Structure of Heart in animals

The heart is an involuntary muscular organ which occupies the greater part of the middle mediastinal space. Its shape is an irregular and somewhat flattened cone.

It is attached at the base by the great blood vessels but otherwise it is free in the pericardium.

Structure of Heart is asymmetrical in position as more of it lies to the left of the median plane. The long axis is directed ventrally and backward.

The heart presents two surfaces, two borders, a base and an apex.

The base lies opposite to the lateral wall of thorax from the second intercostal space to the sixth rib.

The apex lies to the left above the sternum at the sixth interchondral space.

The anterior border is strongly convex whereas the posterior border is shorter, nearly vertical and is opposite the fifth intercostal space.

The two surfaces, the right and left are convex and marked by grooves, which indicate the division of the heart into four chambers.

The coronary or transverse groove indicates the division between the atria and ventricles. It almost completely encircles the heart except at the origin of the pulmonary artery.

The longitudinal grooves are left anterior and right posterior in position. The left groove begins at the coronary groove behind the origin of the pulmonary artery and descends down almost parallel to the posterior border.

The right groove begins at the coronary groove below the termination of the posterior vena cava and passes towards the apex but does not reach the apex. There is another intermediate groove, a shallow one that extends from the coronary groove on the wall of the left ventricle but does not reach the apex.

Coronary vessels and fat occupy the grooves.

The average weight of the heart in ox is 2.5 kg, i.e. 0.4% -0.5% of body weight.

The interior of the heart is divided by a complete septum into a right and left halves. Each half is subdivided into an upper atrium and a lower ventricle. The division is indicated externally by grooves.