capillary, the smallest type of blood vessel. Blood flows from the capillaries into veins after oxygen has been exchanged.
HISTORY OF HOSPITALS:
Today the United States is home to 6,021 hospitals that contain over 1 million hospital beds. U.S.hospitals annually admit some 34 million patients who are assigned a bed and receive medical or surgical treatment as inpatients. Hospitals also provide outpatient treatment in clinics or other walk-in, or ambulatory, settings for an additional 483 million patients every year.
Hospitals in the United States are classified by the services they provide (general or specialized), the length of stay they offer patients (short stay or long-term care), and by their ownership (not-for-profit, proprietary, or government owned). Although most U.S. hospitals are classified as not-for-profit, any one hospital will fall into several of the above categories. For example, Methodist Hospital in Houston, Texas, with more than 300,000 sq m (3 million sq ft) of space, is one of the largest short-stay, not-for-profit, general hospitals in the country.
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HISTORY OF HOSPITALS
