It is a highly muscular triangular structure formed of special cardiac muscle. Its anterior part is broad and posterior part is somewhat conical. It has four chambers two auricles and two ventricles.
Auricle:
Auricle is the anterior part of the heart and dark in color. The two auricles are completely separated from one another and are known as right and left auricles.
The superior and inferior van-cava directly leads impure blood in the right auricle. The left auricle receives oxygenated blood from lungs by two pairs of pulmonary veins.
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Ventricle:
Behind the auricle, the ventricles are situated. It is formed of thick muscular wall, which is lighter in color. The left and right ventricles are separated by an oblique groove. From right auricle arise pulmonary aorta and carry impure blood to lungs. The left ventricle gives rise to caroticosystemic antero-dorsally.