Truncus

Truncus is a Latin term meaning trunk, stem, or main axis, and it is used in medical and biological terminology to denote a central conduit or primary structure. In English-language anatomy and medicine, truncus is often part of compound names that identify a major vessel or nerve trunk.

In anatomy and embryology, truncus appears in several well-known terms. Truncus arteriosus refers to the arterial trunk that emerges from the heart before it divides into the aorta and the pulmonary trunk. In the embryo, the truncus arteriosus is the primitive outflow tract; proper septation by neural crest–derived cells separates it into the ascending aorta and the pulmonary trunk. A congenital heart defect called persistent truncus arteriosus occurs when this division fails, resulting in a single arterial trunk supplying both systemic and pulmonary circulations.

Other vascular terms include truncus brachiocephalicus (brachiocephalic trunk), a major artery that gives rise to the right common carotid and right subclavian arteries in many species, and truncus pulmonalis (pulmonary trunk), the vessel carrying blood from the right ventricle to the lungs. The word also appears in reference to the sympathetic trunk (truncus sympathicus) along the vertebral column, representing a major neural pathway.

Beyond medicine, truncus can describe the main body axis or trunk of an organism or plant in biological contexts, contrasting with limbs, appendages, or branches. The form and usage of truncus thus emphasize a central, connecting role within a biological system.