Circulatory System

The circulatory system is responsible for pumping blood throughout your body. The blood carries chemicals, including oxygen, to the other organs giving them fuel to function properly. Its central part is the heart, which does the pumping. It takes deoxidized blood and pushes it toward the lungs where it receives oxygen. The blood then travels through the arteries to the rest of the body, giving them the oxygen. The again deoxidized blood then returns to the heart through veins, which are blue because deoxidized blood is actually blue in color.

Interacting with Other Systems
The circulatory system touches every organ and system in your body. The system is connected to all of your body's cells so that it can transport oxygen efficiently. When you breathe, the circulatory system carries oxygen to your cells and carries dissolved carbon dioxide back to the lungs. 

Every cell that needs oxygen needs access to the fluids in your circulatory system. The circulatory system and its fluids are super important to your digestive system that has absorbed nutrients from your food. Guess what? Hormones created by your endocrine system are sent through the body by the circulatory system. 

Basic Parts of the Circulatory System

The core components of your circulatory system are the heart and vessels. You happen to have a four-chambered heart while other organisms may have one, two, or three chambers. The heart is the pump for the system. As blood is pumped from the heart, it passes through a system of arteries, arterioles, and then capillaries. The capillaries are the vessels that allow for most of the transfer of compounds and dissolved gases. Capillaries are very small and have thin walls to allow easier passage of compounds including nutrients, glucose, carbon dioxide, and waste products. After the capillaries, your blood passes through venules and veins. The veins lead the circulatory fluids back to the heart. That's it, the system is complete (and closed).