A conical pouch formed from the upper and left angle of the right ventricle in the chordate heart, from which the pulmonary artery arises[WP]. the anteriosuperior, smooth-walled portion of the cavity of the right ventricle, beginning at the supraventricular crest and terminates in the pulmonary trunk[MP]. [ MP:0009464 http://en.wikipedia.org/wiki/Conus_arteriosus ]