Cardia is the part of the stomach pointing towards the oral cavity, including the esphageal junction.
In the cardial region the double layered muscles of the esophagus give way to the triple layerd muscles of the stomach. The spiral muscle loops ("Musculus sphincter cardiae") in this region prevent the reflux of stomach contents into the esophagus with their contractions.
Histologically, one can see the transition from the multilayer squamous eithelium of the to the single layer cylindric epithelium of the stomach. The mucous glands in the area of the Cardia are called Die im Bereich der Kardia vorkommenden mukösen Drüsen cardia glands.