The =right ventricle= (Ventriculus dexter) constitutes the
right-anterior part of the ventricular mass. It forms almost all of the
anterior border of the heart, but does not reach the apex, which is
formed entirely by the left ventricle. It extends from the third rib to
the fourth intercostal space on the left side, to the fifth rib and
space on the right side. It is somewhat triangular in outline, and is
semilunar in cross-section. Its base faces upward and a little to the
right and is connected largely with the right atrium, with which it
communicates through the atrio-ventricular orifice; but its left part
projects higher and forms the =conus arteriosus=, from which the
pulmonary artery arises. Its apex is two inches or more (ca. 5 to 6 cm.)
above the apex of the heart. On opening the cavity it is seen that the
two openings are separated by a thick rounded ridge (Crista
supraventricularis). The axis of the cavity, taken from this ridge to
the apex forms a spiral curve downward and to the right. The septal wall
is convex and faces obliquely forward and to the right.
[Illustration: