7.5. Borders of the Heart
The heart is described as having four borders. These are described below and are shown in the accompanying diagram.
Formed mainly by the right atrium.
Formed mainly by the left ventricle and part of the left auricle.
Formed mainly by the right ventricle.
Formed by both atria (where the great vessels leave the heart).
The important feature to note here is the inferior border of the heart is formed by the right ventricle, and this should give you an idea of the angle at which the heart lies at.