it is elaborated by the secretions of the liver and then sent to the heart, which organ pumps the blood into the lungs, where carbon dioxide is exchanged for oxygen;
(it; is elaborated; by the secretions of the liver) (it; sent; to the heart; T:then) (carbon dioxide; is exchanged; for oxygen; L:the lungs)
it it carbon dioxide
is elaborated sent is exchanged
by the secretions of the liver
to the heart T:then
for oxygen L:the lungs