Choose the odd one out from the following set, giving the reason for your choice.
Mitral valve, sino-atrial node, aorta, pulmonary vein.

Sino-Atrial node:

1. A myocardial structure that is present near the opening of the vena cava at the corner right auricle is known as the Sino-Atrial node (SA node).
2. The SA node generates impulses that stimulate contraction.
3. Due to its function, the SA node is called a pacemaker.

Location of others - left side of the heart:

1. The mitral or bicuspid or left atrioventricular valve is located between the left atrium and the left ventricle.
2. The aorta is the artery that arises from the left ventricle and supplies blood to the whole body.
3. The pulmonary vein is the vein that carries blood from the lungs to the left auricle.