- Heart: hollow muscular organ in the mediastinum, enclosed in the pericardium; pyramidal, placed obliquely with one-third to the right and two-thirds to the left of the median plane.
External Features
- Four external features: apex, base, three surfaces (sternocostal, diaphragmatic, left), and four borders (right, left, inferior, upper).
sternocostal (anterior) surface of the heart Sternocostal (anterior) surface of the heart.