The bundle branches, or Tawara branches, are offshoots of the
bundle of His
The bundle of His (BH) or His bundle (HB) ( "hiss"Medical Terminology for Health Professions, Spiral bound Version'. Cengage Learning; 2016. . pp. 129–.) is a collection of heart muscle cells specialized for electrical conduction. As part of t ...
in the heart's
ventricle. They play an integral role in the
electrical conduction system of the heart
The cardiac conduction system (CCS) (also called the electrical conduction system of the heart) transmits the signals generated by the sinoatrial node – the heart's pacemaker, to cause the heart muscle to contract, and pump blood through ...
by transmitting
cardiac action potential
The cardiac action potential is a brief change in voltage ( membrane potential) across the cell membrane of heart cells. This is caused by the movement of charged atoms (called ions) between the inside and outside of the cell, through proteins c ...
s from the bundle of His to the
Purkinje fibers
The Purkinje fibers (; often incorrectly ; Purkinje tissue or subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. The Purkinje fibers are specia ...
.
Structure
There are two branches of the bundle of His: the left bundle branch and the right bundle branch, both of which are located along the
interventricular septum
The interventricular septum (IVS, or ventricular septum, or during development septum inferius) is the stout wall separating the ventricles, the lower chambers of the heart, from one another.
The ventricular septum is directed obliquely backwar ...
. The left bundle branch further divides into the left anterior fascicle and the left posterior fascicle. These structures lead to a network of thin filaments known as Purkinje fibers. They play an integral role in the electrical conduction system of the heart by transmitting cardiac action potentials to the Purkinje fibers.
Clinical significance
When a bundle branch or their fascicles becomes injured (by underlying heart disease, myocardial infarction, or cardiac surgery), it may cease to conduct electrical impulses appropriately, resulting in altered pathways for ventricular depolarization. This condition is known as a
bundle branch block
A bundle branch block is a defect in one the bundle branches in the electrical conduction system of the heart.
Anatomy and physiology
The heart's electrical activity begins in the sinoatrial node (the heart's natural pacemaker), which is situat ...
.
History
The bundle branches were separately described by Retzer and Braeunig as early as 1904, but their physiological function remained unclear and their role in the electrical conduction system of the heart remained unknown until
Sunao Tawara published his monograph on ''
Das Reizleitungssystem des Säugetierherzens'' (English: ''The Conduction System of the Mammalian Heart'') in 1906. Although Tawara's monograph had demonstrated that the branches of the bundle of His may transmit cardiac action potentials to the ventricles, the functional proof for his observation was not provided until 1910, when
Hans Eppinger and
Carl Julius Rothberger showed that cutting off both branches to induce a bilateral bundle branch block results in a complete
heart block
Heart block (HB) is a disorder in the heart's rhythm due to a fault in the natural pacemaker. This is caused by an obstruction – a block – in the electrical conduction system of the heart. Sometimes a disorder can be inherited. Despite the se ...
.
References
Further reading
*
*
{{Heart anatomy
Cardiac anatomy