Describe the structure of human heart.

Explanation

Heart.
1. It is a highly efficient, pumping organ of body. Human heart consists of 4 chambers: upper smaller right and left atria (auricles) with thinner wall and lower larger right and left ventricles with thicker walls.
2. Atria open into the respective ventricles by atrioventricular apertures guarded by atrioventricular valves.
3. The two atria are separated from each other by interatrial septum, and the two ventricles are separated from each other by interventricular septum.
4. The sinoatrial node (SAN) or the pacemaker is located in the upper wall of right atrium.
Valves of the heart
Valves are muscular flaps which prevent the blood to flow back through it. Two types of heart valves are distinguished :1. The Atrioventicular valves. These valves separate the atria from the ventricles. The right side of the heart possesses the tricuspid valve or right atrioventricular valve and the left side of the heart possesses the bicuspid or mitral valve.
2. Semilunar valves. These are located in the arteries leaving the heart. The pulmonary semilunar valves lies in the opening where the pulmonary trunk leaves the right ventricle and aortic semilunar valve lies at the opening between the left ventricle and aorta.