Ants and insects in general, don't have lungs because humans do have hearts, but they do have an organ called a dorsal artery that pumps something called hemolymph, similar to human blood. The dorsal vessel acts as an elongated tube, and a few small muscles cover it. Ants do not have a closed circulatory system but, as humans do, a vein system and arteries. We have a free circulatory system; therefore there are no tubes to pass through anything. The dorsal tank then pumps the hemolymph around by splashing the insides of the ant with nutrients, hormones, etc. It's a perfect convenience, so ideally you get the picture. Unlike human blood, because ants do not have lungs, hemolymph does not carry oxygen. Ants instead breathe through a set of tubes known as tracheae.