CBSE Class 9 Answered

Human heart is 4 chambered. The 2 upper, smaller chambers are the atria or auricles, whereas the lower, larger chambers are the ventricles. Atria are thin walled whereas the ventricles are thick walled.

Auricles receive blood and are the receiving chambers and ventricles transport blood, hence they are the conducting chambers.

Several blood vessels bring and carry blood to and from the heart. These include the pulmonary artery arising from the right ventricle, the pulmonary veins supplying to left ventricles and the systemic aorta arising from the left ventricle. In addition, the superior and inferior vena cava carries blood to right auricle. The right auricle opens into right ventricle by auriculoventricular opening, guarded by tricuspid valve. The left auriculoventricular opening is guarded by bicuspid valve. These valves prevent reflux of blood.

Opening of pulmonary arch is guarded by 3 semilunar valves called pulmonary valves.

The largest chamber of the heart, the left ventricle supplies oxygenated blood to various parts of the body through the systemic aorta, whose opening is guarded by 3 semilunar valves called aortic valves.

Inner surface of the ventricle walls shows small muscular folds called columnae carnae. The right and left ventricles are separated by inter ventricular septum whereas the right and left auricles are separated by inter auricular septum