Human Heart — Core Principles
Core Principles
The human heart is a vital, four-chambered muscular organ, roughly the size of a fist, located in the thoracic cavity. It functions as a dual pump, driving blood through two distinct circuits: pulmonary circulation (to the lungs for oxygenation) and systemic circulation (to the rest of the body for oxygen and nutrient delivery).
The heart comprises two atria (receiving chambers) and two ventricles (pumping chambers), separated by septa. Unidirectional blood flow is ensured by four valves: tricuspid and bicuspid (mitral) as atrioventricular valves, and pulmonary and aortic as semilunar valves.
The heart's rhythmic contractions are initiated by its intrinsic electrical conduction system, starting with the SA node (pacemaker), followed by the AV node, Bundle of His, and Purkinje fibers. The 'lub-dub' sounds correspond to the closing of AV and semilunar valves, respectively.
Its activity is regulated by both intrinsic mechanisms and extrinsic neural and hormonal controls, ensuring continuous and efficient blood circulation essential for life.
Important Differences
vs Pulmonary vs. Systemic Circulation
| Aspect | This Topic | Pulmonary vs. Systemic Circulation |
|---|---|---|
| Originating Chamber | Right Ventricle | Left Ventricle |
| Destination | Lungs | All body tissues (except lungs) |
| Type of Blood Carried by Arteries | Deoxygenated blood (Pulmonary Artery) | Oxygenated blood (Aorta and its branches) |
| Type of Blood Carried by Veins | Oxygenated blood (Pulmonary Veins) | Deoxygenated blood (Vena Cavae) |
| Purpose | Oxygenation of blood and removal of CO2 | Delivery of O2 and nutrients, removal of wastes |
| Pressure System | Low pressure system | High pressure system |