What is shape of human heart?

Explanation

Atria are thin walled receiving chambers, form the anterior part of the heart. The right one is larger than the left, they are separated by inter-atrial septum. It has small pore in embryonic stage known as Foramen Ovale. Later it is closed and appears as a depression in the septum known as Fossa ovalis. If the foramen ovale does not close properly. It is called a patent foramen ovale.
The right atrium receives deoxygenated blood from different parts of the body (except the lungs) through three caval veins like two precaval veins and one post caval vein. The right atrium also receives blood from the walls of the heart through the coronary sinus, whose opening of the post caval vein is guarded by the value of inferior vena cavae or Eustachian valve. It directs the blood to the left atrium through the foramen ovale, in the fetal stage, but in the adults it becomes non functional.
The openings of the precaval veins into right atrium have no valves. The left atrium receives oxygenated blood from lungs through a pair of pulmonary veins, which opens into the left atrium through a common port. Atrio-ventricular septum atria and ventricles. It has right and guards the right atrio-ventricular opertures.
Tricuspid valve grauds the right atrio-ventricular aperture and bicuspid valve (mitral valve grauds the left atrio-ventricular aperture.