Purkinjefíbrum

The Purkinje fibers, also known as Purkinjefíbrum in some languages, are specialized cardiac muscle fibers that play a crucial role in the electrical conduction system of the heart. Named after the Czech physiologist Jan Evangelista Purkyně (also spelled Purkinje), these fibers were first described in the 19th century. They are part of the ventricular conduction system, responsible for rapidly transmitting electrical impulses across the ventricles, ensuring coordinated contraction and efficient pumping of blood.

Anatomically, Purkinje fibers originate from the bundle of His, which itself branches from the atrioventricular (AV) node. The bundle of His divides into the left and right bundle branches, which further subdivide into smaller Purkinje fibers that spread throughout the ventricular myocardium. These fibers are characterized by their large diameter and high conduction velocity, allowing rapid signal propagation compared to ordinary cardiac muscle cells.

The primary function of Purkinje fibers is to synchronize ventricular contraction. By conducting electrical impulses quickly, they ensure that the ventricles contract in a wave-like motion, starting from the apex and moving upward. This coordinated contraction maximizes the efficiency of blood ejection from the heart. Dysfunction or damage to Purkinje fibers, such as in bundle branch blocks, can disrupt this process, leading to abnormal heart rhythms or reduced cardiac output.

Histologically, Purkinje fibers contain fewer myofibrils and more glycogen than typical cardiac muscle cells, which contributes to their rapid conduction properties. They also exhibit spontaneous depolarization, though this is less pronounced than in pacemaker cells like those in the SA node. The structural and functional uniqueness of Purkinje fibers underscores their essential role in maintaining normal cardiac function.