text: The<unk>  (or obtuse<unk>  is shorter than the right border of heart, full, and rounded: it is formed mainly by the left ventricle, but to a slight extent, above, by the left atrium.
  It extends from a point in the second left intercostal space, about 2.5 mm. from the sternal<unk> , obliquely downward, with a convexity to the left, to the apex of the heart.
option_0: Left margin of heart
option_1: Right border of heart
option_2: Diaphragmatic surface of heart
option_3: Sternocostal surface
option_4: Apex of the heart
option_5: Left sternal border
option_6: Sternal plane
option_7: Floating rib