The diaphragm is both a muscular and tendinous tissue that begins to bear mechanical pressure from the abdominal vis- cera during the tenth week of life. Abnormal diaphragmatic development can lead to large congenital diaphragmatic hernias present at birth, while other smaller areas of dia- phragmatic weakness can enlarge over time and become apparent later in life. Hiatal hernias result from a widening of the diaphragmatic crura and a weakening of the phre- noesophageal membrane. This results in a protrusion of a hernia sac containing intra-abdominal organs through the diaphragmatic hiatus and into the mediastinum. The preva- lence of large hiatal hernias increases with age, suggesting that environmental and tissue-aging factors are involved in the pathophysiology. In addition, there is a positive asso- ciation between the presence of hiatal and inguinal hernias, suggesting either a genetic predisposition affecting tissue integrity or some other common factor, such as increased intra-abdominal pressure.
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