Loyola University Medical Education Network Partitioning of the Outflow Tract


The final morphological change in the heart is the partitioning of the outflow tract - -the truncus arteriosus and the conus cordis - - into the aorta and the pulmonary trunk. This is accomplished by the development of a septum that forms in the outflow tract and the emergence of the two great vessels.

The septum forms from two pairs of swellings which grow from the walls of the outflow tract. These are the truncus swellings and the conus swellings.

Truncal swellings: Right superior which grows distally and to the left. Left inferior which grows distally and to the right. Both develop at the proximal part of the truncus and proceed to grow in two directions; 1) distally towards the aortic sac and 2) into the lumen of the outflow tract where they will eventually fuse together.

Conus swellings: Right dorsal which is continuous with the right superior Left ventral which is continuous with the left inferior Like the truncal swellings, the conal swellings grow distally and towards each other, however they appear after the first pair. These conus swellings eventually fuse with the truncal swellings.

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John A. McNulty
Last Updated: April 14, 1996
Created: September 25, 1995