How many chambers does the human heart have?

Hint: The heart is wrapped in a pericardial sac, filled with the serous membrane's parietal layers. The epicardium is formed by the visceral layer of its serous membrane. The heart wall is made by three layers of tissue. The epicardium is the exterior layer of the heart wall, the myocardium is the middle part, and the endocardium is the internal layer.

Complete answer:
- The heart is a fist-sized muscular organ situated just above and just left of the breastbone.
- The blood is pumped into the coronary system by heart, called the network of veins and arteries.
- To hold the fluid moving in one direction, pumps require a series of valves and the heart is no different. There are two kinds of valves in the heart that prevent blood circulating in the right direction.

The heart consists of four chambers:
- The right atrium collects and pumps blood from the veins to the right ventricle.
- Blood from the right atrium is collected by the right ventricle and injected into the lungs where it is filled with oxygen.
- The left atrium absorbs and pumps oxygenated blood from the lungs to the left ventricle.
- The left ventricle (the main chamber) pumps the remainder of the body with blood rich in oxygen.

Note: The coronary arteries pass along the heart's surface and supply the heart muscle with oxygen-rich blood. A nerve tissue network also passes through the heart, carrying out the complicated signals that control contraction and relaxation. A sac known as the pericardium covers the nucleus.