Final answer:
The horned lizards shoot blood from their eyes by the cooperation of the muscular system and the circulatory system.
Step-by-step explanation:
The two systems working together in horned lizards to shoot blood from their eyes are the muscular system and the circulatory system.
The major veins surrounding the lizard's eye are controlled by muscles. When the lizard contracts these muscles, blood flow is increased to the head. This increased blood flow fills a specialized membrane, similar to an eyelid, with blood.
With the help of the muscular system, the muscles in the membrane and the eye contract to shoot the blood when predators approach. Scientists believe that the blood deters predators.