A hiatal hernia does not cause many symptoms by itself, but when a sliding hernia occurs, the abnormal location of the gastroesophageal (GE) junction above the diaphragm affects its function and stomach contents can reflux into the esophagus.
-You need to work on sentence structuring. For example, when you wrote, The immigration, as a decision maked by a person is an act that occurs, because of some factors especially in the under developed countries and the most importants causes or reasons are mainly social reasons, politic reasons and economic reasons..
Immigration to the United States. Immigration to the United States is the international movement of individuals who are not natives or do not possess citizenship in order to settle, reside, study or to take-up employment in the United States. It has been a major source of population growth and cultural change throughout much of the history of the United States.