QS Study

The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system. The heart size is estimated by comparing the transverse diameter of the cardiac silhouette with the transverse diameter of the thoracic cage seen on the frontal radiograph.

Surfaces – On its surface, it has several distinctive features which are of anatomical and clinical importance.

The heart has four surfaces –

a) Sternocostal (anterior) surface.

b) Diaphragmatic surface.

c) Right surface and

d) Left surface.

Sternocostal surface: The part of the sternocostal surface is uncovered by the left lung (cardiac notch) creating an area of superficial cardiac dullness.

  • Atrial portion: Formed mainly by the right atrium, right auricle and partly by the left atrium.
  • Ventricular portion: 2/3rd by right ventricle and 1/3 rd by the left ventricle.

Diaphragmatic surface: 2/3 rd formed by left ventricle and 1/3 rd formed by right ventricle. It’s created by the right and left ventricles that are divided from every other by the posterior interventricular groove.

Right surface: By right atrium.

Left surface: By left ventricle and partly by left atrium & its auricle. It’s created primarily by the left ventricle and partly by the left atrium and auricle. It’s directed upwards, backward, and to the left.

Fig: Different Surfaces and Borders of Heart


Superior border: Formed by the atrium (mainly by the left atrium). The upper border is obscured from the view on the sternocostal surface because ascending aorta and pulmonary trunk is located in front of it.

Inferior border: Formed by right ventricle and by left ventricle near the apex. This sharp, thin and nearly horizontal border extends from the lower limit of the right border to the apex. The inferior border separates the sternocostal surface from the diaphragmatic surface.

Right border: Formed by the right atrium. It extends from the right side of the opening of SVC to that of IVC and separates the base from the sternocostal surface.

Left border: Formed mainly by the left ventricle and slightly by the left auricle. It extends from the left auricle to the apex of the heart and separates sternocostal and left surfaces.


An apex of the heart is formed by the left ventricle. It is directed downward, forwards and to the left. It is is a conical area created by the left ventricle. It’s directed downwards and forwards and to the left.

It lies at the level of 5th left intercostal space, 9 cm from the midline, near or a little medial to the midclavicular line.

In the region of the apex, the apex-beat can usually be seen and palpated in the living subject.

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