1. Circulatory System: This system is responsible for transporting blood throughout the body. Blood carries oxygen, nutrients, hormones, and other essential substances to the cells, and removes waste products like carbon dioxide. The circulatory system consists of the heart, blood vessels (arteries, veins, and capillaries), and blood itself.

2. Lymphatic System: This system works in parallel with the circulatory system. It's responsible for maintaining fluid balance in the body, absorbing fats from the digestive system, and transporting immune cells. The lymphatic system includes lymph vessels, lymph nodes, and lymph fluid.