The Human Heart
The heart starts to beat practically at conception and continues it’s life-sustaining role for a hundred years or longer. It’s size and mass are proportional to each person, our hearts being roughly the size of our clenched fist. This durable muscle powers the circulatory system that pumps blood into the lungs, exchanging CO2 for oxygen.
The heart is positioned in front of the T5-T8 vertebrae of the spinal cord behind the sternum, and it’s monitored by the parts of the brain stem that control the involuntary workings of the respiratory, digestive, and lymphatic systems.
As the heart is pounding away and keeping us healthy its protected by the sternum and ribcage and encased within the pericardial sac. The outside of the double-layered pericardium is a tough membrane attached to the inner wall of the chest cavity to prevent the heart from shifting around. The inner pericardium is connected to the heart by a thin layer of connective tissue and fat. In between is the pericardial fluid that forms a cushion to lubricate the heart and prevent infection.
Despite it’s vital function, the structure of the heart isn’t complicated … a right and left atria, a right and left ventricle, four valves, and the surrounding arteries and veins of the circulatory system
A Single Heartbeat
A heartbeat begins when an electrical “spark” generated by specialized cells within the heart causes the atria and ventricles of the heart to contract in a precisely timed rhythm. Simply put, the right side of the heart receives and pumps deoxygenated blood into the lungs, while the left side receives the re-oxygenated blood and pumps it out to the systemic circulation.