Function of the Heart
The heart pumps blood through our immense and complicated circulatory systems at high pressure. It is a truly impressive feat of engineering, as it must circulate about five liters of blood through a full 1,000 miles worth of blood vessels each minute! We will talk more about how the heart accomplishes this remarkable task under the “Heart Structure” section below.
The pumping action of the heart allows the movement of many substances between organs in the body, including nutrients, waste products, and hormones and other chemical messengers. However, arguably the most important substance it circulates is oxygen.
Oxygen is required for animal cells to perform cellular respiration. Without oxygen, cells cannot break down food to produce ATP, the cellular currency of energy. Soon, none of their energy-dependent processes can function. Without its energy-dependent processes, a cell dies.
Neural tissues, including the brain, are particularly sensitive to oxygen deprivation. Neural tissues maintain a special cellular chemistry which must be constantly maintained through the consumption of lots and lots of energy. If ATP production stops, neural cells can begin to die within minutes.
For this reason, the body has taken many special measures to protect the heart. It is located below the strongest part of the ribcage and cushioned between the lungs. It is also surrounded by a protective membrane called the pericardium, which is filled with additional cushioning fluid.
Structure of Heart
The heart can be found at the center of the chest, underneath the sternum in a thoracic compartment. It is made up of four chambers and several valves that regulate the normal flow of blood within the body.
Two chambers called atria are located in the upper portion of the heart and receive oxygen-free blood. The valves that separate these chambers are called atrioventricular valves which is composed of the tricuspid valve on the left and the mitral valve on the right.
On the other hand, ventricles are chambers found on the lower portion of the heart; they pump oxygen-enriched blood into all organs of the body, reaching even the smallest cells. Similar to the atria, the ventricular chambers are also separated by valves. Collectively-termed as semilunar valves, these are comprised of the pulmonary and aortic valve.
The heart also has a wall that is composed of three layers: the outer layer epicardium (thin layer), the middle layer myocardium (thick layer), and the innermost layer endocardium (thin layer). The myocardium is think because it is made up of cardiac muscle fibers.