Septomarginal trabecula

Moderator band

Interior of right side of heart. (Septomarginal trabecula visible at bottom right, but not labeled.)
Latin	trabecula septomarginalis
Gray's	subject #138 532
Dorlands/Elsevier	t_14/12815165

The septomarginal trabecula (or moderator band) is a muscular band of heart tissue found in the right ventricle. It is well-marked in sheep and some other animals, and frequently extends from the base of the anterior papillary muscle to the ventricular septum.

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From its attachments it was thought to prevent overdistension of the ventricle, and was named the "moderator band". However, more recent research has indicated that it is more properly considered part of the electrical conduction system of the heart, and in that capacity it is called the "septomarginal trabecula". The TA name is "trabecula septomarginalis".

The moderator band is often used by radiologists to more easily identify the right ventricle in prenatal ultrasound.

v • d • e Anatomy of torso, cardiovascular system: heart
Structures	atria (interatrial septum, musculi pectinati) • ventricles (interventricular septum, trabeculae carneae, chordae tendinae, papillary muscle) • valves • cusps
Regions	base • apex • grooves (coronary/atrioventricular, interatrial, anterior interventricula, posterior interventricular) • surfaces (sternocostal, diaphragmatic) • borders (right, left)
Right heart	(vena cavae, coronary sinus) → right atrium (auricle, fossa ovalis, limbus of fossa ovalis, crista terminalis, valve of the inferior vena cava, valve of the coronary sinus) → tricuspid valve → right ventricle (conus arteriosus, moderator band/septomarginal trabecula) → pulmonary valve → (pulmonary artery and pulmonary circulation)
Left heart	(pulmonary veins) → left atrium (auricle) → mitral valve → left ventricle → aortic valve (aortic sinus) → (aorta and systemic circulation)
Layers	pericardium: fibrous pericardium • serous pericardium (pericardial cavity, epicardium/visceral layer) • pericardial sinus myocardium • endocardium • cardiac skeleton (fibrous trigone, fibrous rings)
Conduction system	Cardiac pacemaker • SA node • AV node• bundle of His • Purkinje fibers