And, muscles attached to the spider's gut and to the inside wall of the cephalothorax can contract to create a strong sucking action during feeding. Spiders have an open, blood circulatory system. This sort of blood system has a heart, arteries and veins but no capillaries. The heart is tubular with a single cavity and with valves to maintain the flow of blood always in the same direction. The spider's blood is pale blue due to the presence of haemocyanin dissolved in the lymph.
Spiders have lungs.
There are two sorts of lungs neither of which is like a human lung. Some spiders have book lungs. A book lung has a stack of soft plates called lamellae. Oxygen in the air passing between the lamellae diffuses through the tissue into the blood. Other spiders have tracheae which are breathing tubes held open by rings of chitin.