Purkinje fibers

The endocardium forms the inner layer of the heart and consists of an epithelium (endothelium), subendothelial connective tissue and a subendocardial layer. Purkinje fibers are located in the subendocardial layer.

The endocardium forms the inner layer of the heart and consists of an epithelium (endothelium), subendothelial connective tissue and a subendocardial layer. Purkinje fibers are located in the subendocardial layer.

The endocardium forms the inner layer of the heart and consists of an epithelium (endothelium), subendothelial connective tissue and a subendocardial layer. Purkinje fibers are located in the subendocardial layer.

The endocardium forms the inner layer of the heart and consists of an epithelium (endothelium), subendothelial connective tissue and a subendocardial layer. Purkinje fibers are located in the subendocardial layer.

These images show Purkinje fibers at low and high magnifications. They are larger than cardiac muscle fibers and align in fascicles to conduct action potentials along their length.

These images show Purkinje fibers at low and high magnifications. They are larger than cardiac muscle fibers and align in fascicles to conduct action potentials along their length.

The cytoplasm of Purkinje fibers is very pale staining due to the presence of large amounts of glycogen.

Purkinje fibers have fewer myofibrils and they are mostly confined to the periphery of the cell. This distribution is apparent in the cross-sectioned fiber (blue arrow). Myofilaments are present and the banding pattern of the myofibrils is similar to that in cardiac fibers.

Purkinje fibers are modified cardiac muscle fibers and thus also have intercalated discs.

Cardiac muscle fibers, comprising the myocardium, are present beneath the endocardium.

Image from the University of Mississippi slide collection.