QS Study

Junctional Tissues of the heart

The junctional tissues are a network of fibers that convey the electrical signal between the atria and ventricles of the heart. It is the part of the conducting system of the heart forming a bridge between the atrium and ventricle of the heart, comprising the atrioventricular node and the bundle of His. They comprise the following structures: Sino-atrial (S.A.) node, Atrioventricular (A.V.) node, Bundle of His (atrioven­tricular bundle) The right and left branches of the bundle ending in the, and Purkinje fibers.

The rate of generation of impulse –

Tab: rate of generation of impulse

AVN is normally the only conducting pathway between the atria and ventricles. It is continuous with Bundle of His, which gives off a left bundle branch at the top of the interventricular septum and continues as the right bundle branch.

Fig: Junctional Tissue

The left bundle branch divides into an anterior fascicle and posterior fascicle. The branches and fascicles run subendocardially down either side of the septum and come into contact with the Purkinje system, whose fibers spread to all parts of ventricles.

The conduction system is composed mostly of modified cardiac muscle that has fewer striations and indistinct boundaries. A specialized cell of the SA node is known as P cells.